user-mode-linux-devel

Re: [uml-devel] PATCH v11

[Anton I. <ant...@ko...>]

Acknowledge, will do it this afternoon.
A. 

On 22 November 2017 11:59:35 GMT+00:00, Richard Weinberger <ri...@si...> wrote:
>Am Mittwoch, 22. November 2017, 12:57:21 CET schrieb anton.ivanov@kot-
>begemot.co.uk:
>> This revision adds EXPORT for deactivate_irq_by_fd as needed
>> by the random driver with some kernel configs
>
>Please patchs ontop of linux-next.
>Rebasing linux-next is not nice.
>
>Thanks,
>//richard
>
>-- 
>sigma star gmbh - Eduard-Bodem-Gasse 6 - 6020 Innsbruck - Austria
>ATU66964118 - FN 374287y

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Re: [uml-devel] PATCH v11

[Richard W. <ri...@si...>]

Am Mittwoch, 22. November 2017, 12:57:21 CET schrieb anton.ivanov@kot-
begemot.co.uk:
> This revision adds EXPORT for deactivate_irq_by_fd as needed
> by the random driver with some kernel configs

Please patchs ontop of linux-next.
Rebasing linux-next is not nice.

Thanks,
//richard

-- 
sigma star gmbh - Eduard-Bodem-Gasse 6 - 6020 Innsbruck - Austria
ATU66964118 - FN 374287y

[uml-devel] [PATCH v11 1/2] Epoll based IRQ controller

[<ant...@ko...>]

From: Anton Ivanov <ant...@ca...>

1. Removes the need to walk the IRQ/Device list to determine
who triggered the IRQ.
2. Improves scalability (up to several times performance
improvement for cases with 10s of devices).
3. Improves UML baseline IO performance for one disk + one NIC
use case by up to 10%.
4. Introduces write poll triggered IRQs.
5. Prerequisite for introducing high performance mmesg family
of functions in network IO.
6. Fixes RNG shutdown which was leaking a file descriptor

Signed-off-by: Anton Ivanov <ant...@ca...>
---
 arch/um/drivers/chan_kern.c       |  53 +----
 arch/um/drivers/line.c            |   2 +-
 arch/um/drivers/random.c          |  11 +-
 arch/um/drivers/ubd_kern.c        |   4 +-
 arch/um/include/shared/irq_user.h |  12 +-
 arch/um/include/shared/os.h       |  17 +-
 arch/um/kernel/irq.c              | 460 ++++++++++++++++++++++++--------------
 arch/um/os-Linux/irq.c            | 202 +++++++++--------
 8 files changed, 444 insertions(+), 317 deletions(-)

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index acbe6c67afba..05588f9466c7 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -171,56 +171,19 @@ int enable_chan(struct line *line)
 	return err;
 }
 
-/* Items are added in IRQ context, when free_irq can't be called, and
- * removed in process context, when it can.
- * This handles interrupt sources which disappear, and which need to
- * be permanently disabled.  This is discovered in IRQ context, but
- * the freeing of the IRQ must be done later.
- */
-static DEFINE_SPINLOCK(irqs_to_free_lock);
-static LIST_HEAD(irqs_to_free);
-
-void free_irqs(void)
-{
-	struct chan *chan;
-	LIST_HEAD(list);
-	struct list_head *ele;
-	unsigned long flags;
-
-	spin_lock_irqsave(&irqs_to_free_lock, flags);
-	list_splice_init(&irqs_to_free, &list);
-	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-
-	list_for_each(ele, &list) {
-		chan = list_entry(ele, struct chan, free_list);
-
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
-}
-
 static void close_one_chan(struct chan *chan, int delay_free_irq)
 {
-	unsigned long flags;
-
 	if (!chan->opened)
 		return;
 
-	if (delay_free_irq) {
-		spin_lock_irqsave(&irqs_to_free_lock, flags);
-		list_add(&chan->free_list, &irqs_to_free);
-		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-	}
-	else {
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
+    /* we can safely call free now - it will be marked
+     *  as free and freed once the IRQ stopped processing
+     */
+	if (chan->input && chan->enabled)
+		um_free_irq(chan->line->driver->read_irq, chan);
+	if (chan->output && chan->enabled)
+		um_free_irq(chan->line->driver->write_irq, chan);
+	chan->enabled = 0;
 	if (chan->ops->close != NULL)
 		(*chan->ops->close)(chan->fd, chan->data);
 
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 366e57f5e8d6..8d80b27502e6 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -284,7 +284,7 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	if (err)
 		return err;
 	if (output)
-		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
+		err = um_request_irq(driver->write_irq, fd, IRQ_NONE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
 	return err;
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 37c51a6be690..778a0e52d5a5 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -13,6 +13,7 @@
 #include <linux/miscdevice.h>
 #include <linux/delay.h>
 #include <linux/uaccess.h>
+#include <init.h>
 #include <irq_kern.h>
 #include <os.h>
 
@@ -154,7 +155,14 @@ static int __init rng_init (void)
 /*
  * rng_cleanup - shutdown RNG module
  */
-static void __exit rng_cleanup (void)
+
+static void cleanup(void)
+{
+	free_irq_by_fd(random_fd);
+	os_close_file(random_fd);
+}
+
+static void __exit rng_cleanup(void)
 {
 	os_close_file(random_fd);
 	misc_deregister (&rng_miscdev);
@@ -162,6 +170,7 @@ static void __exit rng_cleanup (void)
 
 module_init (rng_init);
 module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
 
 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index b55fe9bf5d3e..d4e8c497ae86 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1587,11 +1587,11 @@ int io_thread(void *arg)
 
 		do {
 			res = os_write_file(kernel_fd, ((char *) io_req_buffer) + written, n);
-			if (res > 0) {
+			if (res >= 0) {
 				written += res;
 			} else {
 				if (res != -EAGAIN) {
-					printk("io_thread - read failed, fd = %d, "
+					printk("io_thread - write failed, fd = %d, "
 					       "err = %d\n", kernel_fd, -n);
 				}
 			}
diff --git a/arch/um/include/shared/irq_user.h b/arch/um/include/shared/irq_user.h
index df5633053957..a7a6120f19d5 100644
--- a/arch/um/include/shared/irq_user.h
+++ b/arch/um/include/shared/irq_user.h
@@ -7,6 +7,7 @@
 #define __IRQ_USER_H__
 
 #include <sysdep/ptrace.h>
+#include <stdbool.h>
 
 struct irq_fd {
 	struct irq_fd *next;
@@ -15,10 +16,17 @@ struct irq_fd {
 	int type;
 	int irq;
 	int events;
-	int current_events;
+	bool active;
+	bool pending;
+	bool purge;
 };
 
-enum { IRQ_READ, IRQ_WRITE };
+#define IRQ_READ  0
+#define IRQ_WRITE 1
+#define IRQ_NONE 2
+#define MAX_IRQ_TYPE (IRQ_NONE + 1)
+
+
 
 struct siginfo;
 extern void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 574e03fc7ba2..edbe6563d5c5 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -290,15 +290,16 @@ extern void halt_skas(void);
 extern void reboot_skas(void);
 
 /* irq.c */
-extern int os_waiting_for_events(struct irq_fd *active_fds);
-extern int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds);
-extern void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2);
-extern void os_free_irq_later(struct irq_fd *active_fds,
-		int irq, void *dev_id);
-extern int os_get_pollfd(int i);
-extern void os_set_pollfd(int i, int fd);
+extern int os_waiting_for_events_epoll(void);
+extern void *os_epoll_get_data_pointer(int index);
+extern int os_epoll_triggered(int index, int events);
+extern int os_event_mask(int irq_type);
+extern int os_setup_epoll(void);
+extern int os_add_epoll_fd(int events, int fd, void *data);
+extern int os_mod_epoll_fd(int events, int fd, void *data);
+extern int os_del_epoll_fd(int fd);
 extern void os_set_ioignore(void);
+extern void os_close_epoll_fd(void);
 
 /* sigio.c */
 extern int add_sigio_fd(int fd);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 23cb9350d47e..980148d56537 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -1,4 +1,6 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
@@ -16,243 +18,361 @@
 #include <as-layout.h>
 #include <kern_util.h>
 #include <os.h>
+#include <irq_user.h>
 
-/*
- * This list is accessed under irq_lock, except in sigio_handler,
- * where it is safe from being modified.  IRQ handlers won't change it -
- * if an IRQ source has vanished, it will be freed by free_irqs just
- * before returning from sigio_handler.  That will process a separate
- * list of irqs to free, with its own locking, coming back here to
- * remove list elements, taking the irq_lock to do so.
+
+/* When epoll triggers we do not know why it did so
+ * we can also have different IRQs for read and write.
+ * This is why we keep a small irq_fd array for each fd -
+ * one entry per IRQ type
  */
-static struct irq_fd *active_fds = NULL;
-static struct irq_fd **last_irq_ptr = &active_fds;
 
-extern void free_irqs(void);
+struct irq_entry {
+	struct irq_entry *next;
+	int fd;
+	struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
+};
+
+static struct irq_entry *active_fds;
+
+static DEFINE_SPINLOCK(irq_lock);
+
+static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
+{
+/*
+ * irq->active guards against reentry
+ * irq->pending accumulates pending requests
+ * if pending is raised the irq_handler is re-run
+ * until pending is cleared
+ */
+	if (irq->active) {
+		irq->active = false;
+		do {
+			irq->pending = false;
+			do_IRQ(irq->irq, regs);
+		} while (irq->pending && (!irq->purge));
+		if (!irq->purge)
+			irq->active = true;
+	} else {
+		irq->pending = true;
+	}
+}
 
 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
-	struct irq_fd *irq_fd;
-	int n;
+	struct irq_entry *irq_entry;
+	struct irq_fd *irq;
+
+	int n, i, j;
 
 	while (1) {
-		n = os_waiting_for_events(active_fds);
+		/* This is now lockless - epoll keeps back-referencesto the irqs
+		 * which have trigger it so there is no need to walk the irq
+		 * list and lock it every time. We avoid locking by turning off
+		 * IO for a specific fd by executing os_del_epoll_fd(fd) before
+		 * we do any changes to the actual data structures
+		 */
+		n = os_waiting_for_events_epoll();
+
 		if (n <= 0) {
 			if (n == -EINTR)
 				continue;
-			else break;
+			else
+				break;
 		}
 
-		for (irq_fd = active_fds; irq_fd != NULL;
-		     irq_fd = irq_fd->next) {
-			if (irq_fd->current_events != 0) {
-				irq_fd->current_events = 0;
-				do_IRQ(irq_fd->irq, regs);
+		for (i = 0; i < n ; i++) {
+			/* Epoll back reference is the entry with 3 irq_fd
+			 * leaves - one for each irq type.
+			 */
+			irq_entry = (struct irq_entry *)
+				os_epoll_get_data_pointer(i);
+			for (j = 0; j < MAX_IRQ_TYPE ; j++) {
+				irq = irq_entry->irq_array[j];
+				if (irq == NULL)
+					continue;
+				if (os_epoll_triggered(i, irq->events) > 0)
+					irq_io_loop(irq, regs);
+				if (irq->purge) {
+					irq_entry->irq_array[j] = NULL;
+					kfree(irq);
+				}
 			}
 		}
 	}
+}
+
+static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
+{
+	int i;
+	int events = 0;
+	struct irq_fd *irq;
 
-	free_irqs();
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		irq = irq_entry->irq_array[i];
+		if (irq != NULL)
+			events = irq->events | events;
+	}
+	if (events > 0) {
+	/* os_add_epoll will call os_mod_epoll if this already exists */
+		return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
+	}
+	/* No events - delete */
+	return os_del_epoll_fd(irq_entry->fd);
 }
 
-static DEFINE_SPINLOCK(irq_lock);
+
 
 static int activate_fd(int irq, int fd, int type, void *dev_id)
 {
-	struct pollfd *tmp_pfd;
-	struct irq_fd *new_fd, *irq_fd;
+	struct irq_fd *new_fd;
+	struct irq_entry *irq_entry;
+	int i, err, events;
 	unsigned long flags;
-	int events, err, n;
 
 	err = os_set_fd_async(fd);
 	if (err < 0)
 		goto out;
 
-	err = -ENOMEM;
-	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
-	if (new_fd == NULL)
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
 
-	if (type == IRQ_READ)
-		events = UM_POLLIN | UM_POLLPRI;
-	else events = UM_POLLOUT;
-	*new_fd = ((struct irq_fd) { .next  		= NULL,
-				     .id 		= dev_id,
-				     .fd 		= fd,
-				     .type 		= type,
-				     .irq 		= irq,
-				     .events 		= events,
-				     .current_events 	= 0 } );
+	/* Check if we have an entry for this fd */
 
 	err = -EBUSY;
-	spin_lock_irqsave(&irq_lock, flags);
-	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
-		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
-			printk(KERN_ERR "Registering fd %d twice\n", fd);
-			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
-			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
-			       dev_id);
+	for (irq_entry = active_fds;
+		irq_entry != NULL; irq_entry = irq_entry->next) {
+		if (irq_entry->fd == fd)
+			break;
+	}
+
+	if (irq_entry == NULL) {
+		/* This needs to be atomic as it may be called from an
+		 * IRQ context.
+		 */
+		irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
+		if (irq_entry == NULL) {
+			printk(KERN_ERR
+				"Failed to allocate new IRQ entry\n");
 			goto out_unlock;
 		}
+		irq_entry->fd = fd;
+		for (i = 0; i < MAX_IRQ_TYPE; i++)
+			irq_entry->irq_array[i] = NULL;
+		irq_entry->next = active_fds;
+		active_fds = irq_entry;
 	}
 
-	if (type == IRQ_WRITE)
-		fd = -1;
-
-	tmp_pfd = NULL;
-	n = 0;
+	/* Check if we are trying to re-register an interrupt for a
+	 * particular fd
+	 */
 
-	while (1) {
-		n = os_create_pollfd(fd, events, tmp_pfd, n);
-		if (n == 0)
-			break;
+	if (irq_entry->irq_array[type] != NULL) {
+		printk(KERN_ERR
+			"Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
+			irq, fd, type, dev_id
+		);
+		goto out_unlock;
+	} else {
+		/* New entry for this fd */
+
+		err = -ENOMEM;
+		new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
+		if (new_fd == NULL)
+			goto out_unlock;
 
-		/*
-		 * n > 0
-		 * It means we couldn't put new pollfd to current pollfds
-		 * and tmp_fds is NULL or too small for new pollfds array.
-		 * Needed size is equal to n as minimum.
-		 *
-		 * Here we have to drop the lock in order to call
-		 * kmalloc, which might sleep.
-		 * If something else came in and changed the pollfds array
-		 * so we will not be able to put new pollfd struct to pollfds
-		 * then we free the buffer tmp_fds and try again.
+		events = os_event_mask(type);
+
+		*new_fd = ((struct irq_fd) {
+			.id		= dev_id,
+			.irq		= irq,
+			.type		= type,
+			.events		= events,
+			.active		= true,
+			.pending	= false,
+			.purge		= false
+		});
+		/* Turn off any IO on this fd - allows us to
+		 * avoid locking the IRQ loop
 		 */
-		spin_unlock_irqrestore(&irq_lock, flags);
-		kfree(tmp_pfd);
-
-		tmp_pfd = kmalloc(n, GFP_KERNEL);
-		if (tmp_pfd == NULL)
-			goto out_kfree;
-
-		spin_lock_irqsave(&irq_lock, flags);
+		os_del_epoll_fd(irq_entry->fd);
+		irq_entry->irq_array[type] = new_fd;
 	}
 
-	*last_irq_ptr = new_fd;
-	last_irq_ptr = &new_fd->next;
-
+	/* Turn back IO on with the correct (new) IO event mask */
+	assign_epoll_events_to_irq(irq_entry);
 	spin_unlock_irqrestore(&irq_lock, flags);
-
-	/*
-	 * This calls activate_fd, so it has to be outside the critical
-	 * section.
-	 */
-	maybe_sigio_broken(fd, (type == IRQ_READ));
+	maybe_sigio_broken(fd, (type != IRQ_NONE));
 
 	return 0;
-
- out_unlock:
+out_unlock:
 	spin_unlock_irqrestore(&irq_lock, flags);
- out_kfree:
-	kfree(new_fd);
- out:
+out:
 	return err;
 }
 
-static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
+/*
+ * Walk the IRQ list and dispose of any unused entries.
+ * Should be done under irq_lock.
+ */
+
+static void garbage_collect_irq_entries(void)
 {
-	unsigned long flags;
+	int i;
+	bool reap;
+	struct irq_entry *walk;
+	struct irq_entry *previous = NULL;
+	struct irq_entry *to_free;
 
-	spin_lock_irqsave(&irq_lock, flags);
-	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
-	spin_unlock_irqrestore(&irq_lock, flags);
+	if (active_fds == NULL)
+		return;
+	walk = active_fds;
+	while (walk != NULL) {
+		reap = true;
+		for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+			if (walk->irq_array[i] != NULL) {
+				reap = false;
+				break;
+			}
+		}
+		if (reap) {
+			if (previous == NULL)
+				active_fds = walk->next;
+			else
+				previous->next = walk->next;
+			to_free = walk;
+		} else {
+			to_free = NULL;
+		}
+		walk = walk->next;
+		if (to_free != NULL)
+			kfree(to_free);
+	}
 }
 
-struct irq_and_dev {
-	int irq;
-	void *dev;
-};
+/*
+ * Walk the IRQ list and get the descriptor for our FD
+ */
 
