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[Xen-changelog] Improve configuration of virtual device drivers in XenLinux.
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From: BitKeeper B. <ri...@su...> - 2004-09-16 14:01:20
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ChangeSet 1.1317, 2004/09/16 14:11:34+01:00, ka...@fr...
Improve configuration of virtual device drivers in XenLinux.
arch/xen/Kconfig | 67 ++++++++++++++++++++++++++++++++++---
arch/xen/configs/xen0_defconfig | 5 ++
arch/xen/configs/xenU_defconfig | 5 ++
arch/xen/i386/mm/ioremap.c | 5 --
drivers/xen/Makefile | 8 ++--
drivers/xen/netfront/netfront.c | 23 ++++++++----
include/asm-xen/asm-i386/pgalloc.h | 2 -
7 files changed, 92 insertions(+), 23 deletions(-)
diff -Nru a/linux-2.6.8.1-xen-sparse/arch/xen/Kconfig b/linux-2.6.8.1-xen-sparse/arch/xen/Kconfig
--- a/linux-2.6.8.1-xen-sparse/arch/xen/Kconfig 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/arch/xen/Kconfig 2004-09-16 10:01:08 -04:00
@@ -31,9 +31,68 @@
Support for privileged operation (domain 0)
config XEN_PHYSDEV_ACCESS
- bool "Device-driver domain (physical device access)"
+ bool "Physical device access"
+ default y if XEN_PRIVILEGED_GUEST
+ default n if !XEN_PRIVILEGED_GUEST
help
- Device-driver domain (physical device access)
+ Assume access is available to physical hardware devices
+ (e.g., hard drives, network cards). This allows you to configure
+ such devices and also includes some low-level support that is
+ otherwise not compiled into the kernel.
+
+config XEN_BLKDEV_BACKEND
+ bool "Block-device backend driver"
+ default y if XEN_PHYSDEV_ACCESS
+ default n if !XEN_PHYSDEV_ACCESS
+ help
+ The block-device backend driver allows the kernel to export its
+ block devices to other guests via a high-performance shared-memory
+ interface.
+
+config XEN_NETDEV_BACKEND
+ bool "Network-device backend driver"
+ default y if XEN_PHYSDEV_ACCESS
+ default n if !XEN_PHYSDEV_ACCESS
+ help
+ The network-device backend driver allows the kernel to export its
+ network devices to other guests via a high-performance shared-memory
+ interface.
+
+config XEN_BLKDEV_FRONTEND
+ bool "Block-device frontend driver"
+ default y
+ help
+ The block-device frontend driver allows the kernel to access block
+ devices mounted within another guest OS. Unless you are building a
+ dedicated device-driver domain, or your master control domain
+ (domain 0), then you almost certainly want to say Y here.
+
+config XEN_NETDEV_FRONTEND
+ bool "Network-device frontend driver"
+ default y
+ help
+ The network-device frontend driver allows the kernel to access
+ network interfaces within another guest OS. Unless you are building a
+ dedicated device-driver domain, or your master control domain
+ (domain 0), then you almost certainly want to say Y here.
+
+if XEN_NETDEV_FRONTEND
+config XEN_NETDEV_FRONTEND_PIPELINED_TRANSMITTER
+ bool "Pipelined transmitter (DANGEROUS)"
+ default n
+ help
+ The driver will assume that the backend is pipelining packets for
+ transmission: whenever packets are pending in the remote backend,
+ the driver will not send asynchronous notifications when it queues
+ additional packets for transmission.
+ If the backend is a dumb domain, such as a transparent Ethernet
+ bridge with no local IP interface, it is safe to say Y here to get
+ slightly lower network overhead.
+ If the backend has a local IP interface; or may be doing smart things
+ like reassembling packets to perform firewall filtering; or if you
+ are unsure; or if you experience network hangs when this option is
+ enabled; then you must say N here.
+endif
config XEN_WRITABLE_PAGETABLES
bool "Use writable pagetables"
@@ -49,8 +108,8 @@
config PAGESIZED_SKBS
bool
- default y if XEN_PHYSDEV_ACCESS
- default n if !XEN_PHYSDEV_ACCESS
+ default y if XEN_NETDEV_BACKEND
+ default n if !XEN_NETDEV_BACKEND
#config VT
# bool
diff -Nru a/linux-2.6.8.1-xen-sparse/arch/xen/configs/xen0_defconfig b/linux-2.6.8.1-xen-sparse/arch/xen/configs/xen0_defconfig
--- a/linux-2.6.8.1-xen-sparse/arch/xen/configs/xen0_defconfig 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/arch/xen/configs/xen0_defconfig 2004-09-16 10:01:08 -04:00
@@ -10,6 +10,11 @@
#
CONFIG_XEN_PRIVILEGED_GUEST=y
CONFIG_XEN_PHYSDEV_ACCESS=y
+CONFIG_XEN_BLKDEV_BACKEND=y
+CONFIG_XEN_NETDEV_BACKEND=y
+CONFIG_XEN_BLKDEV_FRONTEND=y
+CONFIG_XEN_NETDEV_FRONTEND=y
+# CONFIG_XEN_NETDEV_FRONTEND_PIPELINED_TRANSMITTER is not set
