VM crash with UKSM

[eczema]

Hi,

I'm the main developper of eve-ng and we have integrated UKSM in our kernel.
We currently use ubuntu kernel 4.9.40 and we observe a lot of crash on big Qemu VM.

Indeed running 6 Big VM ( 2vCPU + 8G of ram and using a lot of interrupt inside the VM ) is unstable and not safe at all....

I understand that you need information so could you please give a set of required information needed for investigations ?

We could also communicate via mail ( eczema@ecze.com )

[eczema]

sample of error shown on VM

!!!! X64 Exception Type - 00(#DE - Divide Error) CPU Apic ID - 00000000 !!!!
RIP - 00000000BD7DA279, CS - 0000000000000038, RFLAGS - 0000000000010202
RAX - 0000000000001000, RCX - 000000000000000C, RDX - 0000000000000000
RBX - 0000000000001000, RSP - 000000007FBFC930, RBP - 000000007FBFC970
RSI - 0000000000000000, RDI - 00000000BD8BCA98
R8 - 00000000707D3800, R9 - 0000000000000000, R10 - 0000000000000000
R11 - 0000000000000018, R12 - 00000000BD9C3C60, R13 - 00000000BD9C3C68
R14 - 00000000BFB33620, R15 - 00000000BD8C8A98
DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030
GS - 0000000000000030, SS - 0000000000000030
CR0 - 0000000080000033, CR2 - 0000000000000000, CR3 - 00000000BFABA000
CR4 - 0000000000000668, CR8 - 0000000000000000
DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 00000000BFAA8A98 0000000000000047, LDTR - 0000000000000000
IDTR - 00000000BF1DE018 0000000000000FFF, TR - 0000000000000000
FXSAVE_STATE - 000000007FBFC590
!!!! Find PE image (No PDB) (ImageBase=00000000BD7C7000, EntryPoint=00000000BD7D121C) !!!!

[naixia]

Hi, it seems a math calculation error. Is this error from the guest OS inside QEMU or from host OS?
A detailed crash information can be more helpful, here is the previous closed issue example:

#18

[eczema]

The problem occurs on VM provided by Cisco. ( nexus 9000v , a Cisco customised linux ) The issues are not always the same… Sometimes it is one process(not always the same process crash with SIG11, sometimes a kernel failure… ) With UKSM disabled, we never see any issue…. Is there any recommendation regarding Kernel option ( compile ) on the Host ? As we can’t tune the guest Kernel/Os, we can only tune kernel or Qemu options…. Alain

…

On 9 Sep 2017, at 05:22, naixia ***@***.***> wrote: Hi, it seems a math calculation error. Is this error from the guest OS inside QEMU or from host OS? A detailed crash information can be more helpful, here is the previous closed issue example: #18 <#18> — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#25 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGON-PeACZ470NEc83MdYx7NqBZSNQ--ks5sggSBgaJpZM4PRXSM>.

[naixia]

It seems like a data corruption caused by KSM/UKSM.
Recently, upstream kernel detected a KSM data corruption bug that may also affect UKSM.
I backported the bug fix to v4.9, you can have a try. But I am not sure if you came across the same bug.
Apply the patch in a UKSM patched kernel tree:

ksm-data-corruption-v4.9.patch.txt

[eczema]

see here a scheduler crash observed:
Aug 13 15:34:04 eve-ng kernel: INFO: task qemu-system-x86:24307 blocked for more than 120 seconds.
Aug 13 15:34:04 eve-ng kernel: Not tainted 4.9.40-eve-ng-ukms+ #2
Aug 13 15:34:04 eve-ng kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Aug 13 15:34:04 eve-ng kernel: qemu-system-x86 D 0 24307 12933 0x00000000
Aug 13 15:34:04 eve-ng kernel: ffff8bb6c5c5ec80 ffff8bba1a143e00 ffff8bba1a3d2d80 ffff8bbd4b875b00
Aug 13 15:34:04 eve-ng kernel: ffff8bba226d9300 ffffa68347d93dd8 ffffffffabe99952 ffff8bba1cfa60a0
Aug 13 15:34:04 eve-ng kernel: 0000000000000246 0000000000000003 0000000000000001 ffff8bbd4b875b00
Aug 13 15:34:04 eve-ng kernel: Call Trace:
Aug 13 15:34:04 eve-ng kernel: [] ? __schedule+0x232/0x6f0
Aug 13 15:34:04 eve-ng kernel: [] schedule+0x36/0x80
Aug 13 15:34:04 eve-ng kernel: [] jbd2_log_wait_commit+0x98/0x120
Aug 13 15:34:04 eve-ng kernel: [] ? wake_atomic_t_function+0x60/0x60
Aug 13 15:34:04 eve-ng kernel: [] jbd2_complete_transaction+0x5c/0xa0
Aug 13 15:34:04 eve-ng kernel: [] ext4_sync_file+0x1ef/0x3e0
Aug 13 15:34:04 eve-ng kernel: [] vfs_fsync_range+0x4b/0xb0
Aug 13 15:34:04 eve-ng kernel: [] ? SyS_futex+0x81/0x180
Aug 13 15:34:04 eve-ng kernel: [] do_fsync+0x3d/0x70
Aug 13 15:34:04 eve-ng kernel: [] SyS_fdatasync+0x13/0x20
Aug 13 15:34:04 eve-ng kernel: [] entry_SYSCALL_64_fastpath+0x1e/0xad
Aug 13 15:39:02 eve-ng CRON[25770]: pam_unix(cron:session): session opened for user root by (uid=0)

[eczema]

I did not test yet your patch... I will launch a compile and test...

[eczema]

is this bug could be related to :
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1680513 ?

[eczema]

Currently testing the last patch...
Seems ok... 7 x 8go RAM running with total memory used reduced to 18 Go... and no more process crash.... :-)

[naixia]

Glad to hear that. This fix will be included in UKSM for v4.13 and later versions.

[eczema]

I confirm...
This bug was the culprit for multiple issue observed.. Right now, uksm is just incredibly effective:
No more system instability - freezes of process - qemu crash - etc etc ... Now , runs so smoothly. It is awesome....

Regards and Hat off !!!

[anudeep404]

Looks like I hit the same bug, I'm using EVE-NG version: 2.0.3-86,QEMU version: 2.4.0.
root@eve-ng:/var/log# uname -a
Linux eve-ng 4.9.40-eve-ng-ukms-2+ #4 SMP Fri Sep 15 02:07:02 CEST 2017 x86_64 x86_64 x86_64 GNU/Linux

I'm using a VM with 64 vCPUs and 128 gigs of RAM.

When I try to run more than 10 Nexus NK9's, I see the crashes and the 11th VM goes into boot loop. How do I fix this?

[dolohow]

Please create new bug report. With stacktrace and more information attached.

[anudeep404]

I upgraded kernel to 4.14.44 and i'm still seeing the problem..will open a new bug. Thanks.

root@eve-ng:~# uname -a
Linux eve-ng 4.14.44 #1 SMP Sat May 26 20:12:35 EEST 2018 x86_64 x86_64 x86_64 GNU/Linux

[Laynvedb]

Currently testing the last patch...
Seems ok... 7 x 8go RAM running with total memory used reduced to 18 Go... and no more process crash.... :-)

Can you tell me how to patch it? Which patch?
I also encountered the same problem. kernel is 4.9.40-eve-ng-ukms-2+

[xinbinhan]

这个问题解决了吗？