Re: [uml-user] PC change, and errors in have_xstate_support

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On 13/02/17 at 03:47, Dan Milon wrote:
> Yes, CPU matters apparently. I got hit by this badly.
> 
> I traced the chain of calls into the kernel, and apparently this has to
> do with fpu related features.
> you have to set eagerfpu=off in your kernel boot options. Also note that
> there is a 6 options limit. Any option after the 6th will be ignored.

This is a sad news. Anyway, with this option I have the same problem. To
make everything worse, I though my system was running with my patch, but
in reality no xterm is opened and the guest systemd is reporting a lot
of errors.

Proof of eagerfpu disabled in the host:

[    0.000000] Linux version 4.9.8-1-ARCH (builduser@tobias) (gcc version 6.3.1 20170109 (GCC) ) #1 SMP PREEMPT Mon Feb 6 12:59:40 CET 2017
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-linux eagerfpu=off root=UUID=ba5db090-54da-4c66-b75d-51e7047f38f7 rw quiet
[    0.000000] x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x18.
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'compacted' format.
[    0.000000] x86/fpu: Using 'lazy' FPU context switches.

My patch leads to the following:

Core dump limits :
	soft - NONE
	hard - NONE
Checking that ptrace can change system call numbers...OK
Checking syscall emulation patch for ptrace...OK
Checking advanced syscall emulation patch for ptrace...OK
Checking environment variables for a tempdir.../tmp/nat
Checking if /tmp/nat is on tmpfs...OK
Checking PROT_EXEC mmap in /tmp/nat...OK
Adding 26710016 bytes to physical memory to account for exec-shield gap
Linux version 4.10.0-rc8-uml-00205-g7089db84e356-dirty (nat@judith) (gcc version 6.3.1 20170109 (GCC) ) #19 Mon Feb 13 16:32:53 CET 2017
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 135443
Kernel command line: mem=512M ubd0=/home/nat/Work/Linux_UML/fs/fs.ext4 root=98:0
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes)
Inode-cache hash table entries: 65536 (order: 7, 524288 bytes)
Memory: 509592K/550372K available (2647K kernel code, 697K rwdata, 772K rodata, 111K init, 171K bss, 40780K reserved, 0K cma-reserved)
NR_IRQS:15
clocksource: timer: mask: 0xffffffffffffffff max_cycles: 0x1cd42e205, max_idle_ns: 881590404426 ns
Calibrating delay loop... 6955.82 BogoMIPS (lpj=34779136)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 2048 (order: 2, 16384 bytes)
Mountpoint-cache hash table entries: 2048 (order: 2, 16384 bytes)
Checking that host ptys support output SIGIO...Yes
Checking that host ptys support SIGIO on close...No, enabling workaround
devtmpfs: initialized
Using 2.6 host AIO
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
NET: Registered protocol family 16
clocksource: Switched to clocksource timer
VFS: Disk quotas dquot_6.6.0
VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
NET: Registered protocol family 2
TCP established hash table entries: 8192 (order: 4, 65536 bytes)
TCP bind hash table entries: 8192 (order: 4, 65536 bytes)
TCP: Hash tables configured (established 8192 bind 8192)
UDP hash table entries: 512 (order: 2, 16384 bytes)
UDP-Lite hash table entries: 512 (order: 2, 16384 bytes)
NET: Registered protocol family 1
console [stderr0] disabled
mconsole (version 2) initialized on /home/nat/.uml/cbj73V/mconsole
Checking host MADV_REMOVE support...OK
futex hash table entries: 256 (order: 0, 6144 bytes)
workingset: timestamp_bits=46 max_order=17 bucket_order=0
Block layer SCSI generic (bsg) driver version 0.4 loaded (major 254)
io scheduler noop registered
io scheduler deadline registered (default)
NET: Registered protocol family 17
Initialized stdio console driver
Console initialized on /dev/tty0
console [tty0] enabled
Initializing software serial port version 1
console [mc-1] enabled
EXT4-fs (ubda): couldn't mount as ext3 due to feature incompatibilities
EXT4-fs (ubda): couldn't mount as ext2 due to feature incompatibilities
EXT4-fs (ubda): INFO: recovery required on readonly filesystem
EXT4-fs (ubda): write access will be enabled during recovery
EXT4-fs (ubda): recovery complete
EXT4-fs (ubda): mounted filesystem with ordered data mode. Opts: (null)
VFS: Mounted root (ext4 filesystem) readonly on device 98:0.
devtmpfs: mounted
This architecture does not have kernel memory protection.
random: fast init done
systemd[1]: systemd 232 running in system mode. (+PAM -AUDIT -SELINUX -IMA -APPARMOR +SMACK -SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN)
systemd[1]: Detected virtualization uml.
systemd[1]: Detected architecture x86-64.