CONFIG_XEN_WRITABLE_PAGETABLES=y
CONFIG_FOREIGN_PAGES=y
CONFIG_PAGESIZED_SKBS=y
diff -Nru a/linux-2.6.8.1-xen-sparse/arch/xen/configs/xenU_defconfig b/linux-2.6.8.1-xen-sparse/arch/xen/configs/xenU_defconfig
--- a/linux-2.6.8.1-xen-sparse/arch/xen/configs/xenU_defconfig 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/arch/xen/configs/xenU_defconfig 2004-09-16 10:01:08 -04:00
@@ -10,6 +10,11 @@
#
# CONFIG_XEN_PRIVILEGED_GUEST is not set
# CONFIG_XEN_PHYSDEV_ACCESS is not set
+# CONFIG_XEN_BLKDEV_BACKEND is not set
+# CONFIG_XEN_NETDEV_BACKEND is not set
+CONFIG_XEN_BLKDEV_FRONTEND=y
+CONFIG_XEN_NETDEV_FRONTEND=y
+# CONFIG_XEN_NETDEV_FRONTEND_PIPELINED_TRANSMITTER is not set
CONFIG_XEN_WRITABLE_PAGETABLES=y
CONFIG_FOREIGN_PAGES=y
# CONFIG_PAGESIZED_SKBS is not set
diff -Nru a/linux-2.6.8.1-xen-sparse/arch/xen/i386/mm/ioremap.c b/linux-2.6.8.1-xen-sparse/arch/xen/i386/mm/ioremap.c
--- a/linux-2.6.8.1-xen-sparse/arch/xen/i386/mm/ioremap.c 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/arch/xen/i386/mm/ioremap.c 2004-09-16 10:01:08 -04:00
@@ -337,8 +337,6 @@
#endif /* CONFIG_XEN_PHYSDEV_ACCESS */
-#if defined(CONFIG_XEN_PRIVILEGED_GUEST)
-
/* These hacky macros avoid phys->machine translations. */
#define __direct_pte(x) ((pte_t) { (x) } )
#define __direct_mk_pte(page_nr,pgprot) \
@@ -481,6 +479,3 @@
return 0;
}
-
-
-#endif /* CONFIG_XEN_PRIVILEGED_GUEST */
diff -Nru a/linux-2.6.8.1-xen-sparse/drivers/xen/Makefile b/linux-2.6.8.1-xen-sparse/drivers/xen/Makefile
--- a/linux-2.6.8.1-xen-sparse/drivers/xen/Makefile 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/drivers/xen/Makefile 2004-09-16 10:01:08 -04:00
@@ -1,11 +1,11 @@
-obj-y += blkfront/
obj-y += console/
obj-y += evtchn/
-obj-y += netfront/
obj-y += privcmd/
-obj-$(CONFIG_XEN_PHYSDEV_ACCESS) += blkback/
-obj-$(CONFIG_XEN_PHYSDEV_ACCESS) += netback/
+obj-$(CONFIG_XEN_BLKDEV_BACKEND) += blkback/
+obj-$(CONFIG_XEN_NETDEV_BACKEND) += netback/
+obj-$(CONFIG_XEN_BLKDEV_FRONTEND) += blkfront/
+obj-$(CONFIG_XEN_NETDEV_FRONTEND) += netfront/
diff -Nru a/linux-2.6.8.1-xen-sparse/drivers/xen/netfront/netfront.c b/linux-2.6.8.1-xen-sparse/drivers/xen/netfront/netfront.c
--- a/linux-2.6.8.1-xen-sparse/drivers/xen/netfront/netfront.c 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/drivers/xen/netfront/netfront.c 2004-09-16 10:01:08 -04:00
@@ -40,6 +40,19 @@
#define __GFP_NOWARN 0
#endif
+/*
+ * If the backend driver is pipelining transmit requests then we can be very
+ * aggressive in avoiding new-packet notifications -- only need to send a
+ * notification if there are no outstanding unreceived responses.
+ * If the backend may be buffering our transmit buffers for any reason then we
+ * are rather more conservative.
+ */
+#ifdef CONFIG_XEN_NETDEV_FRONTEND_PIPELINED_TRANSMITTER
+#define TX_TEST_IDX resp_prod /* aggressive: any outstanding responses? */
+#else
+#define TX_TEST_IDX req_cons /* conservative: not seen all our requests? */
+#endif
+
static void network_tx_buf_gc(struct net_device *dev);
static void network_alloc_rx_buffers(struct net_device *dev);
@@ -408,15 +421,9 @@
np->stats.tx_bytes += skb->len;
np->stats.tx_packets++;
- /* Only notify Xen if there are no outstanding responses. */
- /*
- * KAF (16/9/04): Checking outstanding responses is unsafe, as pending work
- * may be dependent on packets not yet seen by the backend (e.g., he may
- * have a partially-assembled fragmented IP packet). For now, the check is
- * more conservative -- has the backend seen all previous requests?
- */
+ /* Only notify Xen if we really have to. */
mb();
- if ( np->tx->req_cons/*resp_prod*/ == i )
+ if ( np->tx->TX_TEST_IDX == i )
notify_via_evtchn(np->evtchn);
return 0;
diff -Nru a/linux-2.6.8.1-xen-sparse/include/asm-xen/asm-i386/pgalloc.h b/linux-2.6.8.1-xen-sparse/include/asm-xen/asm-i386/pgalloc.h
--- a/linux-2.6.8.1-xen-sparse/include/asm-xen/asm-i386/pgalloc.h 2004-09-16 10:01:08 -04:00
+++ b/linux-2.6.8.1-xen-sparse/include/asm-xen/asm-i386/pgalloc.h 2004-09-16 10:01:08 -04:00
@@ -53,7 +53,6 @@
#define check_pgt_cache() do { } while (0)
-#ifdef CONFIG_XEN_PRIVILEGED_GUEST
int direct_remap_area_pages(struct mm_struct *mm,
unsigned long address,
unsigned long machine_addr,
@@ -64,6 +63,5 @@
unsigned long address,
unsigned long size,
mmu_update_t *v);
-#endif /* CONFIG_XEN_PRIVILEGED_GUEST */
#endif /* _I386_PGALLOC_H */
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