-static int same_irq_and_dev(struct irq_fd *irq, void *d)
+static struct irq_entry *get_irq_entry_by_fd(int fd)
 {
-	struct irq_and_dev *data = d;
+	struct irq_entry *walk = active_fds;
 
-	return ((irq->irq == data->irq) && (irq->id == data->dev));
+	while (walk != NULL) {
+		if (walk->fd == fd)
+			return walk;
+		walk = walk->next;
+	}
+	return NULL;
 }
 
-static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
-{
-	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
-							  .dev  = dev });
 
-	free_irq_by_cb(same_irq_and_dev, &data);
-}
+/*
+ * Walk the IRQ list and dispose of an entry for a specific
+ * device, fd and number. Note - if sharing an IRQ for read
+ * and writefor the same FD it will be disposed in either case.
+ * If this behaviour is undesirable use different IRQ ids.
+ */
 
-static int same_fd(struct irq_fd *irq, void *fd)
-{
-	return (irq->fd == *((int *)fd));
-}
+#define IGNORE_IRQ 1
+#define IGNORE_DEV (1<<1)
 
-void free_irq_by_fd(int fd)
+static void do_free_by_irq_and_dev(
+	struct irq_entry *irq_entry,
+	unsigned int irq,
+	void *dev,
+	int flags
+)
 {
-	free_irq_by_cb(same_fd, &fd);
+	int i;
+	struct irq_fd *to_free;
+
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		if (irq_entry->irq_array[i] != NULL) {
+			if (
+			((flags & IGNORE_IRQ) ||
+				(irq_entry->irq_array[i]->irq == irq)) &&
+			((flags & IGNORE_DEV) ||
+				(irq_entry->irq_array[i]->id == dev))
+			) {
+				/* Turn off any IO on this fd - allows us to
+				 * avoid locking the IRQ loop
+				 */
+				os_del_epoll_fd(irq_entry->fd);
+				to_free = irq_entry->irq_array[i];
+				irq_entry->irq_array[i] = NULL;
+				assign_epoll_events_to_irq(irq_entry);
+				if (to_free->active)
+					to_free->purge = true;
+				else
+					kfree(to_free);
+			}
+		}
+	}
 }
 
-/* Must be called with irq_lock held */
-static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
+void free_irq_by_fd(int fd)
 {
-	struct irq_fd *irq;
-	int i = 0;
-	int fdi;
+	struct irq_entry *to_free;
+	unsigned long flags;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		if ((irq->fd == fd) && (irq->irq == irqnum))
-			break;
-		i++;
-	}
-	if (irq == NULL) {
-		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
-		       fd);
-		goto out;
-	}
-	fdi = os_get_pollfd(i);
-	if ((fdi != -1) && (fdi != fd)) {
-		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
-		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
-		       fdi, fd);
-		irq = NULL;
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
 	}
-	*index_out = i;
- out:
-	return irq;
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
 }
 
-void reactivate_fd(int fd, int irqnum)
+static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irq,
+			dev,
+			0
+		);
+		to_free = to_free->next;
 	}
-	os_set_pollfd(i, irq->fd);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
+}
 
-	add_sigio_fd(fd);
+
+void reactivate_fd(int fd, int irqnum)
+{
+	/** NOP - we do auto-EOI now **/
 }
 
 void deactivate_fd(int fd, int irqnum)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
+	os_del_epoll_fd(fd);
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irqnum,
+			NULL,
+			IGNORE_DEV
+		);
 	}
-
-	os_set_pollfd(i, -1);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
-
 	ignore_sigio_fd(fd);
 }
 EXPORT_SYMBOL(deactivate_fd);
@@ -265,17 +385,28 @@ EXPORT_SYMBOL(deactivate_fd);
  */
 int deactivate_all_fds(void)
 {
-	struct irq_fd *irq;
-	int err;
+	unsigned long flags;
+	struct irq_entry *to_free;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		err = os_clear_fd_async(irq->fd);
-		if (err)
-			return err;
-	}
-	/* If there is a signal already queued, after unblocking ignore it */
+	spin_lock_irqsave(&irq_lock, flags);
+	/* Stop IO. The IRQ loop has no lock so this is our
+	 * only way of making sure we are safe to dispose
+	 * of all IRQ handlers
+	 */
 	os_set_ioignore();
-
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
+		to_free = to_free->next;
+	}
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
+	os_close_epoll_fd();
 	return 0;
 }
 
@@ -353,8 +484,11 @@ void __init init_IRQ(void)
 
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
+
 	for (i = 1; i < NR_IRQS; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
+	/* Initialize EPOLL Loop */
+	os_setup_epoll();
 }
 
 /*
diff --git a/arch/um/os-Linux/irq.c b/arch/um/os-Linux/irq.c
index b9afb74b79ad..365823010346 100644
--- a/arch/um/os-Linux/irq.c
+++ b/arch/um/os-Linux/irq.c
@@ -1,135 +1,147 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
 
 #include <stdlib.h>
 #include <errno.h>
-#include <poll.h>
+#include <sys/epoll.h>
 #include <signal.h>
 #include <string.h>
 #include <irq_user.h>
 #include <os.h>
 #include <um_malloc.h>
 
+/* Epoll support */
+
+static int epollfd = -1;
+
+#define MAX_EPOLL_EVENTS 64
+
+static struct epoll_event epoll_events[MAX_EPOLL_EVENTS];
+
+/* Helper to return an Epoll data pointer from an epoll event structure.
+ * We need to keep this one on the userspace side to keep includes separate
+ */
+
+void *os_epoll_get_data_pointer(int index)
+{
+	return epoll_events[index].data.ptr;
+}
+
+/* Helper to compare events versus the events in the epoll structure.
+ * Same as above - needs to be on the userspace side
+ */
+
+
+int os_epoll_triggered(int index, int events)
+{
+	return epoll_events[index].events & events;
+}
+/* Helper to set the event mask.
+ * The event mask is opaque to the kernel side, because it does not have
+ * access to the right includes/defines for EPOLL constants.
+ */
+
+int os_event_mask(int irq_type)
+{
+	if (irq_type == IRQ_READ)
+		return EPOLLIN | EPOLLPRI;
+	if (irq_type == IRQ_WRITE)
+		return EPOLLOUT;
+	return 0;
+}
+
 /*
- * Locked by irq_lock in arch/um/kernel/irq.c.  Changed by os_create_pollfd
- * and os_free_irq_by_cb, which are called under irq_lock.
+ * Initial Epoll Setup
  */
-static struct pollfd *pollfds = NULL;
-static int pollfds_num = 0;
-static int pollfds_size = 0;
+int os_setup_epoll(void)
+{
+	epollfd = epoll_create(MAX_EPOLL_EVENTS);
+	return epollfd;
+}
 
-int os_waiting_for_events(struct irq_fd *active_fds)
+/*
+ * Helper to run the actual epoll_wait
+ */
+int os_waiting_for_events_epoll(void)
 {
-	struct irq_fd *irq_fd;
-	int i, n, err;
+	int n, err;
 
-	n = poll(pollfds, pollfds_num, 0);
+	n = epoll_wait(epollfd,
+		(struct epoll_event *) &epoll_events, MAX_EPOLL_EVENTS, 0);
 	if (n < 0) {
 		err = -errno;
 		if (errno != EINTR)
-			printk(UM_KERN_ERR "os_waiting_for_events:"
-			       " poll returned %d, errno = %d\n", n, errno);
+			printk(
+				UM_KERN_ERR "os_waiting_for_events:"
+				" epoll returned %d, error = %s\n", n,
+				strerror(errno)
+			);
 		return err;
 	}
-
-	if (n == 0)
-		return 0;
-
-	irq_fd = active_fds;
-
-	for (i = 0; i < pollfds_num; i++) {
-		if (pollfds[i].revents != 0) {
-			irq_fd->current_events = pollfds[i].revents;
-			pollfds[i].fd = -1;
-		}
-		irq_fd = irq_fd->next;
-	}
 	return n;
 }
 
-int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds)
-{
-	if (pollfds_num == pollfds_size) {
-		if (size_tmpfds <= pollfds_size * sizeof(pollfds[0])) {
-			/* return min size needed for new pollfds area */
-			return (pollfds_size + 1) * sizeof(pollfds[0]);
-		}
-
-		if (pollfds != NULL) {
-			memcpy(tmp_pfd, pollfds,
-			       sizeof(pollfds[0]) * pollfds_size);
-			/* remove old pollfds */
-			kfree(pollfds);
-		}
-		pollfds = tmp_pfd;
-		pollfds_size++;
-	} else
-		kfree(tmp_pfd);	/* remove not used tmp_pfd */
-
-	pollfds[pollfds_num] = ((struct pollfd) { .fd		= fd,
-						  .events	= events,
-						  .revents	= 0 });
-	pollfds_num++;
-
-	return 0;
-}
 
-void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2)
+/*
+ * Helper to add a fd to epoll
+ */
+int os_add_epoll_fd(int events, int fd, void *data)
 {
-	struct irq_fd **prev;
-	int i = 0;
-
-	prev = &active_fds;
-	while (*prev != NULL) {
-		if ((*test)(*prev, arg)) {
-			struct irq_fd *old_fd = *prev;
-			if ((pollfds[i].fd != -1) &&
-			    (pollfds[i].fd != (*prev)->fd)) {
-				printk(UM_KERN_ERR "os_free_irq_by_cb - "
-				       "mismatch between active_fds and "
-				       "pollfds, fd %d vs %d\n",
-				       (*prev)->fd, pollfds[i].fd);
-				goto out;
-			}
-
-			pollfds_num--;
-
-			/*
-			 * This moves the *whole* array after pollfds[i]
-			 * (though it doesn't spot as such)!
-			 */
-			memmove(&pollfds[i], &pollfds[i + 1],
-			       (pollfds_num - i) * sizeof(pollfds[0]));
-			if (*last_irq_ptr2 == &old_fd->next)
-				*last_irq_ptr2 = prev;
-
-			*prev = (*prev)->next;
-			if (old_fd->type == IRQ_WRITE)
-				ignore_sigio_fd(old_fd->fd);
-			kfree(old_fd);
-			continue;
-		}
-		prev = &(*prev)->next;
-		i++;
-	}
- out:
-	return;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events | EPOLLET;
+	result = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
+	if ((result) && (errno == EEXIST))
+		result = os_mod_epoll_fd(events, fd, data);
+	if (result)
+		printk("epollctl add err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-int os_get_pollfd(int i)
+/*
+ * Helper to mod the fd event mask and/or data backreference
+ */
+int os_mod_epoll_fd(int events, int fd, void *data)
 {
-	return pollfds[i].fd;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events;
+	result = epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
+	if (result)
+		printk(UM_KERN_ERR
+			"epollctl mod err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-void os_set_pollfd(int i, int fd)
+/*
+ * Helper to delete the epoll fd
+ */
+int os_del_epoll_fd(int fd)
 {
-	pollfds[i].fd = fd;
+	struct epoll_event event;
+	int result;
+	/* This is quiet as we use this as IO ON/OFF - so it is often
+	 * invoked on a non-existent fd
+	 */
+	result = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
+	return result;
 }
 
 void os_set_ioignore(void)
 {
 	signal(SIGIO, SIG_IGN);
 }
+
+void os_close_epoll_fd(void)
+{
+	/* Needed so we do not leak an fd when rebooting */
+	os_close_file(epollfd);
+}
-- 
2.11.0

[uml-devel] PATCH v11

[<ant...@ko...>]

This revision adds EXPORT for deactivate_irq_by_fd as needed
by the random driver with some kernel configs

[uml-devel] [uml:for-linus-4.15-rc1 6/6] vector_user.c:(.text+0x397): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking

[kbuild t. r. <fen...@in...>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git for-linus-4.15-rc1
head:   ad1f62ab2bd43b962127af760d59a25ae1c93681
commit: ad1f62ab2bd43b962127af760d59a25ae1c93681 [6/6] High Performance UML Vector Network Driver
config: um-allyesconfig (attached as .config)
compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
reproduce:
        git checkout ad1f62ab2bd43b962127af760d59a25ae1c93681
        # save the attached .config to linux build tree
        make ARCH=um 

All warnings (new ones prefixed by >>):

   arch/um/drivers/vde.o: In function `vde_open_real':
   (.text+0x951): warning: Using 'getgrnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   (.text+0x79c): warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   arch/um/drivers/vector_user.o: In function `user_init_socket_fds':
>> vector_user.c:(.text+0x397): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   arch/um/drivers/pcap.o: In function `pcap_nametoaddr':
   (.text+0xdef5): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   arch/um/drivers/pcap.o: In function `pcap_nametonetaddr':
   (.text+0xdf95): warning: Using 'getnetbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   arch/um/drivers/pcap.o: In function `pcap_nametoproto':
   (.text+0xe1b5): warning: Using 'getprotobyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   arch/um/drivers/pcap.o: In function `pcap_nametoport':
   (.text+0xdfe7): warning: Using 'getservbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
   drivers/auxdisplay/img-ascii-lcd.o: In function `img_ascii_lcd_probe':
   img-ascii-lcd.c:(.text+0x771): undefined reference to `devm_ioremap_resource'
   collect2: error: ld returned 1 exit status

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Re: [uml-devel] [uml:for-linus-4.15-rc1 5/6] ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!

[Anton I. <ant...@ko...>]

irq.c needs an EXPORT_SYMBOL(free_irq_by_fd);

Amended patch coming up shortly.

A.


On 11/22/17 09:33, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git for-linus-4.15-rc1
> head:   ad1f62ab2bd43b962127af760d59a25ae1c93681
> commit: d4560bdc6d38f5c3bf5889fd95c954b6b5949fab [5/6] Epoll based IRQ controller
> config: um-allmodconfig (attached as .config)
> compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
> reproduce:
>          git checkout d4560bdc6d38f5c3bf5889fd95c954b6b5949fab
>          # save the attached .config to linux build tree
>          make ARCH=um
>
> All errors (new ones prefixed by >>):
>
>     ERROR: "devm_ioremap_resource" [drivers/auxdisplay/img-ascii-lcd.ko] undefined!
>>> ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Re: [uml-devel] [uml:for-linus-4.15-rc1 5/6] ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!

[Anton I. <ant...@ko...>]

weird

free_irq_by_fd is defined by irq_user which is included by os.h and that 
is included by random.c

I do not quite see how it could end up undefined.

A.


On 11/22/17 09:33, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git for-linus-4.15-rc1
> head:   ad1f62ab2bd43b962127af760d59a25ae1c93681
> commit: d4560bdc6d38f5c3bf5889fd95c954b6b5949fab [5/6] Epoll based IRQ controller
> config: um-allmodconfig (attached as .config)
> compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
> reproduce:
>          git checkout d4560bdc6d38f5c3bf5889fd95c954b6b5949fab
>          # save the attached .config to linux build tree
>          make ARCH=um
>
> All errors (new ones prefixed by >>):
>
>     ERROR: "devm_ioremap_resource" [drivers/auxdisplay/img-ascii-lcd.ko] undefined!
>>> ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
>
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>
>
> _______________________________________________
> User-mode-linux-devel mailing list
> Use...@li...
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel

[uml-devel] [uml:for-linus-4.15-rc1 5/6] ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!

[kbuild t. r. <fen...@in...>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git for-linus-4.15-rc1
head:   ad1f62ab2bd43b962127af760d59a25ae1c93681
commit: d4560bdc6d38f5c3bf5889fd95c954b6b5949fab [5/6] Epoll based IRQ controller
config: um-allmodconfig (attached as .config)
compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
reproduce:
        git checkout d4560bdc6d38f5c3bf5889fd95c954b6b5949fab
        # save the attached .config to linux build tree
        make ARCH=um 

All errors (new ones prefixed by >>):

   ERROR: "devm_ioremap_resource" [drivers/auxdisplay/img-ascii-lcd.ko] undefined!
>> ERROR: "free_irq_by_fd" [arch/um/drivers/random.ko] undefined!