Welcome to Arch Linux!

systemd[1]: No hostname configured.
systemd[1]: Set hostname to <localhost>.
systemd[1]: Failed to enable kbrequest handling: Inappropriate ioctl for device
systemd[1]: Started Forward Password Requests to Wall Directory Watch.
[  OK  ] Started Forward Password Requests to Wall Directory Watch.
systemd[1]: Reached target Remote File Systems.
[  OK  ] Reached target Remote File Systems.
systemd[1]: Started Dispatch Password Requests to Console Directory Watch.
[  OK  ] Started Dispatch Password Requests to Console Directory Watch.
systemd[1]: Reached target Paths.
[  OK  ] Reached target Paths.
[  OK  ] Listening on udev Kernel Socket.
[  OK  ] Reached target Swap.
[  OK  ] Created slice System Slice.
         Mounting Temporary Directory...
[  OK  ] Listening on Journal Socket (/dev/log).
[  OK  ] Set up automount Arbitrary Executable File Formats File System Automount Point.
[  OK  ] Listening on Process Core Dump Socket.
[  OK  ] Created slice system-getty.slice.
         Mounting POSIX Message Queue File System...
[  OK  ] Listening on LVM2 metadata daemon socket.
[  OK  ] Listening on Journal Socket.
         Starting Apply Kernel Variables...
         Starting Journal Service...
         Starting Remount Root and Kernel File Systems...
[  OK  ] Listening on Device-mapper event daemon FIFOs.
[  OK  ] Created slice User and Session Slice.
[  OK  ] Reached target Slices.
[  OK  ] Listening on udev Control Socket.
[  OK  ] Reached target Encrypted Volumes.
[  OK  ] Listening on /dev/initctl Compatibility Named Pipe.
[  OK  ] Mounted Temporary Directory.
[  OK  ] Mounted POSIX Message Queue File System.
[  OK  ] Started Apply Kernel Variables.
[  OK  ] Started Remount Root and Kernel File Systems.
         Starting udev Coldplug all Devices...
         Starting Load/Save Random Seed...
         Starting Create Static Device Nodes in /dev...
[  OK  ] Started Journal Service.
         Starting Flush Journal to Persistent Storage...
[  OK  ] Started Create Static Device Nodes in /dev.
[  OK  ] Reached target Local File Systems (Pre).
[  OK  ] Reached target Local File Systems.
         Starting udev Kernel Device Manager...
[  OK  ] Started Load/Save Random Seed.
[  OK  ] Started udev Kernel Device Manager.
systemd-journald[42]: Received request to flush runtime journal from PID 1
[  OK  ] Started Flush Journal to Persistent Storage.
         Starting Create Volatile Files and Directories...
[  OK  ] Started udev Coldplug all Devices.
[FAILED] Failed to start Create Volatile Files and Directories.
See 'systemctl status systemd-tmpfiles-setup.service' for details.
         Starting Update UTMP about System Boot/Shutdown...
[FAILED] Failed to start Update UTMP about System Boot/Shutdown.
See 'systemctl status systemd-update-utmp.service' for details.
[  OK  ] Reached target System Initialization.
[  OK  ] Started Daily verification of password and group files.
[  OK  ] Started Daily rotation of log files.
[  OK  ] Started Daily man-db cache update.
[  OK  ] Started Daily Cleanup of Temporary Directories.
[  OK  ] Reached target Timers.
[  OK  ] Listening on D-Bus System Message Bus Socket.
[  OK  ] Reached target Sockets.
[  OK  ] Reached target Basic System.
         Starting Permit User Sessions...
         Starting Login Service...
[  OK  ] Started D-Bus System Message Bus.
[  OK  ] Started Permit User Sessions.
[  OK  ] Started Getty on tty1.
[  OK  ] Reached target Login Prompts.
[  OK  ] Started Login Service.
[  OK  ] Reached target Multi-User System.
Virtual console 1 assigned device '/dev/pts/4'
Virtual console 6 assigned device '/dev/pts/5'

.. and then nothing more, I need to close the console and to manually kill the
processes.

Nat