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[uml-devel] [PATCH v10 1/2] Epoll based IRQ controller

[<ant...@ko...>]

From: Anton Ivanov <ant...@ca...>

1. Removes the need to walk the IRQ/Device list to determine
who triggered the IRQ.
2. Improves scalability (up to several times performance
improvement for cases with 10s of devices).
3. Improves UML baseline IO performance for one disk + one NIC
use case by up to 10%.
4. Introduces write poll triggered IRQs.
5. Prerequisite for introducing high performance mmesg family
of functions in network IO.
6. Fixes RNG shutdown which was leaking a file descriptor

Signed-off-by: Anton Ivanov <ant...@ca...>
---
 arch/um/drivers/chan_kern.c       |  53 +----
 arch/um/drivers/line.c            |   2 +-
 arch/um/drivers/random.c          |  11 +-
 arch/um/drivers/ubd_kern.c        |   4 +-
 arch/um/include/shared/irq_user.h |  12 +-
 arch/um/include/shared/os.h       |  17 +-
 arch/um/kernel/irq.c              | 460 ++++++++++++++++++++++++--------------
 arch/um/os-Linux/irq.c            | 202 +++++++++--------
 8 files changed, 444 insertions(+), 317 deletions(-)

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index acbe6c67afba..05588f9466c7 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -171,56 +171,19 @@ int enable_chan(struct line *line)
 	return err;
 }
 
-/* Items are added in IRQ context, when free_irq can't be called, and
- * removed in process context, when it can.
- * This handles interrupt sources which disappear, and which need to
- * be permanently disabled.  This is discovered in IRQ context, but
- * the freeing of the IRQ must be done later.
- */
-static DEFINE_SPINLOCK(irqs_to_free_lock);
-static LIST_HEAD(irqs_to_free);
-
-void free_irqs(void)
-{
-	struct chan *chan;
-	LIST_HEAD(list);
-	struct list_head *ele;
-	unsigned long flags;
-
-	spin_lock_irqsave(&irqs_to_free_lock, flags);
-	list_splice_init(&irqs_to_free, &list);
-	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-
-	list_for_each(ele, &list) {
-		chan = list_entry(ele, struct chan, free_list);
-
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
-}
-
 static void close_one_chan(struct chan *chan, int delay_free_irq)
 {
-	unsigned long flags;
-
 	if (!chan->opened)
 		return;
 
-	if (delay_free_irq) {
-		spin_lock_irqsave(&irqs_to_free_lock, flags);
-		list_add(&chan->free_list, &irqs_to_free);
-		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-	}
-	else {
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
+    /* we can safely call free now - it will be marked
+     *  as free and freed once the IRQ stopped processing
+     */
+	if (chan->input && chan->enabled)
+		um_free_irq(chan->line->driver->read_irq, chan);
+	if (chan->output && chan->enabled)
+		um_free_irq(chan->line->driver->write_irq, chan);
+	chan->enabled = 0;
 	if (chan->ops->close != NULL)
 		(*chan->ops->close)(chan->fd, chan->data);
 
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 366e57f5e8d6..8d80b27502e6 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -284,7 +284,7 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	if (err)
 		return err;
 	if (output)
-		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
+		err = um_request_irq(driver->write_irq, fd, IRQ_NONE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
 	return err;
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 37c51a6be690..778a0e52d5a5 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -13,6 +13,7 @@
 #include <linux/miscdevice.h>
 #include <linux/delay.h>
 #include <linux/uaccess.h>
+#include <init.h>
 #include <irq_kern.h>
 #include <os.h>
 
@@ -154,7 +155,14 @@ static int __init rng_init (void)
 /*
  * rng_cleanup - shutdown RNG module
  */
-static void __exit rng_cleanup (void)
+
+static void cleanup(void)
+{
+	free_irq_by_fd(random_fd);
+	os_close_file(random_fd);
+}
+
+static void __exit rng_cleanup(void)
 {
 	os_close_file(random_fd);
 	misc_deregister (&rng_miscdev);
@@ -162,6 +170,7 @@ static void __exit rng_cleanup (void)
 
 module_init (rng_init);
 module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
 
 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index b55fe9bf5d3e..d4e8c497ae86 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1587,11 +1587,11 @@ int io_thread(void *arg)
 
 		do {
 			res = os_write_file(kernel_fd, ((char *) io_req_buffer) + written, n);
-			if (res > 0) {
+			if (res >= 0) {
 				written += res;
 			} else {
 				if (res != -EAGAIN) {
-					printk("io_thread - read failed, fd = %d, "
+					printk("io_thread - write failed, fd = %d, "
 					       "err = %d\n", kernel_fd, -n);
 				}
 			}
diff --git a/arch/um/include/shared/irq_user.h b/arch/um/include/shared/irq_user.h
index df5633053957..a7a6120f19d5 100644
--- a/arch/um/include/shared/irq_user.h
+++ b/arch/um/include/shared/irq_user.h
@@ -7,6 +7,7 @@
 #define __IRQ_USER_H__
 
 #include <sysdep/ptrace.h>
+#include <stdbool.h>
 
 struct irq_fd {
 	struct irq_fd *next;
@@ -15,10 +16,17 @@ struct irq_fd {
 	int type;
 	int irq;
 	int events;
-	int current_events;
+	bool active;
+	bool pending;
+	bool purge;
 };
 
-enum { IRQ_READ, IRQ_WRITE };
+#define IRQ_READ  0
+#define IRQ_WRITE 1
+#define IRQ_NONE 2
+#define MAX_IRQ_TYPE (IRQ_NONE + 1)
+
+
 
 struct siginfo;
 extern void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 574e03fc7ba2..edbe6563d5c5 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -290,15 +290,16 @@ extern void halt_skas(void);
 extern void reboot_skas(void);
 
 /* irq.c */
-extern int os_waiting_for_events(struct irq_fd *active_fds);
-extern int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds);
-extern void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2);
-extern void os_free_irq_later(struct irq_fd *active_fds,
-		int irq, void *dev_id);
-extern int os_get_pollfd(int i);
-extern void os_set_pollfd(int i, int fd);
+extern int os_waiting_for_events_epoll(void);
+extern void *os_epoll_get_data_pointer(int index);
+extern int os_epoll_triggered(int index, int events);
+extern int os_event_mask(int irq_type);
+extern int os_setup_epoll(void);
+extern int os_add_epoll_fd(int events, int fd, void *data);
+extern int os_mod_epoll_fd(int events, int fd, void *data);
+extern int os_del_epoll_fd(int fd);
 extern void os_set_ioignore(void);
+extern void os_close_epoll_fd(void);
 
 /* sigio.c */
 extern int add_sigio_fd(int fd);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 23cb9350d47e..980148d56537 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -1,4 +1,6 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
@@ -16,243 +18,361 @@
 #include <as-layout.h>
 #include <kern_util.h>
 #include <os.h>
+#include <irq_user.h>
 
-/*
- * This list is accessed under irq_lock, except in sigio_handler,
- * where it is safe from being modified.  IRQ handlers won't change it -
- * if an IRQ source has vanished, it will be freed by free_irqs just
- * before returning from sigio_handler.  That will process a separate
- * list of irqs to free, with its own locking, coming back here to
- * remove list elements, taking the irq_lock to do so.
+
+/* When epoll triggers we do not know why it did so
+ * we can also have different IRQs for read and write.
+ * This is why we keep a small irq_fd array for each fd -
+ * one entry per IRQ type
  */
-static struct irq_fd *active_fds = NULL;
-static struct irq_fd **last_irq_ptr = &active_fds;
 
-extern void free_irqs(void);
+struct irq_entry {
+	struct irq_entry *next;
+	int fd;
+	struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
+};
+
+static struct irq_entry *active_fds;
+
+static DEFINE_SPINLOCK(irq_lock);
+
+static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
+{
+/*
+ * irq->active guards against reentry
+ * irq->pending accumulates pending requests
+ * if pending is raised the irq_handler is re-run
+ * until pending is cleared
+ */
+	if (irq->active) {
+		irq->active = false;
+		do {
+			irq->pending = false;
+			do_IRQ(irq->irq, regs);
+		} while (irq->pending && (!irq->purge));
+		if (!irq->purge)
+			irq->active = true;
+	} else {
+		irq->pending = true;
+	}
+}
 
 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
-	struct irq_fd *irq_fd;
-	int n;
+	struct irq_entry *irq_entry;
+	struct irq_fd *irq;
+
+	int n, i, j;
 
 	while (1) {
-		n = os_waiting_for_events(active_fds);
+		/* This is now lockless - epoll keeps back-referencesto the irqs
+		 * which have trigger it so there is no need to walk the irq
+		 * list and lock it every time. We avoid locking by turning off
+		 * IO for a specific fd by executing os_del_epoll_fd(fd) before
+		 * we do any changes to the actual data structures
+		 */
+		n = os_waiting_for_events_epoll();
+
 		if (n <= 0) {
 			if (n == -EINTR)
 				continue;
-			else break;
+			else
+				break;
 		}
 
-		for (irq_fd = active_fds; irq_fd != NULL;
-		     irq_fd = irq_fd->next) {
-			if (irq_fd->current_events != 0) {
-				irq_fd->current_events = 0;
-				do_IRQ(irq_fd->irq, regs);
+		for (i = 0; i < n ; i++) {
+			/* Epoll back reference is the entry with 3 irq_fd
+			 * leaves - one for each irq type.
+			 */
+			irq_entry = (struct irq_entry *)
+				os_epoll_get_data_pointer(i);
+			for (j = 0; j < MAX_IRQ_TYPE ; j++) {
+				irq = irq_entry->irq_array[j];
+				if (irq == NULL)
+					continue;
+				if (os_epoll_triggered(i, irq->events) > 0)
+					irq_io_loop(irq, regs);
+				if (irq->purge) {
+					irq_entry->irq_array[j] = NULL;
+					kfree(irq);
+				}
 			}
 		}
 	}
+}
+
+static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
+{
+	int i;
+	int events = 0;
+	struct irq_fd *irq;
 
-	free_irqs();
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		irq = irq_entry->irq_array[i];
+		if (irq != NULL)
+			events = irq->events | events;
+	}
+	if (events > 0) {
+	/* os_add_epoll will call os_mod_epoll if this already exists */
+		return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
+	}
+	/* No events - delete */
+	return os_del_epoll_fd(irq_entry->fd);
 }
 
-static DEFINE_SPINLOCK(irq_lock);
+
 
 static int activate_fd(int irq, int fd, int type, void *dev_id)
 {
-	struct pollfd *tmp_pfd;
-	struct irq_fd *new_fd, *irq_fd;
+	struct irq_fd *new_fd;
+	struct irq_entry *irq_entry;
+	int i, err, events;
 	unsigned long flags;
-	int events, err, n;
 
 	err = os_set_fd_async(fd);
 	if (err < 0)
 		goto out;
 
-	err = -ENOMEM;
-	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
-	if (new_fd == NULL)
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
 
-	if (type == IRQ_READ)
-		events = UM_POLLIN | UM_POLLPRI;
-	else events = UM_POLLOUT;
-	*new_fd = ((struct irq_fd) { .next  		= NULL,
-				     .id 		= dev_id,
-				     .fd 		= fd,
-				     .type 		= type,
-				     .irq 		= irq,
-				     .events 		= events,
-				     .current_events 	= 0 } );
+	/* Check if we have an entry for this fd */
 
 	err = -EBUSY;
-	spin_lock_irqsave(&irq_lock, flags);
-	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
-		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
-			printk(KERN_ERR "Registering fd %d twice\n", fd);
-			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
-			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
-			       dev_id);
+	for (irq_entry = active_fds;
+		irq_entry != NULL; irq_entry = irq_entry->next) {
+		if (irq_entry->fd == fd)
+			break;
+	}
+
+	if (irq_entry == NULL) {
+		/* This needs to be atomic as it may be called from an
+		 * IRQ context.
+		 */
+		irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
+		if (irq_entry == NULL) {
+			printk(KERN_ERR
+				"Failed to allocate new IRQ entry\n");
 			goto out_unlock;
 		}
+		irq_entry->fd = fd;
+		for (i = 0; i < MAX_IRQ_TYPE; i++)
+			irq_entry->irq_array[i] = NULL;
+		irq_entry->next = active_fds;
+		active_fds = irq_entry;
 	}
 
-	if (type == IRQ_WRITE)
-		fd = -1;
-
-	tmp_pfd = NULL;
-	n = 0;
+	/* Check if we are trying to re-register an interrupt for a
+	 * particular fd
+	 */
 
-	while (1) {
-		n = os_create_pollfd(fd, events, tmp_pfd, n);
-		if (n == 0)
-			break;
+	if (irq_entry->irq_array[type] != NULL) {
+		printk(KERN_ERR
+			"Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
+			irq, fd, type, dev_id
+		);
+		goto out_unlock;
+	} else {
+		/* New entry for this fd */
+
+		err = -ENOMEM;
+		new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
+		if (new_fd == NULL)
+			goto out_unlock;
 
-		/*
-		 * n > 0
-		 * It means we couldn't put new pollfd to current pollfds
-		 * and tmp_fds is NULL or too small for new pollfds array.
-		 * Needed size is equal to n as minimum.
-		 *
-		 * Here we have to drop the lock in order to call
-		 * kmalloc, which might sleep.
-		 * If something else came in and changed the pollfds array
-		 * so we will not be able to put new pollfd struct to pollfds
-		 * then we free the buffer tmp_fds and try again.
+		events = os_event_mask(type);
+
+		*new_fd = ((struct irq_fd) {
+			.id		= dev_id,
+			.irq		= irq,
+			.type		= type,
+			.events		= events,
+			.active		= true,
+			.pending	= false,
+			.purge		= false
+		});
+		/* Turn off any IO on this fd - allows us to
+		 * avoid locking the IRQ loop
 		 */
-		spin_unlock_irqrestore(&irq_lock, flags);
-		kfree(tmp_pfd);
-
-		tmp_pfd = kmalloc(n, GFP_KERNEL);
-		if (tmp_pfd == NULL)
-			goto out_kfree;
-
-		spin_lock_irqsave(&irq_lock, flags);
+		os_del_epoll_fd(irq_entry->fd);
+		irq_entry->irq_array[type] = new_fd;
 	}
 
-	*last_irq_ptr = new_fd;
-	last_irq_ptr = &new_fd->next;
-
+	/* Turn back IO on with the correct (new) IO event mask */
+	assign_epoll_events_to_irq(irq_entry);
 	spin_unlock_irqrestore(&irq_lock, flags);
-
-	/*
-	 * This calls activate_fd, so it has to be outside the critical
-	 * section.
-	 */
-	maybe_sigio_broken(fd, (type == IRQ_READ));
+	maybe_sigio_broken(fd, (type != IRQ_NONE));
 
 	return 0;
-
- out_unlock:
+out_unlock:
 	spin_unlock_irqrestore(&irq_lock, flags);
- out_kfree:
-	kfree(new_fd);
- out:
+out:
 	return err;
 }
 
-static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
+/*
+ * Walk the IRQ list and dispose of any unused entries.
+ * Should be done under irq_lock.
+ */
+
+static void garbage_collect_irq_entries(void)
 {
-	unsigned long flags;
+	int i;
+	bool reap;
+	struct irq_entry *walk;
+	struct irq_entry *previous = NULL;
+	struct irq_entry *to_free;
 
-	spin_lock_irqsave(&irq_lock, flags);
-	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
-	spin_unlock_irqrestore(&irq_lock, flags);
+	if (active_fds == NULL)
+		return;
+	walk = active_fds;
+	while (walk != NULL) {
+		reap = true;
+		for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+			if (walk->irq_array[i] != NULL) {
+				reap = false;
+				break;
+			}
+		}
+		if (reap) {
+			if (previous == NULL)
+				active_fds = walk->next;
+			else
+				previous->next = walk->next;
+			to_free = walk;
+		} else {
+			to_free = NULL;
+		}
+		walk = walk->next;
+		if (to_free != NULL)
+			kfree(to_free);
+	}
 }
 
-struct irq_and_dev {
-	int irq;
-	void *dev;
-};
+/*
+ * Walk the IRQ list and get the descriptor for our FD
+ */
 
-static int same_irq_and_dev(struct irq_fd *irq, void *d)
+static struct irq_entry *get_irq_entry_by_fd(int fd)
 {
-	struct irq_and_dev *data = d;
+	struct irq_entry *walk = active_fds;
 
-	return ((irq->irq == data->irq) && (irq->id == data->dev));
+	while (walk != NULL) {
+		if (walk->fd == fd)
+			return walk;
+		walk = walk->next;
+	}
+	return NULL;
 }
 
-static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
-{
-	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
-							  .dev  = dev });
 
-	free_irq_by_cb(same_irq_and_dev, &data);
-}
+/*
+ * Walk the IRQ list and dispose of an entry for a specific
+ * device, fd and number. Note - if sharing an IRQ for read
+ * and writefor the same FD it will be disposed in either case.
+ * If this behaviour is undesirable use different IRQ ids.
+ */
 
-static int same_fd(struct irq_fd *irq, void *fd)
-{
-	return (irq->fd == *((int *)fd));
-}
+#define IGNORE_IRQ 1
+#define IGNORE_DEV (1<<1)
 
-void free_irq_by_fd(int fd)
+static void do_free_by_irq_and_dev(
+	struct irq_entry *irq_entry,
+	unsigned int irq,
+	void *dev,
+	int flags
+)
 {
-	free_irq_by_cb(same_fd, &fd);
+	int i;
+	struct irq_fd *to_free;
+
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		if (irq_entry->irq_array[i] != NULL) {
+			if (
+			((flags & IGNORE_IRQ) ||
+				(irq_entry->irq_array[i]->irq == irq)) &&
+			((flags & IGNORE_DEV) ||
+				(irq_entry->irq_array[i]->id == dev))
+			) {
+				/* Turn off any IO on this fd - allows us to
+				 * avoid locking the IRQ loop
+				 */
+				os_del_epoll_fd(irq_entry->fd);
+				to_free = irq_entry->irq_array[i];
+				irq_entry->irq_array[i] = NULL;
+				assign_epoll_events_to_irq(irq_entry);
+				if (to_free->active)
+					to_free->purge = true;
+				else
+					kfree(to_free);
+			}
+		}
+	}
 }
 
-/* Must be called with irq_lock held */
-static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
+void free_irq_by_fd(int fd)
 {
-	struct irq_fd *irq;
-	int i = 0;
-	int fdi;
+	struct irq_entry *to_free;
+	unsigned long flags;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		if ((irq->fd == fd) && (irq->irq == irqnum))
-			break;
-		i++;
-	}
-	if (irq == NULL) {
-		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
-		       fd);
-		goto out;
-	}
-	fdi = os_get_pollfd(i);
-	if ((fdi != -1) && (fdi != fd)) {
-		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
-		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
-		       fdi, fd);
-		irq = NULL;
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
 	}
-	*index_out = i;
- out:
-	return irq;
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
 }
 
-void reactivate_fd(int fd, int irqnum)
+static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irq,
+			dev,
+			0
+		);
+		to_free = to_free->next;
 	}
-	os_set_pollfd(i, irq->fd);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
+}
 
-	add_sigio_fd(fd);
+
+void reactivate_fd(int fd, int irqnum)
+{
+	/** NOP - we do auto-EOI now **/
 }
 
 void deactivate_fd(int fd, int irqnum)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
+	os_del_epoll_fd(fd);
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irqnum,
+			NULL,
+			IGNORE_DEV
+		);
 	}
-
-	os_set_pollfd(i, -1);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
-
 	ignore_sigio_fd(fd);
 }
 EXPORT_SYMBOL(deactivate_fd);
@@ -265,17 +385,28 @@ EXPORT_SYMBOL(deactivate_fd);
  */
 int deactivate_all_fds(void)
 {
-	struct irq_fd *irq;
-	int err;
+	unsigned long flags;
+	struct irq_entry *to_free;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		err = os_clear_fd_async(irq->fd);
-		if (err)
-			return err;
-	}
-	/* If there is a signal already queued, after unblocking ignore it */
+	spin_lock_irqsave(&irq_lock, flags);
+	/* Stop IO. The IRQ loop has no lock so this is our
+	 * only way of making sure we are safe to dispose
+	 * of all IRQ handlers
+	 */
 	os_set_ioignore();
-
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
+		to_free = to_free->next;
+	}
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
+	os_close_epoll_fd();
 	return 0;
 }
 
@@ -353,8 +484,11 @@ void __init init_IRQ(void)
 
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
+
 	for (i = 1; i < NR_IRQS; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
+	/* Initialize EPOLL Loop */
+	os_setup_epoll();
 }
 
 /*
diff --git a/arch/um/os-Linux/irq.c b/arch/um/os-Linux/irq.c
index b9afb74b79ad..365823010346 100644
--- a/arch/um/os-Linux/irq.c
+++ b/arch/um/os-Linux/irq.c
@@ -1,135 +1,147 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
 
 #include <stdlib.h>
 #include <errno.h>
-#include <poll.h>
+#include <sys/epoll.h>
 #include <signal.h>
 #include <string.h>
 #include <irq_user.h>
 #include <os.h>
 #include <um_malloc.h>
 
+/* Epoll support */
+
+static int epollfd = -1;
+
+#define MAX_EPOLL_EVENTS 64
+
+static struct epoll_event epoll_events[MAX_EPOLL_EVENTS];
+
+/* Helper to return an Epoll data pointer from an epoll event structure.
+ * We need to keep this one on the userspace side to keep includes separate
+ */
+
+void *os_epoll_get_data_pointer(int index)
+{
+	return epoll_events[index].data.ptr;
+}
+
+/* Helper to compare events versus the events in the epoll structure.
+ * Same as above - needs to be on the userspace side
+ */
+
+
+int os_epoll_triggered(int index, int events)
+{
+	return epoll_events[index].events & events;
+}
+/* Helper to set the event mask.
+ * The event mask is opaque to the kernel side, because it does not have
+ * access to the right includes/defines for EPOLL constants.
+ */
+
+int os_event_mask(int irq_type)
+{
+	if (irq_type == IRQ_READ)
+		return EPOLLIN | EPOLLPRI;
+	if (irq_type == IRQ_WRITE)
+		return EPOLLOUT;
+	return 0;
+}
+
 /*
- * Locked by irq_lock in arch/um/kernel/irq.c.  Changed by os_create_pollfd
- * and os_free_irq_by_cb, which are called under irq_lock.
+ * Initial Epoll Setup
  */
-static struct pollfd *pollfds = NULL;
-static int pollfds_num = 0;
-static int pollfds_size = 0;
+int os_setup_epoll(void)
+{
+	epollfd = epoll_create(MAX_EPOLL_EVENTS);
+	return epollfd;
+}
 
-int os_waiting_for_events(struct irq_fd *active_fds)
+/*
+ * Helper to run the actual epoll_wait
+ */
+int os_waiting_for_events_epoll(void)
 {
-	struct irq_fd *irq_fd;
-	int i, n, err;
+	int n, err;
 
-	n = poll(pollfds, pollfds_num, 0);
+	n = epoll_wait(epollfd,
+		(struct epoll_event *) &epoll_events, MAX_EPOLL_EVENTS, 0);
 	if (n < 0) {
 		err = -errno;
 		if (errno != EINTR)
-			printk(UM_KERN_ERR "os_waiting_for_events:"
-			       " poll returned %d, errno = %d\n", n, errno);
+			printk(
+				UM_KERN_ERR "os_waiting_for_events:"
+				" epoll returned %d, error = %s\n", n,
+				strerror(errno)
+			);
 		return err;
 	}
-
-	if (n == 0)
-		return 0;
-
-	irq_fd = active_fds;
-
-	for (i = 0; i < pollfds_num; i++) {
-		if (pollfds[i].revents != 0) {
-			irq_fd->current_events = pollfds[i].revents;
-			pollfds[i].fd = -1;
-		}
-		irq_fd = irq_fd->next;
-	}
 	return n;
 }
 
-int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds)
-{
-	if (pollfds_num == pollfds_size) {
-		if (size_tmpfds <= pollfds_size * sizeof(pollfds[0])) {
-			/* return min size needed for new pollfds area */
-			return (pollfds_size + 1) * sizeof(pollfds[0]);
-		}
-
-		if (pollfds != NULL) {
-			memcpy(tmp_pfd, pollfds,
-			       sizeof(pollfds[0]) * pollfds_size);
-			/* remove old pollfds */
-			kfree(pollfds);
-		}
-		pollfds = tmp_pfd;
-		pollfds_size++;
-	} else
-		kfree(tmp_pfd);	/* remove not used tmp_pfd */
-
-	pollfds[pollfds_num] = ((struct pollfd) { .fd		= fd,
-						  .events	= events,
-						  .revents	= 0 });
-	pollfds_num++;
-
-	return 0;
-}
 
-void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2)
+/*
+ * Helper to add a fd to epoll
+ */
+int os_add_epoll_fd(int events, int fd, void *data)
 {
-	struct irq_fd **prev;
-	int i = 0;
-
-	prev = &active_fds;
-	while (*prev != NULL) {
-		if ((*test)(*prev, arg)) {
-			struct irq_fd *old_fd = *prev;
-			if ((pollfds[i].fd != -1) &&
-			    (pollfds[i].fd != (*prev)->fd)) {
-				printk(UM_KERN_ERR "os_free_irq_by_cb - "
-				       "mismatch between active_fds and "
-				       "pollfds, fd %d vs %d\n",
-				       (*prev)->fd, pollfds[i].fd);
-				goto out;
-			}
-
-			pollfds_num--;
-
-			/*
-			 * This moves the *whole* array after pollfds[i]
-			 * (though it doesn't spot as such)!
-			 */
-			memmove(&pollfds[i], &pollfds[i + 1],
-			       (pollfds_num - i) * sizeof(pollfds[0]));
-			if (*last_irq_ptr2 == &old_fd->next)
-				*last_irq_ptr2 = prev;
-
-			*prev = (*prev)->next;
-			if (old_fd->type == IRQ_WRITE)
-				ignore_sigio_fd(old_fd->fd);
-			kfree(old_fd);
-			continue;
-		}
-		prev = &(*prev)->next;
-		i++;
-	}
- out:
-	return;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events | EPOLLET;
+	result = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
+	if ((result) && (errno == EEXIST))
+		result = os_mod_epoll_fd(events, fd, data);
+	if (result)
+		printk("epollctl add err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-int os_get_pollfd(int i)
+/*
+ * Helper to mod the fd event mask and/or data backreference
+ */
+int os_mod_epoll_fd(int events, int fd, void *data)
 {
-	return pollfds[i].fd;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events;
+	result = epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
+	if (result)
+		printk(UM_KERN_ERR
+			"epollctl mod err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-void os_set_pollfd(int i, int fd)
+/*
+ * Helper to delete the epoll fd
+ */
+int os_del_epoll_fd(int fd)
 {
-	pollfds[i].fd = fd;
+	struct epoll_event event;
+	int result;
+	/* This is quiet as we use this as IO ON/OFF - so it is often
+	 * invoked on a non-existent fd
+	 */
+	result = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
+	return result;
 }
 
 void os_set_ioignore(void)
 {
 	signal(SIGIO, SIG_IGN);
 }
+
+void os_close_epoll_fd(void)
+{
+	/* Needed so we do not leak an fd when rebooting */
+	os_close_file(epollfd);
+}
-- 
2.11.0

[uml-devel] PATCH v10

[<ant...@ko...>]

Follows a version of the patch after a style cleanup. Functionality
features and code have no material changes compared to previous version.

A.

Re: [uml-devel] [PATCH v9 2/2] High Performance UML Vector Network Driver

[Richard W. <ri...@si...>]

Anton,

Am Montag, 20. November 2017, 08:39:25 CET schrieb anton.ivanov@kot-
begemot.co.uk:
> +#define VECTOR_NUM_STATS	ARRAY_SIZE(ethtool_stats_keys)
> +
> +/* Used in the 4.4 OpenWRT backport */
> +
> +#if LINUX_VERSION_CODE <= KERNEL_VERSION(4, 7, 0)
> +static inline void netif_trans_update(struct net_device *dev)
> +{
> +	struct netdev_queue *txq = netdev_get_tx_queue(dev, 0);
> +
> +	if (txq->trans_start != jiffies)
> +		txq->trans_start = jiffies;
> +}
> +#endif

Didn't checkpatch.pl puke here?

Thanks,
//richard

-- 
sigma star gmbh - Eduard-Bodem-Gasse 6 - 6020 Innsbruck - Austria
ATU66964118 - FN 374287y

[uml-devel] [PATCH v9 1/2] Epoll based IRQ controller

[<ant...@ko...>]

From: Anton Ivanov <ant...@ca...>

1. Removes the need to walk the IRQ/Device list to determine
who triggered the IRQ.
2. Improves scalability (up to several times performance
improvement for cases with 10s of devices).
3. Improves UML baseline IO performance for one disk + one NIC
use case by up to 10%.
4. Introduces write poll triggered IRQs.
5. Prerequisite for introducing high performance mmesg family
of functions in network IO.
6. Fixes RNG shutdown which was leaking a file descriptor

Signed-off-by: Anton Ivanov <ant...@ca...>
---
 arch/um/drivers/chan_kern.c       |  53 +----
 arch/um/drivers/line.c            |   2 +-
 arch/um/drivers/random.c          |  11 +-
 arch/um/drivers/ubd_kern.c        |   4 +-
 arch/um/include/shared/irq_user.h |  12 +-
 arch/um/include/shared/os.h       |  17 +-
 arch/um/kernel/irq.c              | 460 ++++++++++++++++++++++++--------------
 arch/um/os-Linux/irq.c            | 202 +++++++++--------
 8 files changed, 444 insertions(+), 317 deletions(-)

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index acbe6c67afba..05588f9466c7 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -171,56 +171,19 @@ int enable_chan(struct line *line)
 	return err;
 }
 
-/* Items are added in IRQ context, when free_irq can't be called, and
- * removed in process context, when it can.
- * This handles interrupt sources which disappear, and which need to
- * be permanently disabled.  This is discovered in IRQ context, but
- * the freeing of the IRQ must be done later.
- */
-static DEFINE_SPINLOCK(irqs_to_free_lock);
-static LIST_HEAD(irqs_to_free);
-
-void free_irqs(void)
-{
-	struct chan *chan;
-	LIST_HEAD(list);
-	struct list_head *ele;
-	unsigned long flags;
-
-	spin_lock_irqsave(&irqs_to_free_lock, flags);
-	list_splice_init(&irqs_to_free, &list);
-	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-
-	list_for_each(ele, &list) {
-		chan = list_entry(ele, struct chan, free_list);
-
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
-}
-
 static void close_one_chan(struct chan *chan, int delay_free_irq)
 {
-	unsigned long flags;
-
 	if (!chan->opened)
 		return;
 
-	if (delay_free_irq) {
-		spin_lock_irqsave(&irqs_to_free_lock, flags);
-		list_add(&chan->free_list, &irqs_to_free);
-		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-	}
-	else {
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
+    /* we can safely call free now - it will be marked
+     *  as free and freed once the IRQ stopped processing
+     */
+	if (chan->input && chan->enabled)
+		um_free_irq(chan->line->driver->read_irq, chan);
+	if (chan->output && chan->enabled)
+		um_free_irq(chan->line->driver->write_irq, chan);
+	chan->enabled = 0;
 	if (chan->ops->close != NULL)
 		(*chan->ops->close)(chan->fd, chan->data);
 
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 366e57f5e8d6..8d80b27502e6 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -284,7 +284,7 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	if (err)
 		return err;
 	if (output)
-		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
+		err = um_request_irq(driver->write_irq, fd, IRQ_NONE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
 	return err;
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 37c51a6be690..778a0e52d5a5 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -13,6 +13,7 @@
 #include <linux/miscdevice.h>
 #include <linux/delay.h>
 #include <linux/uaccess.h>
+#include <init.h>
 #include <irq_kern.h>
 #include <os.h>
 
@@ -154,7 +155,14 @@ static int __init rng_init (void)
 /*
  * rng_cleanup - shutdown RNG module
  */
-static void __exit rng_cleanup (void)
+
+static void cleanup(void)
+{
+	free_irq_by_fd(random_fd);
+	os_close_file(random_fd);
+}
+
+static void __exit rng_cleanup(void)
 {
 	os_close_file(random_fd);
 	misc_deregister (&rng_miscdev);
@@ -162,6 +170,7 @@ static void __exit rng_cleanup (void)
 
 module_init (rng_init);
 module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
 
 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index b55fe9bf5d3e..d4e8c497ae86 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1587,11 +1587,11 @@ int io_thread(void *arg)
 
 		do {
 			res = os_write_file(kernel_fd, ((char *) io_req_buffer) + written, n);
-			if (res > 0) {
+			if (res >= 0) {
 				written += res;
 			} else {
 				if (res != -EAGAIN) {
-					printk("io_thread - read failed, fd = %d, "
+					printk("io_thread - write failed, fd = %d, "
 					       "err = %d\n", kernel_fd, -n);
 				}
 			}
diff --git a/arch/um/include/shared/irq_user.h b/arch/um/include/shared/irq_user.h
index df5633053957..a7a6120f19d5 100644
--- a/arch/um/include/shared/irq_user.h
+++ b/arch/um/include/shared/irq_user.h
@@ -7,6 +7,7 @@
 #define __IRQ_USER_H__
 
 #include <sysdep/ptrace.h>
+#include <stdbool.h>
 
 struct irq_fd {
 	struct irq_fd *next;
@@ -15,10 +16,17 @@ struct irq_fd {
 	int type;
 	int irq;
 	int events;
-	int current_events;
+	bool active;
+	bool pending;
+	bool purge;
 };
 
-enum { IRQ_READ, IRQ_WRITE };
+#define IRQ_READ  0
+#define IRQ_WRITE 1
+#define IRQ_NONE 2
+#define MAX_IRQ_TYPE (IRQ_NONE + 1)
+
+
 
 struct siginfo;
 extern void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 574e03fc7ba2..edbe6563d5c5 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -290,15 +290,16 @@ extern void halt_skas(void);
 extern void reboot_skas(void);
 
 /* irq.c */
-extern int os_waiting_for_events(struct irq_fd *active_fds);
-extern int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds);
-extern void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2);
-extern void os_free_irq_later(struct irq_fd *active_fds,
-		int irq, void *dev_id);
-extern int os_get_pollfd(int i);
-extern void os_set_pollfd(int i, int fd);
+extern int os_waiting_for_events_epoll(void);
+extern void *os_epoll_get_data_pointer(int index);
+extern int os_epoll_triggered(int index, int events);
+extern int os_event_mask(int irq_type);
+extern int os_setup_epoll(void);
+extern int os_add_epoll_fd(int events, int fd, void *data);
+extern int os_mod_epoll_fd(int events, int fd, void *data);
+extern int os_del_epoll_fd(int fd);
 extern void os_set_ioignore(void);
+extern void os_close_epoll_fd(void);
 
 /* sigio.c */
 extern int add_sigio_fd(int fd);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 23cb9350d47e..980148d56537 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -1,4 +1,6 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
@@ -16,243 +18,361 @@
 #include <as-layout.h>
 #include <kern_util.h>
 #include <os.h>
+#include <irq_user.h>
 
-/*
- * This list is accessed under irq_lock, except in sigio_handler,
- * where it is safe from being modified.  IRQ handlers won't change it -
- * if an IRQ source has vanished, it will be freed by free_irqs just
- * before returning from sigio_handler.  That will process a separate
- * list of irqs to free, with its own locking, coming back here to
- * remove list elements, taking the irq_lock to do so.
+
+/* When epoll triggers we do not know why it did so
+ * we can also have different IRQs for read and write.
+ * This is why we keep a small irq_fd array for each fd -
+ * one entry per IRQ type
  */
-static struct irq_fd *active_fds = NULL;
-static struct irq_fd **last_irq_ptr = &active_fds;
 
-extern void free_irqs(void);
+struct irq_entry {
+	struct irq_entry *next;
+	int fd;
+	struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
+};
+
+static struct irq_entry *active_fds;
+
+static DEFINE_SPINLOCK(irq_lock);
+
+static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
+{
+/*
+ * irq->active guards against reentry
+ * irq->pending accumulates pending requests
+ * if pending is raised the irq_handler is re-run
+ * until pending is cleared
+ */
+	if (irq->active) {
+		irq->active = false;
+		do {
+			irq->pending = false;
+			do_IRQ(irq->irq, regs);
+		} while (irq->pending && (!irq->purge));
+		if (!irq->purge)
+			irq->active = true;
+	} else {
+		irq->pending = true;
+	}
+}
 
 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
-	struct irq_fd *irq_fd;
-	int n;
+	struct irq_entry *irq_entry;
+	struct irq_fd *irq;
+
+	int n, i, j;
 
 	while (1) {
-		n = os_waiting_for_events(active_fds);
+		/* This is now lockless - epoll keeps back-referencesto the irqs
+		 * which have trigger it so there is no need to walk the irq
+		 * list and lock it every time. We avoid locking by turning off
+		 * IO for a specific fd by executing os_del_epoll_fd(fd) before
+		 * we do any changes to the actual data structures
+		 */
+		n = os_waiting_for_events_epoll();
+
 		if (n <= 0) {
 			if (n == -EINTR)
 				continue;
-			else break;
+			else
+				break;
 		}
 
-		for (irq_fd = active_fds; irq_fd != NULL;
-		     irq_fd = irq_fd->next) {
-			if (irq_fd->current_events != 0) {
-				irq_fd->current_events = 0;
-				do_IRQ(irq_fd->irq, regs);
+		for (i = 0; i < n ; i++) {
+			/* Epoll back reference is the entry with 3 irq_fd
+			 * leaves - one for each irq type.
+			 */
+			irq_entry = (struct irq_entry *)
+				os_epoll_get_data_pointer(i);
+			for (j = 0; j < MAX_IRQ_TYPE ; j++) {
+				irq = irq_entry->irq_array[j];
+				if (irq == NULL)
+					continue;
+				if (os_epoll_triggered(i, irq->events) > 0)
+					irq_io_loop(irq, regs);
+				if (irq->purge) {
+					irq_entry->irq_array[j] = NULL;
+					kfree(irq);
+				}
 			}
 		}
 	}
+}
+
+static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
+{
+	int i;
+	int events = 0;
+	struct irq_fd *irq;
 
-	free_irqs();
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		irq = irq_entry->irq_array[i];
+		if (irq != NULL)
+			events = irq->events | events;
+	}
+	if (events > 0) {
+	/* os_add_epoll will call os_mod_epoll if this already exists */
+		return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
+	}
+	/* No events - delete */
+	return os_del_epoll_fd(irq_entry->fd);
 }
 
-static DEFINE_SPINLOCK(irq_lock);
+
 
 static int activate_fd(int irq, int fd, int type, void *dev_id)
 {
-	struct pollfd *tmp_pfd;
-	struct irq_fd *new_fd, *irq_fd;
+	struct irq_fd *new_fd;
+	struct irq_entry *irq_entry;
+	int i, err, events;
 	unsigned long flags;
-	int events, err, n;
 
 	err = os_set_fd_async(fd);
 	if (err < 0)
 		goto out;
 
-	err = -ENOMEM;
-	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
-	if (new_fd == NULL)
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
 
-	if (type == IRQ_READ)
-		events = UM_POLLIN | UM_POLLPRI;
-	else events = UM_POLLOUT;
-	*new_fd = ((struct irq_fd) { .next  		= NULL,
-				     .id 		= dev_id,
-				     .fd 		= fd,
-				     .type 		= type,
-				     .irq 		= irq,
-				     .events 		= events,
-				     .current_events 	= 0 } );
+	/* Check if we have an entry for this fd */
 
 	err = -EBUSY;
-	spin_lock_irqsave(&irq_lock, flags);
-	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
-		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
-			printk(KERN_ERR "Registering fd %d twice\n", fd);
-			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
-			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
-			       dev_id);
+	for (irq_entry = active_fds;
+		irq_entry != NULL; irq_entry = irq_entry->next) {
+		if (irq_entry->fd == fd)
+			break;
+	}
+
+	if (irq_entry == NULL) {
+		/* This needs to be atomic as it may be called from an
+		 * IRQ context.
+		 */
+		irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
+		if (irq_entry == NULL) {
+			printk(KERN_ERR
+				"Failed to allocate new IRQ entry\n");
 			goto out_unlock;
 		}
+		irq_entry->fd = fd;
+		for (i = 0; i < MAX_IRQ_TYPE; i++)
+			irq_entry->irq_array[i] = NULL;
+		irq_entry->next = active_fds;
+		active_fds = irq_entry;
 	}
 
-	if (type == IRQ_WRITE)
-		fd = -1;
-
-	tmp_pfd = NULL;
-	n = 0;
+	/* Check if we are trying to re-register an interrupt for a
+	 * particular fd
+	 */
 
-	while (1) {
-		n = os_create_pollfd(fd, events, tmp_pfd, n);
-		if (n == 0)
-			break;
+	if (irq_entry->irq_array[type] != NULL) {
+		printk(KERN_ERR
+			"Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
+			irq, fd, type, dev_id
+		);
+		goto out_unlock;
+	} else {
+		/* New entry for this fd */
+
+		err = -ENOMEM;
+		new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
+		if (new_fd == NULL)
+			goto out_unlock;
 
-		/*
-		 * n > 0
-		 * It means we couldn't put new pollfd to current pollfds
-		 * and tmp_fds is NULL or too small for new pollfds array.
-		 * Needed size is equal to n as minimum.
-		 *
-		 * Here we have to drop the lock in order to call
-		 * kmalloc, which might sleep.
-		 * If something else came in and changed the pollfds array
-		 * so we will not be able to put new pollfd struct to pollfds
-		 * then we free the buffer tmp_fds and try again.
+		events = os_event_mask(type);
+
+		*new_fd = ((struct irq_fd) {
+			.id		= dev_id,
+			.irq		= irq,
+			.type		= type,
+			.events		= events,
+			.active		= true,
+			.pending	= false,
+			.purge		= false
+		});
+		/* Turn off any IO on this fd - allows us to
+		 * avoid locking the IRQ loop
 		 */
-		spin_unlock_irqrestore(&irq_lock, flags);
-		kfree(tmp_pfd);
-
-		tmp_pfd = kmalloc(n, GFP_KERNEL);
-		if (tmp_pfd == NULL)
-			goto out_kfree;
-
-		spin_lock_irqsave(&irq_lock, flags);
+		os_del_epoll_fd(irq_entry->fd);
+		irq_entry->irq_array[type] = new_fd;
 	}
 
-	*last_irq_ptr = new_fd;
-	last_irq_ptr = &new_fd->next;
-
+	/* Turn back IO on with the correct (new) IO event mask */
+	assign_epoll_events_to_irq(irq_entry);
 	spin_unlock_irqrestore(&irq_lock, flags);
-
-	/*
-	 * This calls activate_fd, so it has to be outside the critical
-	 * section.
-	 */
-	maybe_sigio_broken(fd, (type == IRQ_READ));
+	maybe_sigio_broken(fd, (type != IRQ_NONE));
 
 	return 0;
-
- out_unlock:
+out_unlock:
 	spin_unlock_irqrestore(&irq_lock, flags);
- out_kfree:
-	kfree(new_fd);
- out:
+out:
 	return err;
 }
 
-static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
+/*
+ * Walk the IRQ list and dispose of any unused entries.
+ * Should be done under irq_lock.
+ */
+
+static void garbage_collect_irq_entries(void)
 {
-	unsigned long flags;
+	int i;
+	bool reap;
+	struct irq_entry *walk;
+	struct irq_entry *previous = NULL;
+	struct irq_entry *to_free;
 
-	spin_lock_irqsave(&irq_lock, flags);
-	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
-	spin_unlock_irqrestore(&irq_lock, flags);
+	if (active_fds == NULL)
+		return;
+	walk = active_fds;
+	while (walk != NULL) {
+		reap = true;
+		for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+			if (walk->irq_array[i] != NULL) {
+				reap = false;
+				break;
+			}
+		}
+		if (reap) {
+			if (previous == NULL)
+				active_fds = walk->next;
+			else
+				previous->next = walk->next;
+			to_free = walk;
+		} else {
+			to_free = NULL;
+		}
+		walk = walk->next;
+		if (to_free != NULL)
+			kfree(to_free);
+	}
 }
 
-struct irq_and_dev {
-	int irq;
-	void *dev;
-};
+/*
+ * Walk the IRQ list and get the descriptor for our FD
+ */
 
-static int same_irq_and_dev(struct irq_fd *irq, void *d)
+static struct irq_entry *get_irq_entry_by_fd(int fd)
 {
-	struct irq_and_dev *data = d;
+	struct irq_entry *walk = active_fds;
 
-	return ((irq->irq == data->irq) && (irq->id == data->dev));
+	while (walk != NULL) {
+		if (walk->fd == fd)
+			return walk;
+		walk = walk->next;
+	}
+	return NULL;
 }
 
-static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
-{
-	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
-							  .dev  = dev });
 
-	free_irq_by_cb(same_irq_and_dev, &data);
-}
+/*
+ * Walk the IRQ list and dispose of an entry for a specific
+ * device, fd and number. Note - if sharing an IRQ for read
+ * and writefor the same FD it will be disposed in either case.
+ * If this behaviour is undesirable use different IRQ ids.
+ */
 
-static int same_fd(struct irq_fd *irq, void *fd)
-{
-	return (irq->fd == *((int *)fd));
-}
+#define IGNORE_IRQ 1
+#define IGNORE_DEV (1<<1)
 
-void free_irq_by_fd(int fd)
+static void do_free_by_irq_and_dev(
+	struct irq_entry *irq_entry,
+	unsigned int irq,
+	void *dev,
+	int flags
+)
 {
-	free_irq_by_cb(same_fd, &fd);
+	int i;
+	struct irq_fd *to_free;
+
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		if (irq_entry->irq_array[i] != NULL) {
+			if (
+			((flags & IGNORE_IRQ) ||
+				(irq_entry->irq_array[i]->irq == irq)) &&
+			((flags & IGNORE_DEV) ||
+				(irq_entry->irq_array[i]->id == dev))
+			) {
+				/* Turn off any IO on this fd - allows us to
+				 * avoid locking the IRQ loop
+				 */
+				os_del_epoll_fd(irq_entry->fd);
+				to_free = irq_entry->irq_array[i];
+				irq_entry->irq_array[i] = NULL;
+				assign_epoll_events_to_irq(irq_entry);
+				if (to_free->active)
+					to_free->purge = true;
+				else
+					kfree(to_free);
+			}
+		}
+	}
 }
 
-/* Must be called with irq_lock held */
-static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
+void free_irq_by_fd(int fd)
 {
-	struct irq_fd *irq;
-	int i = 0;
-	int fdi;
+	struct irq_entry *to_free;
+	unsigned long flags;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		if ((irq->fd == fd) && (irq->irq == irqnum))
-			break;
-		i++;
-	}
-	if (irq == NULL) {
-		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
-		       fd);
-		goto out;
-	}
-	fdi = os_get_pollfd(i);
-	if ((fdi != -1) && (fdi != fd)) {
-		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
-		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
-		       fdi, fd);
-		irq = NULL;
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
 	}
-	*index_out = i;
- out:
-	return irq;
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
 }
 
-void reactivate_fd(int fd, int irqnum)
+static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irq,
+			dev,
+			0
+		);
+		to_free = to_free->next;
 	}
-	os_set_pollfd(i, irq->fd);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
+}
 
-	add_sigio_fd(fd);
+
+void reactivate_fd(int fd, int irqnum)
+{
+	/** NOP - we do auto-EOI now **/
 }
 
 void deactivate_fd(int fd, int irqnum)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
+	os_del_epoll_fd(fd);
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irqnum,
+			NULL,
+			IGNORE_DEV
+		);
 	}
-
-	os_set_pollfd(i, -1);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
-
 	ignore_sigio_fd(fd);
 }
 EXPORT_SYMBOL(deactivate_fd);
@@ -265,17 +385,28 @@ EXPORT_SYMBOL(deactivate_fd);
  */
 int deactivate_all_fds(void)
 {
-	struct irq_fd *irq;
-	int err;
+	unsigned long flags;
+	struct irq_entry *to_free;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		err = os_clear_fd_async(irq->fd);
-		if (err)
-			return err;
-	}
-	/* If there is a signal already queued, after unblocking ignore it */
+	spin_lock_irqsave(&irq_lock, flags);
+	/* Stop IO. The IRQ loop has no lock so this is our
+	 * only way of making sure we are safe to dispose
+	 * of all IRQ handlers
+	 */
 	os_set_ioignore();
-
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
+		to_free = to_free->next;
+	}
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
+	os_close_epoll_fd();
 	return 0;
 }
 
@@ -353,8 +484,11 @@ void __init init_IRQ(void)
 
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
+
 	for (i = 1; i < NR_IRQS; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
+	/* Initialize EPOLL Loop */
+	os_setup_epoll();
 }
 
 /*
diff --git a/arch/um/os-Linux/irq.c b/arch/um/os-Linux/irq.c
index b9afb74b79ad..365823010346 100644
--- a/arch/um/os-Linux/irq.c
+++ b/arch/um/os-Linux/irq.c
@@ -1,135 +1,147 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
 
 #include <stdlib.h>
 #include <errno.h>
-#include <poll.h>
+#include <sys/epoll.h>
 #include <signal.h>
 #include <string.h>
 #include <irq_user.h>
 #include <os.h>
 #include <um_malloc.h>
 
+/* Epoll support */
+
+static int epollfd = -1;
+
+#define MAX_EPOLL_EVENTS 64
+
+static struct epoll_event epoll_events[MAX_EPOLL_EVENTS];
+
+/* Helper to return an Epoll data pointer from an epoll event structure.
+ * We need to keep this one on the userspace side to keep includes separate
+ */
+
+void *os_epoll_get_data_pointer(int index)
+{
+	return epoll_events[index].data.ptr;
+}
+
+/* Helper to compare events versus the events in the epoll structure.
+ * Same as above - needs to be on the userspace side
+ */
+
+
+int os_epoll_triggered(int index, int events)
+{
+	return epoll_events[index].events & events;
+}
+/* Helper to set the event mask.
+ * The event mask is opaque to the kernel side, because it does not have
+ * access to the right includes/defines for EPOLL constants.
+ */
+
+int os_event_mask(int irq_type)
+{
+	if (irq_type == IRQ_READ)
+		return EPOLLIN | EPOLLPRI;
+	if (irq_type == IRQ_WRITE)
+		return EPOLLOUT;
+	return 0;
+}
+
 /*
- * Locked by irq_lock in arch/um/kernel/irq.c.  Changed by os_create_pollfd
- * and os_free_irq_by_cb, which are called under irq_lock.
+ * Initial Epoll Setup
  */
-static struct pollfd *pollfds = NULL;
-static int pollfds_num = 0;
-static int pollfds_size = 0;
+int os_setup_epoll(void)
+{
+	epollfd = epoll_create(MAX_EPOLL_EVENTS);
+	return epollfd;
+}
 
-int os_waiting_for_events(struct irq_fd *active_fds)
+/*
+ * Helper to run the actual epoll_wait
+ */
+int os_waiting_for_events_epoll(void)
 {
-	struct irq_fd *irq_fd;
-	int i, n, err;
+	int n, err;
 
-	n = poll(pollfds, pollfds_num, 0);
+	n = epoll_wait(epollfd,
+		(struct epoll_event *) &epoll_events, MAX_EPOLL_EVENTS, 0);
 	if (n < 0) {
 		err = -errno;
 		if (errno != EINTR)
-			printk(UM_KERN_ERR "os_waiting_for_events:"
-			       " poll returned %d, errno = %d\n", n, errno);
+			printk(
+				UM_KERN_ERR "os_waiting_for_events:"
+				" epoll returned %d, error = %s\n", n,
+				strerror(errno)
+			);
 		return err;
 	}
-
-	if (n == 0)
-		return 0;
-
-	irq_fd = active_fds;
-
-	for (i = 0; i < pollfds_num; i++) {
-		if (pollfds[i].revents != 0) {
-			irq_fd->current_events = pollfds[i].revents;
-			pollfds[i].fd = -1;
-		}
-		irq_fd = irq_fd->next;
-	}
 	return n;
 }
 
-int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds)
-{
-	if (pollfds_num == pollfds_size) {
-		if (size_tmpfds <= pollfds_size * sizeof(pollfds[0])) {
-			/* return min size needed for new pollfds area */
-			return (pollfds_size + 1) * sizeof(pollfds[0]);
-		}
-
-		if (pollfds != NULL) {
-			memcpy(tmp_pfd, pollfds,
-			       sizeof(pollfds[0]) * pollfds_size);
-			/* remove old pollfds */
-			kfree(pollfds);
-		}
-		pollfds = tmp_pfd;
-		pollfds_size++;
-	} else
-		kfree(tmp_pfd);	/* remove not used tmp_pfd */
-
-	pollfds[pollfds_num] = ((struct pollfd) { .fd		= fd,
-						  .events	= events,
-						  .revents	= 0 });
-	pollfds_num++;
-
-	return 0;
-}
 
-void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2)
+/*
+ * Helper to add a fd to epoll
+ */
+int os_add_epoll_fd(int events, int fd, void *data)
 {
-	struct irq_fd **prev;
-	int i = 0;
-
-	prev = &active_fds;
-	while (*prev != NULL) {
-		if ((*test)(*prev, arg)) {
-			struct irq_fd *old_fd = *prev;
-			if ((pollfds[i].fd != -1) &&
-			    (pollfds[i].fd != (*prev)->fd)) {
-				printk(UM_KERN_ERR "os_free_irq_by_cb - "
-				       "mismatch between active_fds and "
-				       "pollfds, fd %d vs %d\n",
-				       (*prev)->fd, pollfds[i].fd);
-				goto out;
-			}
-
-			pollfds_num--;
-
-			/*
-			 * This moves the *whole* array after pollfds[i]
-			 * (though it doesn't spot as such)!
-			 */
-			memmove(&pollfds[i], &pollfds[i + 1],
-			       (pollfds_num - i) * sizeof(pollfds[0]));
-			if (*last_irq_ptr2 == &old_fd->next)
-				*last_irq_ptr2 = prev;
-
-			*prev = (*prev)->next;
-			if (old_fd->type == IRQ_WRITE)
-				ignore_sigio_fd(old_fd->fd);
-			kfree(old_fd);
-			continue;
-		}
-		prev = &(*prev)->next;
-		i++;
-	}
- out:
-	return;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events | EPOLLET;
+	result = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
+	if ((result) && (errno == EEXIST))
+		result = os_mod_epoll_fd(events, fd, data);
+	if (result)
+		printk("epollctl add err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-int os_get_pollfd(int i)
+/*
+ * Helper to mod the fd event mask and/or data backreference
+ */
+int os_mod_epoll_fd(int events, int fd, void *data)
 {
-	return pollfds[i].fd;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events;
+	result = epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
+	if (result)
+		printk(UM_KERN_ERR
+			"epollctl mod err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-void os_set_pollfd(int i, int fd)
+/*
+ * Helper to delete the epoll fd
+ */
+int os_del_epoll_fd(int fd)
 {
-	pollfds[i].fd = fd;
+	struct epoll_event event;
+	int result;
+	/* This is quiet as we use this as IO ON/OFF - so it is often
+	 * invoked on a non-existent fd
+	 */
+	result = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
+	return result;
 }
 
 void os_set_ioignore(void)
 {
 	signal(SIGIO, SIG_IGN);
 }
+
+void os_close_epoll_fd(void)
+{
+	/* Needed so we do not leak an fd when rebooting */
+	os_close_file(epollfd);
+}
-- 
2.11.0

[uml-devel] PATCH v9

[<ant...@ko...>]

This is (hopefully) the final version of the epoll + vector IO
patch. It incorporates the TSO fixes for raw and minor errata
for POLL_CONTROLLER.

A.

Re: [uml-devel] [PATCH] um: use POSIX ucontext_t instead of struct ucontext

[Richard W. <ri...@no...>]

Am Mittwoch, 15. November 2017, 12:04:16 CET schrieb Krzysztof Mazur:
> On Wed, Nov 15, 2017 at 11:19:41AM +0100, Richard Weinberger wrote:
> > Am Mittwoch, 15. November 2017, 11:12:39 CET schrieb Krzysztof Mazur:
> > > glibc 2.26 removed the 'struct ucontext' to "improve" POSIX compliance
> > > and break programs, including User Mode Linux. Fix User Mode Linux
> > > by using POSIX ucontext_t.
> > > 
> > > This fixes:
> > > 
> > > arch/um/os-Linux/signal.c: In function 'hard_handler':
> > > arch/um/os-Linux/signal.c:163:22: error: dereferencing pointer to
> > > incomplete type 'struct ucontext' mcontext_t *mc = &uc->uc_mcontext;
> > > arch/x86/um/stub_segv.c: In function 'stub_segv_handler':
> > > arch/x86/um/stub_segv.c:16:13: error: dereferencing pointer to
> > > incomplete
> > > type 'struct ucontext' &uc->uc_mcontext);
> > 
> > Do all older glibcs have ucontext_t?
> > Otherwise this patch will break other stuff.
> 
> Yes, ucontext_t typedef was always available. They changed:
> 
> typedef struct ucontext { ... } ucontex_t;
> 
> to
> 
> typedef struct ucontext_t { ... } ucontex_t;
> 
> https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.27struct_ucontext
> .27

Okay, then we can mark your patch as stable and hope for the best. ;-)

Thanks,
//richard

Re: [uml-devel] [PATCH] um: use POSIX ucontext_t instead of struct ucontext

[Richard W. <ri...@no...>]

Am Mittwoch, 15. November 2017, 11:12:39 CET schrieb Krzysztof Mazur:
> glibc 2.26 removed the 'struct ucontext' to "improve" POSIX compliance
> and break programs, including User Mode Linux. Fix User Mode Linux
> by using POSIX ucontext_t.
> 
> This fixes:
> 
> arch/um/os-Linux/signal.c: In function 'hard_handler':
> arch/um/os-Linux/signal.c:163:22: error: dereferencing pointer to incomplete
> type 'struct ucontext' mcontext_t *mc = &uc->uc_mcontext;
> arch/x86/um/stub_segv.c: In function 'stub_segv_handler':
> arch/x86/um/stub_segv.c:16:13: error: dereferencing pointer to incomplete
> type 'struct ucontext' &uc->uc_mcontext);

Do all older glibcs have ucontext_t?
Otherwise this patch will break other stuff.

Thanks,
//richard 

[uml-devel] [PATCH] um/time: use timespec64 for persistent clock

[Arnd B. <ar...@ar...>]

This read_persistent_clock() implementation is the only remaining
caller of set_normalized_timespec(). Using read_persistent_clock64()
and set_normalized_timespec64() instead lets us remove the deprecated
interface in the future and helps make 32-bit arch/um get closer to
working beyond 2038.

Signed-off-by: Arnd Bergmann <ar...@ar...>
---
 arch/um/kernel/time.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 7f69d17de354..052de4c8acb2 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -121,12 +121,12 @@ static void __init um_timer_setup(void)
 	clockevents_register_device(&timer_clockevent);
 }
 
-void read_persistent_clock(struct timespec *ts)
+void read_persistent_clock64(struct timespec64 *ts)
 {
 	long long nsecs = os_persistent_clock_emulation();
 
-	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
-				nsecs % NSEC_PER_SEC);
+	set_normalized_timespec64(ts, nsecs / NSEC_PER_SEC,
+				  nsecs % NSEC_PER_SEC);
 }
 
 void __init time_init(void)
-- 
2.9.0

Re: [uml-devel] [PATCH] um: Use common error handling code in port_listen_fd()

[Joe P. <jo...@pe...>]

On Fri, 2017-10-20 at 19:29 +0200, SF Markus Elfring wrote:
> arch/um/drivers/port_user.c

If you are going to use multiple labels,
it'd be nicer to rename out: too.

[uml-devel] [PATCH] um: Restore symbol versions for __memcpy and memcpy

[Geert U. <ge...@li...>]

If CONFIG_MODVERSIONS=y:

    WARNING: EXPORT symbol "__memcpy" [vmlinux] version generation failed, symbol will not be versioned.
    WARNING: EXPORT symbol "memcpy" [vmlinux] version generation failed, symbol will not be versioned.

Add <asm/asm-prototypes.h>, including the generic version, so that
genksyms knows the types of these symbols and can generate CRCs for
them.

Signed-off-by: Geert Uytterhoeven <ge...@li...>
---
 arch/um/include/asm/asm-prototypes.h | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 arch/um/include/asm/asm-prototypes.h

diff --git a/arch/um/include/asm/asm-prototypes.h b/arch/um/include/asm/asm-prototypes.h
new file mode 100644
index 0000000000000000..5898a26daa0dd4fa
--- /dev/null
+++ b/arch/um/include/asm/asm-prototypes.h
@@ -0,0 +1 @@
+#include <asm-generic/asm-prototypes.h>
-- 
2.7.4

Re: [uml-devel] [PATCH] um: Fix kcov crash before kernel is started.

[Anton I. <ant...@ko...>]

On 14/10/17 09:05, Richard Weinberger wrote:
> Am Samstag, 14. Oktober 2017, 00:00:25 CEST schrieb Thomas Meyer:
>> UMLs current_thread_info() unconditionally assumes that the top of the stack
>> contains the thread_info structure.
>> Prevent kcov from using invalid curent_thread_info() data by disable
>> instrumentation of early startup code.
>>
>> Signed-off-by: Thomas Meyer <th...@m3...>
>> ---
>>  arch/um/kernel/skas/Makefile | 2 ++
>>  lib/Makefile                 | 4 ++++
>>  2 files changed, 6 insertions(+)
>>
>> diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile
>> index 0b76d8869c94..df3aedb974a2 100644
>> --- a/arch/um/kernel/skas/Makefile
>> +++ b/arch/um/kernel/skas/Makefile
>> @@ -3,6 +3,8 @@
>>  # Licensed under the GPL
>>  #
>>
>> +KCOV_INSTRUMENT                := n
> So, you disable kconv for the whole SKAS code?
> That's a bit broad. ;-\

It is a part of UML which most of us approach with a distinct feeling of
dread. At least I do.

It may be worth it to do that in first instance and then try to narrow
down sections which can have it later on :)

A.

>
>>  obj-y := clone.o mmu.o process.o syscall.o uaccess.o
>>
>>  # clone.o is in the stub, so it can't be built with profiling
>> diff --git a/lib/Makefile b/lib/Makefile
>> index dafa79613fb4..18319ad5daab 100644
>> --- a/lib/Makefile
>> +++ b/lib/Makefile
>> @@ -16,6 +16,10 @@ KCOV_INSTRUMENT_list_debug.o := n
>>  KCOV_INSTRUMENT_debugobjects.o := n
>>  KCOV_INSTRUMENT_dynamic_debug.o := n
>>
>> +ifdef CONFIG_UML
>> +KCOV_INSTRUMENT_cmdline.o := n
>> +endif
>> +
> huh? Why do we need an exception for UML here?
>
> Thanks,
> //richard
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> User-mode-linux-devel mailing list
> Use...@li...
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
>

Re: [uml-devel] [PATCH] um: Fix kcov crash before kernel is started.

[Richard W. <ri...@no...>]

Am Samstag, 14. Oktober 2017, 00:00:25 CEST schrieb Thomas Meyer:
> UMLs current_thread_info() unconditionally assumes that the top of the stack
> contains the thread_info structure.
> Prevent kcov from using invalid curent_thread_info() data by disable
> instrumentation of early startup code.
> 
> Signed-off-by: Thomas Meyer <th...@m3...>
> ---
>  arch/um/kernel/skas/Makefile | 2 ++
>  lib/Makefile                 | 4 ++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile
> index 0b76d8869c94..df3aedb974a2 100644
> --- a/arch/um/kernel/skas/Makefile
> +++ b/arch/um/kernel/skas/Makefile
> @@ -3,6 +3,8 @@
>  # Licensed under the GPL
>  #
> 
> +KCOV_INSTRUMENT                := n

So, you disable kconv for the whole SKAS code?
That's a bit broad. ;-\

>  obj-y := clone.o mmu.o process.o syscall.o uaccess.o
> 
>  # clone.o is in the stub, so it can't be built with profiling
> diff --git a/lib/Makefile b/lib/Makefile
> index dafa79613fb4..18319ad5daab 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -16,6 +16,10 @@ KCOV_INSTRUMENT_list_debug.o := n
>  KCOV_INSTRUMENT_debugobjects.o := n
>  KCOV_INSTRUMENT_dynamic_debug.o := n
> 
> +ifdef CONFIG_UML
> +KCOV_INSTRUMENT_cmdline.o := n
> +endif
> +

huh? Why do we need an exception for UML here?

Thanks,
//richard

Re: [uml-devel] BUG:af_packet fails to TX TSO frames

[Anton I. <ant...@ko...>]

Also confirmed using my UML patchset. This is inside the UML guest.

root@blinky:~# iperf -c 192.168.98.1
------------------------------------------------------------
Client connecting to 192.168.98.1, TCP port 5001
TCP window size:  414 KByte (default)
------------------------------------------------------------
[  3] local 192.168.98.146 port 36744 connected with 192.168.98.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  4.52 GBytes  3.89 Gbits/sec

This is GSO on a raw socket Virtual NIC to host. Normal speed without 
GSO on same machine is ~ 500.

So for the time being I can turn off TSO for anything but v4 in the User 
Mode Linux patchset (declare the guest NIC as TSOV4 capable only) and 
enable it once the host kernel is fixed. Alternatively, there is the 
rather ugly approach of using multiple FDs - one for v4, one for v6, one 
for...

A.

On 10/12/17 16:44, Anton Ivanov wrote:
> Found it.
>
> Two bugs canceling each other.
> The bind sequence in:  psock_txring_vnet.c is wrong.
>
> It does the following addr.sll_protocol =    htons(ETH_P_IP);
> before calling bind.
>
> If you set addr.sll_protocol to ETH_P_ALL where it should have been in 
> the first place the test program blows up with -ENOBUFS
>
> I think what is happening is that this value is taken into account 
> when looking at "what should I use to segment it with" in 
> skb_mac_gso_segment which is invoked at the end of the verification 
> chain which starts in packet_direct_xmit in af_packet.c
>
> I have not tried the other test cases like setting it to ETH_P_IP and 
> giving it IPv6 traffic or the opposite, but my guess is that these 
> will fail too if they need GSO to be applied.
>
> A.
>
> On 10/12/17 15:12, Anton Ivanov wrote:
>>
>>
>> On 10/12/17 14:39, Willem de Bruijn wrote:
>>>> If I produce a real vnet frame out of a live kernel frame using
>>>> virtio_net_hdr_from_skb() and try to send it it fails on the check in
>>>> af_packet, while succeeding for tap. If I remove the af_packet 
>>>> check the
>>>> frame is accepted by the hardware too.
>>>>
>>>> If I produce it a synthetic frame + vnet header using the test 
>>>> program - it
>>>> works. Go figure.
>>> Besides looking at the raw frame bytes, also compare the setup
>>> of virtio_net_header, as well as the tcp checksum field. The stack
>>> expects the pseudo header to have already been calculated.
>>
>> I am feeding it a skb which is coming up in the tx routine of a User 
>> Mode Linux device which is marked as NETIF_F_HW_CSUM and SG - that 
>> results in a skb with csum-ed headers, body set up for CSUM_PARTIAL 
>> and multiple fragments (always at least 1 more frag besides the TCP 
>> head).
>>
>> That has everything in order as expected by virtio_net_hdr_from_skb 
>> and this is what I use to generate the vnet header. It works 
>> correctly for csum and GRO with af_packet and it works correctly for 
>> everything using a tap device. It fails only on GSO + af_packet TX.
>>
>> What I am doing is the same thing virtio_net does - it just takes the 
>> output of virtio_net_hdr_from_skb and does nothing more. There should 
>> be no need to do anything more :(
>>
>> It should just work.
>>
>> Unless there is a gremlin somewhere in the machinery and that gremlin 
>> needs some light to be flushed out.
>>>
>>>> I am going to continue digging into it.
>>>>
>>>> At the very least I now have a positive test case which uses the same
>>>> semantics as my code so I have something to compare to.
>>> Glad to hear that the test is helpful. I wrote it because I
>>> have run into these exact same issues in the past.
>>
>> It is. I have changes ready for it so it also supports vector IO, 
>> need to finish fighting with it.
>>
>> A.
>>
>>>
>>
>

[uml-devel] Fwd: Re: BUG:af_packet fails to TX TSO frames

[Anton I. <ant...@ko...>]

And that is the culprit of why GSO does not work with raw sockets.

There can be no workaround unfortunately, this simply will need to be
enabled in the driver once the kernel is fixed.

It should work for older kernels prior to the fix in comit104ba78c9880 too.

So from that perspective there is nothing that can be done to the vector
io drivers - the code is correct, it is the host kernel side which is
broken :(

A.

-------- Forwarded Message --------
Subject: 	Re: BUG:af_packet fails to TX TSO frames
Date: 	Wed, 11 Oct 2017 20:39:57 +0100
From: 	Anton Ivanov <ant...@ko...>
To: 	Willem de Bruijn <wil...@gm...>
CC: 	Anton Ivanov <ant...@ca...>, Network Development
<ne...@vg...>, David Miller <da...@da...>



On 11/10/17 19:57, Willem de Bruijn wrote:
> On Wed, Oct 11, 2017 at 2:39 PM, Anton Ivanov
> <ant...@ko...> wrote:
>> The check as now insists that the actual driver supports GSO_ROBUST, because
>> we have marked the skb dodgy.
>>
>> The specific bit which does this check is in net_gso_ok()
>>
>> Now, lets's see how many Ethernet drivers set GSO_ROBUST.
>>
>> find drivers/net/ethernet -type f -name "*.[c,h]" -exec grep -H GSO_ROBUST
>> {} \;
>>
>> That returns nothing in 4.x
>>
>> IMHO - af_packet allocates the skb, does all checks (and extra may be added)
>> on the gso, why is this set dodgy in the first place?
> It is set when the header has to be validated.
>
> The segmentation logic will validate and fixup gso_segs. See for
> instance tcp_gso_segment:
>
>         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
>                 /* Packet is from an untrusted source, reset gso_segs. */
>
>                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
>
>                 segs = NULL;
>                 goto out;
>         }
>
> If the device would have the robust bit set and otherwise supports the
> required features, fix up gso_segs and pass the large packet to the
> device.
>
> Else it continues to the software gso path.
>
> Large packets generated with psock_txring_vnet.c pass this test. I

That test is indeed a different path - this goes via the tpacket_snd
which allocs via sock_alloc_send_skb. That results in a non-fragged skb
as it calls pskb after that with data_len = 0 asking for a contiguous one.

My stuff is using sendmmsg which ends up via packet_snd which allocs
via  sock_alloc_send_pskb which is invoked in a way which always creates
2 segments - one for the linear section and one for the rest (and more
if needed). It is faster than tpacket by the way (several times).

As a comparison tap and other virtual drivers use sock_alloc_send_pskb
with non-zero data length which results in multiple frags. The code in
packet_snd is in fact identical with tap (+/- some cosmetic differences).

That is the difference between the tests and that is why your test works
and mine fails.

Now, alloc-ing a 64k contiguous skb every time IMHO is wrong.

So the logic in the xmit check at present works only because it is given
only a very corner case for a GSO frame and tested versus it. It should
work with the generic case which is what comes out of
sock_alloc_send_pskb (same as in tap).

A.



> suspect that there is a subtle difference in the virtio_net_hdr fields
> that that generates vs. your program.
>

[uml-devel] [PATCH 1/2] Epoll based IRQ controller

[<ant...@ko...>]

From: Anton Ivanov <ant...@ca...>

1. Removes the need to walk the IRQ/Device list to determine
who triggered the IRQ.
2. Improves scalability (up to several times performance
improvement for cases with 10s of devices).
3. Improves UML baseline IO performance for one disk + one NIC
use case by up to 10%.
4. Introduces write poll triggered IRQs.
5. Prerequisite for introducing high performance mmesg family
of functions in network IO.
6. Fixes RNG shutdown which was leaking a file descriptor

Signed-off-by: Anton Ivanov <ant...@ca...>
---
 arch/um/drivers/chan_kern.c       |  53 +----
 arch/um/drivers/line.c            |   2 +-
 arch/um/drivers/random.c          |  11 +-
 arch/um/drivers/ubd_kern.c        |   4 +-
 arch/um/include/shared/irq_user.h |  12 +-
 arch/um/include/shared/os.h       |  17 +-
 arch/um/kernel/irq.c              | 460 ++++++++++++++++++++++++--------------
 arch/um/os-Linux/irq.c            | 202 +++++++++--------
 8 files changed, 444 insertions(+), 317 deletions(-)

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index acbe6c67afba..05588f9466c7 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -171,56 +171,19 @@ int enable_chan(struct line *line)
 	return err;
 }
 
-/* Items are added in IRQ context, when free_irq can't be called, and
- * removed in process context, when it can.
- * This handles interrupt sources which disappear, and which need to
- * be permanently disabled.  This is discovered in IRQ context, but
- * the freeing of the IRQ must be done later.
- */
-static DEFINE_SPINLOCK(irqs_to_free_lock);
-static LIST_HEAD(irqs_to_free);
-
-void free_irqs(void)
-{
-	struct chan *chan;
-	LIST_HEAD(list);
-	struct list_head *ele;
-	unsigned long flags;
-
-	spin_lock_irqsave(&irqs_to_free_lock, flags);
-	list_splice_init(&irqs_to_free, &list);
-	spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-
-	list_for_each(ele, &list) {
-		chan = list_entry(ele, struct chan, free_list);
-
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
-}
-
 static void close_one_chan(struct chan *chan, int delay_free_irq)
 {
-	unsigned long flags;
-
 	if (!chan->opened)
 		return;
 
-	if (delay_free_irq) {
-		spin_lock_irqsave(&irqs_to_free_lock, flags);
-		list_add(&chan->free_list, &irqs_to_free);
-		spin_unlock_irqrestore(&irqs_to_free_lock, flags);
-	}
-	else {
-		if (chan->input && chan->enabled)
-			um_free_irq(chan->line->driver->read_irq, chan);
-		if (chan->output && chan->enabled)
-			um_free_irq(chan->line->driver->write_irq, chan);
-		chan->enabled = 0;
-	}
+    /* we can safely call free now - it will be marked
+     *  as free and freed once the IRQ stopped processing
+     */
+	if (chan->input && chan->enabled)
+		um_free_irq(chan->line->driver->read_irq, chan);
+	if (chan->output && chan->enabled)
+		um_free_irq(chan->line->driver->write_irq, chan);
+	chan->enabled = 0;
 	if (chan->ops->close != NULL)
 		(*chan->ops->close)(chan->fd, chan->data);
 
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 366e57f5e8d6..8d80b27502e6 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -284,7 +284,7 @@ int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 	if (err)
 		return err;
 	if (output)
-		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
+		err = um_request_irq(driver->write_irq, fd, IRQ_NONE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
 	return err;
diff --git a/arch/um/drivers/random.c b/arch/um/drivers/random.c
index 37c51a6be690..778a0e52d5a5 100644
--- a/arch/um/drivers/random.c
+++ b/arch/um/drivers/random.c
@@ -13,6 +13,7 @@
 #include <linux/miscdevice.h>
 #include <linux/delay.h>
 #include <linux/uaccess.h>
+#include <init.h>
 #include <irq_kern.h>
 #include <os.h>
 
@@ -154,7 +155,14 @@ static int __init rng_init (void)
 /*
  * rng_cleanup - shutdown RNG module
  */
-static void __exit rng_cleanup (void)
+
+static void cleanup(void)
+{
+	free_irq_by_fd(random_fd);
+	os_close_file(random_fd);
+}
+
+static void __exit rng_cleanup(void)
 {
 	os_close_file(random_fd);
 	misc_deregister (&rng_miscdev);
@@ -162,6 +170,7 @@ static void __exit rng_cleanup (void)
 
 module_init (rng_init);
 module_exit (rng_cleanup);
+__uml_exitcall(cleanup);
 
 MODULE_DESCRIPTION("UML Host Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index b55fe9bf5d3e..d4e8c497ae86 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1587,11 +1587,11 @@ int io_thread(void *arg)
 
 		do {
 			res = os_write_file(kernel_fd, ((char *) io_req_buffer) + written, n);
-			if (res > 0) {
+			if (res >= 0) {
 				written += res;
 			} else {
 				if (res != -EAGAIN) {
-					printk("io_thread - read failed, fd = %d, "
+					printk("io_thread - write failed, fd = %d, "
 					       "err = %d\n", kernel_fd, -n);
 				}
 			}
diff --git a/arch/um/include/shared/irq_user.h b/arch/um/include/shared/irq_user.h
index df5633053957..a7a6120f19d5 100644
--- a/arch/um/include/shared/irq_user.h
+++ b/arch/um/include/shared/irq_user.h
@@ -7,6 +7,7 @@
 #define __IRQ_USER_H__
 
 #include <sysdep/ptrace.h>
+#include <stdbool.h>
 
 struct irq_fd {
 	struct irq_fd *next;
@@ -15,10 +16,17 @@ struct irq_fd {
 	int type;
 	int irq;
 	int events;
-	int current_events;
+	bool active;
+	bool pending;
+	bool purge;
 };
 
-enum { IRQ_READ, IRQ_WRITE };
+#define IRQ_READ  0
+#define IRQ_WRITE 1
+#define IRQ_NONE 2
+#define MAX_IRQ_TYPE (IRQ_NONE + 1)
+
+
 
 struct siginfo;
 extern void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs);
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 574e03fc7ba2..edbe6563d5c5 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -290,15 +290,16 @@ extern void halt_skas(void);
 extern void reboot_skas(void);
 
 /* irq.c */
-extern int os_waiting_for_events(struct irq_fd *active_fds);
-extern int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds);
-extern void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2);
-extern void os_free_irq_later(struct irq_fd *active_fds,
-		int irq, void *dev_id);
-extern int os_get_pollfd(int i);
-extern void os_set_pollfd(int i, int fd);
+extern int os_waiting_for_events_epoll(void);
+extern void *os_epoll_get_data_pointer(int index);
+extern int os_epoll_triggered(int index, int events);
+extern int os_event_mask(int irq_type);
+extern int os_setup_epoll(void);
+extern int os_add_epoll_fd(int events, int fd, void *data);
+extern int os_mod_epoll_fd(int events, int fd, void *data);
+extern int os_del_epoll_fd(int fd);
 extern void os_set_ioignore(void);
+extern void os_close_epoll_fd(void);
 
 /* sigio.c */
 extern int add_sigio_fd(int fd);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 23cb9350d47e..980148d56537 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -1,4 +1,6 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
@@ -16,243 +18,361 @@
 #include <as-layout.h>
 #include <kern_util.h>
 #include <os.h>
+#include <irq_user.h>
 
-/*
- * This list is accessed under irq_lock, except in sigio_handler,
- * where it is safe from being modified.  IRQ handlers won't change it -
- * if an IRQ source has vanished, it will be freed by free_irqs just
- * before returning from sigio_handler.  That will process a separate
- * list of irqs to free, with its own locking, coming back here to
- * remove list elements, taking the irq_lock to do so.
+
+/* When epoll triggers we do not know why it did so
+ * we can also have different IRQs for read and write.
+ * This is why we keep a small irq_fd array for each fd -
+ * one entry per IRQ type
  */
-static struct irq_fd *active_fds = NULL;
-static struct irq_fd **last_irq_ptr = &active_fds;
 
-extern void free_irqs(void);
+struct irq_entry {
+	struct irq_entry *next;
+	int fd;
+	struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
+};
+
+static struct irq_entry *active_fds;
+
+static DEFINE_SPINLOCK(irq_lock);
+
+static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
+{
+/*
+ * irq->active guards against reentry
+ * irq->pending accumulates pending requests
+ * if pending is raised the irq_handler is re-run
+ * until pending is cleared
+ */
+	if (irq->active) {
+		irq->active = false;
+		do {
+			irq->pending = false;
+			do_IRQ(irq->irq, regs);
+		} while (irq->pending && (!irq->purge));
+		if (!irq->purge)
+			irq->active = true;
+	} else {
+		irq->pending = true;
+	}
+}
 
 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
-	struct irq_fd *irq_fd;
-	int n;
+	struct irq_entry *irq_entry;
+	struct irq_fd *irq;
+
+	int n, i, j;
 
 	while (1) {
-		n = os_waiting_for_events(active_fds);
+		/* This is now lockless - epoll keeps back-referencesto the irqs
+		 * which have trigger it so there is no need to walk the irq
+		 * list and lock it every time. We avoid locking by turning off
+		 * IO for a specific fd by executing os_del_epoll_fd(fd) before
+		 * we do any changes to the actual data structures
+		 */
+		n = os_waiting_for_events_epoll();
+
 		if (n <= 0) {
 			if (n == -EINTR)
 				continue;
-			else break;
+			else
+				break;
 		}
 
-		for (irq_fd = active_fds; irq_fd != NULL;
-		     irq_fd = irq_fd->next) {
-			if (irq_fd->current_events != 0) {
-				irq_fd->current_events = 0;
-				do_IRQ(irq_fd->irq, regs);
+		for (i = 0; i < n ; i++) {
+			/* Epoll back reference is the entry with 3 irq_fd
+			 * leaves - one for each irq type.
+			 */
+			irq_entry = (struct irq_entry *)
+				os_epoll_get_data_pointer(i);
+			for (j = 0; j < MAX_IRQ_TYPE ; j++) {
+				irq = irq_entry->irq_array[j];
+				if (irq == NULL)
+					continue;
+				if (os_epoll_triggered(i, irq->events) > 0)
+					irq_io_loop(irq, regs);
+				if (irq->purge) {
+					irq_entry->irq_array[j] = NULL;
+					kfree(irq);
+				}
 			}
 		}
 	}
+}
+
+static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
+{
+	int i;
+	int events = 0;
+	struct irq_fd *irq;
 
-	free_irqs();
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		irq = irq_entry->irq_array[i];
+		if (irq != NULL)
+			events = irq->events | events;
+	}
+	if (events > 0) {
+	/* os_add_epoll will call os_mod_epoll if this already exists */
+		return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
+	}
+	/* No events - delete */
+	return os_del_epoll_fd(irq_entry->fd);
 }
 
-static DEFINE_SPINLOCK(irq_lock);
+
 
 static int activate_fd(int irq, int fd, int type, void *dev_id)
 {
-	struct pollfd *tmp_pfd;
-	struct irq_fd *new_fd, *irq_fd;
+	struct irq_fd *new_fd;
+	struct irq_entry *irq_entry;
+	int i, err, events;
 	unsigned long flags;
-	int events, err, n;
 
 	err = os_set_fd_async(fd);
 	if (err < 0)
 		goto out;
 
-	err = -ENOMEM;
-	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
-	if (new_fd == NULL)
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
 
-	if (type == IRQ_READ)
-		events = UM_POLLIN | UM_POLLPRI;
-	else events = UM_POLLOUT;
-	*new_fd = ((struct irq_fd) { .next  		= NULL,
-				     .id 		= dev_id,
-				     .fd 		= fd,
-				     .type 		= type,
-				     .irq 		= irq,
-				     .events 		= events,
-				     .current_events 	= 0 } );
+	/* Check if we have an entry for this fd */
 
 	err = -EBUSY;
-	spin_lock_irqsave(&irq_lock, flags);
-	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
-		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
-			printk(KERN_ERR "Registering fd %d twice\n", fd);
-			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
-			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
-			       dev_id);
+	for (irq_entry = active_fds;
+		irq_entry != NULL; irq_entry = irq_entry->next) {
+		if (irq_entry->fd == fd)
+			break;
+	}
+
+	if (irq_entry == NULL) {
+		/* This needs to be atomic as it may be called from an
+		 * IRQ context.
+		 */
+		irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
+		if (irq_entry == NULL) {
+			printk(KERN_ERR
+				"Failed to allocate new IRQ entry\n");
 			goto out_unlock;
 		}
+		irq_entry->fd = fd;
+		for (i = 0; i < MAX_IRQ_TYPE; i++)
+			irq_entry->irq_array[i] = NULL;
+		irq_entry->next = active_fds;
+		active_fds = irq_entry;
 	}
 
-	if (type == IRQ_WRITE)
-		fd = -1;
-
-	tmp_pfd = NULL;
-	n = 0;
+	/* Check if we are trying to re-register an interrupt for a
+	 * particular fd
+	 */
 
-	while (1) {
-		n = os_create_pollfd(fd, events, tmp_pfd, n);
-		if (n == 0)
-			break;
+	if (irq_entry->irq_array[type] != NULL) {
+		printk(KERN_ERR
+			"Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
+			irq, fd, type, dev_id
+		);
+		goto out_unlock;
+	} else {
+		/* New entry for this fd */
+
+		err = -ENOMEM;
+		new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
+		if (new_fd == NULL)
+			goto out_unlock;
 
-		/*
-		 * n > 0
-		 * It means we couldn't put new pollfd to current pollfds
-		 * and tmp_fds is NULL or too small for new pollfds array.
-		 * Needed size is equal to n as minimum.
-		 *
-		 * Here we have to drop the lock in order to call
-		 * kmalloc, which might sleep.
-		 * If something else came in and changed the pollfds array
-		 * so we will not be able to put new pollfd struct to pollfds
-		 * then we free the buffer tmp_fds and try again.
+		events = os_event_mask(type);
+
+		*new_fd = ((struct irq_fd) {
+			.id		= dev_id,
+			.irq		= irq,
+			.type		= type,
+			.events		= events,
+			.active		= true,
+			.pending	= false,
+			.purge		= false
+		});
+		/* Turn off any IO on this fd - allows us to
+		 * avoid locking the IRQ loop
 		 */
-		spin_unlock_irqrestore(&irq_lock, flags);
-		kfree(tmp_pfd);
-
-		tmp_pfd = kmalloc(n, GFP_KERNEL);
-		if (tmp_pfd == NULL)
-			goto out_kfree;
-
-		spin_lock_irqsave(&irq_lock, flags);
+		os_del_epoll_fd(irq_entry->fd);
+		irq_entry->irq_array[type] = new_fd;
 	}
 
-	*last_irq_ptr = new_fd;
-	last_irq_ptr = &new_fd->next;
-
+	/* Turn back IO on with the correct (new) IO event mask */
+	assign_epoll_events_to_irq(irq_entry);
 	spin_unlock_irqrestore(&irq_lock, flags);
-
-	/*
-	 * This calls activate_fd, so it has to be outside the critical
-	 * section.
-	 */
-	maybe_sigio_broken(fd, (type == IRQ_READ));
+	maybe_sigio_broken(fd, (type != IRQ_NONE));
 
 	return 0;
-
- out_unlock:
+out_unlock:
 	spin_unlock_irqrestore(&irq_lock, flags);
- out_kfree:
-	kfree(new_fd);
- out:
+out:
 	return err;
 }
 
-static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
+/*
+ * Walk the IRQ list and dispose of any unused entries.
+ * Should be done under irq_lock.
+ */
+
+static void garbage_collect_irq_entries(void)
 {
-	unsigned long flags;
+	int i;
+	bool reap;
+	struct irq_entry *walk;
+	struct irq_entry *previous = NULL;
+	struct irq_entry *to_free;
 
-	spin_lock_irqsave(&irq_lock, flags);
-	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
-	spin_unlock_irqrestore(&irq_lock, flags);
+	if (active_fds == NULL)
+		return;
+	walk = active_fds;
+	while (walk != NULL) {
+		reap = true;
+		for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+			if (walk->irq_array[i] != NULL) {
+				reap = false;
+				break;
+			}
+		}
+		if (reap) {
+			if (previous == NULL)
+				active_fds = walk->next;
+			else
+				previous->next = walk->next;
+			to_free = walk;
+		} else {
+			to_free = NULL;
+		}
+		walk = walk->next;
+		if (to_free != NULL)
+			kfree(to_free);
+	}
 }
 
-struct irq_and_dev {
-	int irq;
-	void *dev;
-};
+/*
+ * Walk the IRQ list and get the descriptor for our FD
+ */
 
-static int same_irq_and_dev(struct irq_fd *irq, void *d)
+static struct irq_entry *get_irq_entry_by_fd(int fd)
 {
-	struct irq_and_dev *data = d;
+	struct irq_entry *walk = active_fds;
 
-	return ((irq->irq == data->irq) && (irq->id == data->dev));
+	while (walk != NULL) {
+		if (walk->fd == fd)
+			return walk;
+		walk = walk->next;
+	}
+	return NULL;
 }
 
-static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
-{
-	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
-							  .dev  = dev });
 
-	free_irq_by_cb(same_irq_and_dev, &data);
-}
+/*
+ * Walk the IRQ list and dispose of an entry for a specific
+ * device, fd and number. Note - if sharing an IRQ for read
+ * and writefor the same FD it will be disposed in either case.
+ * If this behaviour is undesirable use different IRQ ids.
+ */
 
-static int same_fd(struct irq_fd *irq, void *fd)
-{
-	return (irq->fd == *((int *)fd));
-}
+#define IGNORE_IRQ 1
+#define IGNORE_DEV (1<<1)
 
-void free_irq_by_fd(int fd)
+static void do_free_by_irq_and_dev(
+	struct irq_entry *irq_entry,
+	unsigned int irq,
+	void *dev,
+	int flags
+)
 {
-	free_irq_by_cb(same_fd, &fd);
+	int i;
+	struct irq_fd *to_free;
+
+	for (i = 0; i < MAX_IRQ_TYPE ; i++) {
+		if (irq_entry->irq_array[i] != NULL) {
+			if (
+			((flags & IGNORE_IRQ) ||
+				(irq_entry->irq_array[i]->irq == irq)) &&
+			((flags & IGNORE_DEV) ||
+				(irq_entry->irq_array[i]->id == dev))
+			) {
+				/* Turn off any IO on this fd - allows us to
+				 * avoid locking the IRQ loop
+				 */
+				os_del_epoll_fd(irq_entry->fd);
+				to_free = irq_entry->irq_array[i];
+				irq_entry->irq_array[i] = NULL;
+				assign_epoll_events_to_irq(irq_entry);
+				if (to_free->active)
+					to_free->purge = true;
+				else
+					kfree(to_free);
+			}
+		}
+	}
 }
 
-/* Must be called with irq_lock held */
-static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
+void free_irq_by_fd(int fd)
 {
-	struct irq_fd *irq;
-	int i = 0;
-	int fdi;
+	struct irq_entry *to_free;
+	unsigned long flags;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		if ((irq->fd == fd) && (irq->irq == irqnum))
-			break;
-		i++;
-	}
-	if (irq == NULL) {
-		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
-		       fd);
-		goto out;
-	}
-	fdi = os_get_pollfd(i);
-	if ((fdi != -1) && (fdi != fd)) {
-		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
-		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
-		       fdi, fd);
-		irq = NULL;
-		goto out;
+	spin_lock_irqsave(&irq_lock, flags);
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
 	}
-	*index_out = i;
- out:
-	return irq;
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
 }
 
-void reactivate_fd(int fd, int irqnum)
+static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irq,
+			dev,
+			0
+		);
+		to_free = to_free->next;
 	}
-	os_set_pollfd(i, irq->fd);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
+}
 
-	add_sigio_fd(fd);
+
+void reactivate_fd(int fd, int irqnum)
+{
+	/** NOP - we do auto-EOI now **/
 }
 
 void deactivate_fd(int fd, int irqnum)
 {
-	struct irq_fd *irq;
+	struct irq_entry *to_free;
 	unsigned long flags;
-	int i;
 
+	os_del_epoll_fd(fd);
 	spin_lock_irqsave(&irq_lock, flags);
-	irq = find_irq_by_fd(fd, irqnum, &i);
-	if (irq == NULL) {
-		spin_unlock_irqrestore(&irq_lock, flags);
-		return;
+	to_free = get_irq_entry_by_fd(fd);
+	if (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			irqnum,
+			NULL,
+			IGNORE_DEV
+		);
 	}
-
-	os_set_pollfd(i, -1);
+	garbage_collect_irq_entries();
 	spin_unlock_irqrestore(&irq_lock, flags);
-
 	ignore_sigio_fd(fd);
 }
 EXPORT_SYMBOL(deactivate_fd);
@@ -265,17 +385,28 @@ EXPORT_SYMBOL(deactivate_fd);
  */
 int deactivate_all_fds(void)
 {
-	struct irq_fd *irq;
-	int err;
+	unsigned long flags;
+	struct irq_entry *to_free;
 
-	for (irq = active_fds; irq != NULL; irq = irq->next) {
-		err = os_clear_fd_async(irq->fd);
-		if (err)
-			return err;
-	}
-	/* If there is a signal already queued, after unblocking ignore it */
+	spin_lock_irqsave(&irq_lock, flags);
+	/* Stop IO. The IRQ loop has no lock so this is our
+	 * only way of making sure we are safe to dispose
+	 * of all IRQ handlers
+	 */
 	os_set_ioignore();
-
+	to_free = active_fds;
+	while (to_free != NULL) {
+		do_free_by_irq_and_dev(
+			to_free,
+			-1,
+			NULL,
+			IGNORE_IRQ | IGNORE_DEV
+		);
+		to_free = to_free->next;
+	}
+	garbage_collect_irq_entries();
+	spin_unlock_irqrestore(&irq_lock, flags);
+	os_close_epoll_fd();
 	return 0;
 }
 
@@ -353,8 +484,11 @@ void __init init_IRQ(void)
 
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
+
 	for (i = 1; i < NR_IRQS; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
+	/* Initialize EPOLL Loop */
+	os_setup_epoll();
 }
 
 /*
diff --git a/arch/um/os-Linux/irq.c b/arch/um/os-Linux/irq.c
index b9afb74b79ad..365823010346 100644
--- a/arch/um/os-Linux/irq.c
+++ b/arch/um/os-Linux/irq.c
@@ -1,135 +1,147 @@
 /*
+ * Copyright (C) 2017 - Cambridge Greys Ltd
+ * Copyright (C) 2011 - 2014 Cisco Systems Inc
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
 
 #include <stdlib.h>
 #include <errno.h>
-#include <poll.h>
+#include <sys/epoll.h>
 #include <signal.h>
 #include <string.h>
 #include <irq_user.h>
 #include <os.h>
 #include <um_malloc.h>
 
+/* Epoll support */
+
+static int epollfd = -1;
+
+#define MAX_EPOLL_EVENTS 64
+
+static struct epoll_event epoll_events[MAX_EPOLL_EVENTS];
+
+/* Helper to return an Epoll data pointer from an epoll event structure.
+ * We need to keep this one on the userspace side to keep includes separate
+ */
+
+void *os_epoll_get_data_pointer(int index)
+{
+	return epoll_events[index].data.ptr;
+}
+
+/* Helper to compare events versus the events in the epoll structure.
+ * Same as above - needs to be on the userspace side
+ */
+
+
+int os_epoll_triggered(int index, int events)
+{
+	return epoll_events[index].events & events;
+}
+/* Helper to set the event mask.
+ * The event mask is opaque to the kernel side, because it does not have
+ * access to the right includes/defines for EPOLL constants.
+ */
+
+int os_event_mask(int irq_type)
+{
+	if (irq_type == IRQ_READ)
+		return EPOLLIN | EPOLLPRI;
+	if (irq_type == IRQ_WRITE)
+		return EPOLLOUT;
+	return 0;
+}
+
 /*
- * Locked by irq_lock in arch/um/kernel/irq.c.  Changed by os_create_pollfd
- * and os_free_irq_by_cb, which are called under irq_lock.
+ * Initial Epoll Setup
  */
-static struct pollfd *pollfds = NULL;
-static int pollfds_num = 0;
-static int pollfds_size = 0;
+int os_setup_epoll(void)
+{
+	epollfd = epoll_create(MAX_EPOLL_EVENTS);
+	return epollfd;
+}
 
-int os_waiting_for_events(struct irq_fd *active_fds)
+/*
+ * Helper to run the actual epoll_wait
+ */
+int os_waiting_for_events_epoll(void)
 {
-	struct irq_fd *irq_fd;
-	int i, n, err;
+	int n, err;
 
-	n = poll(pollfds, pollfds_num, 0);
+	n = epoll_wait(epollfd,
+		(struct epoll_event *) &epoll_events, MAX_EPOLL_EVENTS, 0);
 	if (n < 0) {
 		err = -errno;
 		if (errno != EINTR)
-			printk(UM_KERN_ERR "os_waiting_for_events:"
-			       " poll returned %d, errno = %d\n", n, errno);
+			printk(
+				UM_KERN_ERR "os_waiting_for_events:"
+				" epoll returned %d, error = %s\n", n,
+				strerror(errno)
+			);
 		return err;
 	}
-
-	if (n == 0)
-		return 0;
-
-	irq_fd = active_fds;
-
-	for (i = 0; i < pollfds_num; i++) {
-		if (pollfds[i].revents != 0) {
-			irq_fd->current_events = pollfds[i].revents;
-			pollfds[i].fd = -1;
-		}
-		irq_fd = irq_fd->next;
-	}
 	return n;
 }
 
-int os_create_pollfd(int fd, int events, void *tmp_pfd, int size_tmpfds)
-{
-	if (pollfds_num == pollfds_size) {
-		if (size_tmpfds <= pollfds_size * sizeof(pollfds[0])) {
-			/* return min size needed for new pollfds area */
-			return (pollfds_size + 1) * sizeof(pollfds[0]);
-		}
-
-		if (pollfds != NULL) {
-			memcpy(tmp_pfd, pollfds,
-			       sizeof(pollfds[0]) * pollfds_size);
-			/* remove old pollfds */
-			kfree(pollfds);
-		}
-		pollfds = tmp_pfd;
-		pollfds_size++;
-	} else
-		kfree(tmp_pfd);	/* remove not used tmp_pfd */
-
-	pollfds[pollfds_num] = ((struct pollfd) { .fd		= fd,
-						  .events	= events,
-						  .revents	= 0 });
-	pollfds_num++;
-
-	return 0;
-}
 
-void os_free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg,
-		struct irq_fd *active_fds, struct irq_fd ***last_irq_ptr2)
+/*
+ * Helper to add a fd to epoll
+ */
+int os_add_epoll_fd(int events, int fd, void *data)
 {
-	struct irq_fd **prev;
-	int i = 0;
-
-	prev = &active_fds;
-	while (*prev != NULL) {
-		if ((*test)(*prev, arg)) {
-			struct irq_fd *old_fd = *prev;
-			if ((pollfds[i].fd != -1) &&
-			    (pollfds[i].fd != (*prev)->fd)) {
-				printk(UM_KERN_ERR "os_free_irq_by_cb - "
-				       "mismatch between active_fds and "
-				       "pollfds, fd %d vs %d\n",
-				       (*prev)->fd, pollfds[i].fd);
-				goto out;
-			}
-
-			pollfds_num--;
-
-			/*
-			 * This moves the *whole* array after pollfds[i]
-			 * (though it doesn't spot as such)!
-			 */
-			memmove(&pollfds[i], &pollfds[i + 1],
-			       (pollfds_num - i) * sizeof(pollfds[0]));
-			if (*last_irq_ptr2 == &old_fd->next)
-				*last_irq_ptr2 = prev;
-
-			*prev = (*prev)->next;
-			if (old_fd->type == IRQ_WRITE)
-				ignore_sigio_fd(old_fd->fd);
-			kfree(old_fd);
-			continue;
-		}
-		prev = &(*prev)->next;
-		i++;
-	}
- out:
-	return;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events | EPOLLET;
+	result = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
+	if ((result) && (errno == EEXIST))
+		result = os_mod_epoll_fd(events, fd, data);
+	if (result)
+		printk("epollctl add err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-int os_get_pollfd(int i)
+/*
+ * Helper to mod the fd event mask and/or data backreference
+ */
+int os_mod_epoll_fd(int events, int fd, void *data)
 {
-	return pollfds[i].fd;
+	struct epoll_event event;
+	int result;
+
+	event.data.ptr = data;
+	event.events = events;
+	result = epoll_ctl(epollfd, EPOLL_CTL_MOD, fd, &event);
+	if (result)
+		printk(UM_KERN_ERR
+			"epollctl mod err fd %d, %s\n", fd, strerror(errno));
+	return result;
 }
 
-void os_set_pollfd(int i, int fd)
+/*
+ * Helper to delete the epoll fd
+ */
+int os_del_epoll_fd(int fd)
 {
-	pollfds[i].fd = fd;
+	struct epoll_event event;
+	int result;
+	/* This is quiet as we use this as IO ON/OFF - so it is often
+	 * invoked on a non-existent fd
+	 */
+	result = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
+	return result;
 }
 
 void os_set_ioignore(void)
 {
 	signal(SIGIO, SIG_IGN);
 }
+
+void os_close_epoll_fd(void)
+{
+	/* Needed so we do not leak an fd when rebooting */
+	os_close_file(epollfd);
+}
-- 
2.11.0

[uml-devel] PATCH v7

[<ant...@ko...>]

This is hopefully the final parking position. It has been cleaned up,
updated to fit the current netdev warning/info message conventions
and no longer hangs if the underlying network hard xmit misbehaves.

The issue with raw sockets is a definitive BUG - I have gone through
it with a comb several times, including sticking debug into the
actual host af_packet itself. If you try to give af_packet.c a TSO
frame it does something to it which makes the TSO capable underlying
device drop it. The same frame passes tap with flying colors.
Go figure.

A.

Re: [uml-devel] [thomas@m3y3r.de: Re: [PATCH] um: Fix kcov crash before kernel is started.]

[Mark R. <mar...@ar...>]

Hi,

On Tue, Oct 10, 2017 at 10:59:23AM +0200, 'Dmitry Vyukov' via syzkaller wrote:
> On Mon, Oct 9, 2017 at 9:16 PM, Thomas Meyer <th...@m3...> wrote:
> >> > Date: Sun, 8 Oct 2017 13:18:24 +0200
> >> > From: Thomas Meyer <th...@m3...>
> >> > To: Richard Weinberger <ri...@no...>
> >> > Cc: use...@li..., lin...@vg...
> >> > Subject: Re: [PATCH] um: Fix kcov crash before kernel is started.
> >> > User-Agent: NeoMutt/20170113 (1.7.2)
> >> >
> >> > On Sun, Oct 08, 2017 at 12:44:12PM +0200, Richard Weinberger wrote:
> >> >> Am Sonntag, 8. Oktober 2017, 12:31:58 CEST schrieb Thomas Meyer:
> >> >> > UMLs current_thread_info() unconditionally assumes that the top of the stack
> >> >> > contains the thread_info structure. But on UML the __sanitizer_cov_trace_pc
> >> >> > function is called for *all* functions! This results in an early crash:
> >> >> >
> >> >> > Prevent kcov from using invalid curent_thread_info() data by checking
> >> >> > the system_state.
> >> >> >
> >> >> > Signed-off-by: Thomas Meyer <th...@m3...>

[...]

> >> Yes, kcov can have some issues with early bootstrap code, because it
> >> accesses current and it can also conflict with say, per-cpu setup code
> >> (at least it was the case for x86). For x86 and arm64 we just bulk
> >> blacklist instrumentation of arch code involved in early bootstrap.
> >> See e.g. KCOV_INSTRUMENT in arch/x86/boot/Makefile. I think you need
> >> to do the same for um. Start with bulk ignoring as much as possible
> >> until you get it booting and then bisect back from there.
> >
> > oh, arch/um/* already contains the Makefile exception settings!
> > I guess CONFIG_KCOV_INSTRUMENT_ALL overrides the the Makefile settings?
> > Or doesn't it? I looked at scripts/Makefile.lib but failed to understand
> > what config options has precedens in that case.
> 
> Then, I guess, boot code calls into some common instrumented code,
> which gets into kcov and crashes.
> 
> This check helps, right?
> 
> +#ifdef CONFIG_UML
> +   if(!(system_state == SYSTEM_SCHEDULING ||
> +        system_state == SYSTEM_RUNNING))
> +           return;
> +#endif
> 
> Which means we somehow get here during boot. Is it possible to get a
> stack trace for the return statement?
> 
> There is no common recipe. I think x86/arm64 are somewhat fragile in
> this aspect as well, but somehow work. First of all we need to
> understand how we get into the instrumentation callback during boot.

Small info dump below. I *think* arm64 is mostly ok.

On arm64, our get_current() reads a system register that we setup in
early assembly with a pointer to our task struct. Our thread_info is
embedded in our task_struct.

That's setup in {primary,secondary}_switched, before we execute most C
code, including early init code like kasan_early_init and
kaslr_early_init, so it's safe to use current_thread_info() even in
those early bootstrap functions.

The only exception that I'm aware of is the EFI stub. However, that
isn't permitted to make calls to most kernel functions, and in its
makefile we (try to) enforce that it only calls into uninstrumented
position-independent functions. So any problems should be apparent at
build time.

There are a few special files (e.g. the out-of-line LL/SC atomics) which
we need to disable instrumentation for, which I intend to send patches
for at some point soon.

Thanks,
Mark.