[Qemu-devel] Migration - Random guest kernel panics on target

[Fennosys]

Hi,

I'm encountering random guest kernel crashes while doing live migration with 
qemu (using qemu cli and monitor commands). 

QEMU emulator version 2.10.0
Host kernel: 4.13.9-gentoo
Guest kernel: 4.13.9-gentoo

Host cpu: 
model name      : AMD Opteron(tm) Processor 6128
stepping        : 1
microcode       : 0x10000d9


example of vm starup cli: 
qemu-system-x86_64 -daemonize -name VM50 -vnc :50 -enable-kvm -cpu host -serial 
file:/var/log/kvm/50-serial.log -k fi \
-kernel /somepath/bzImage \
root=/dev/vda -m 4096 -smp 4 -runas kvm-user \
-netdev 
type=tap,ifname=vm50,id=VM50,script=/etc/openvswitch/scripts/ifup-br0-50,downscript=/etc/openvswitch/scripts/ifdown-br0,vhost=on
 \
-device virtio-net-pci,mac=xx:xx:xx:xx:xx:xx,netdev=VM50 \
-drive file=/dev/drbd1,format=raw,if=virtio

backtrace:
[  370.984297] BUG: unable to handle kernel paging request at ffffcc40fe000020
[  370.985542] IP: receive_buf+0x7db/0xd20
[  370.986131] PGD 0 
[  370.986132] P4D 0 
[  370.986450] 
[  370.987463] Oops: 0000 [#1] SMP
[  370.987972] Modules linked in: kvm_amd kvm irqbypass
[  370.988787] CPU: 1 PID: 14 Comm: ksoftirqd/1 Not tainted 4.13.9-gentoo #3
[  370.989816] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
1.10.2-1.fc27 04/01/2014
[  370.991131] task: ffff8ec1baae6c00 task.stack: ffff9cd9406b0000
[  370.992018] RIP: 0010:receive_buf+0x7db/0xd20
[  370.992673] RSP: 0018:ffff9cd9406b3d10 EFLAGS: 00010286
[  370.993454] RAX: 0000713f00000000 RBX: 00000000000007dd RCX: 0000000000002b9d
[  370.994508] RDX: ffffca7c00000000 RSI: ffff9cd9406b3d4c RDI: ffff8ec1ba11c000
[  370.995571] RBP: ffff9cd9406b3d98 R08: 0000000000000000 R09: 0000000000000600
[  370.996618] R10: ffffcc40fe000000 R11: ffff8ec1ba44d740 R12: ffff8ec1ba10f800
[  370.997676] R13: ffff8ec1b9bf2400 R14: 0000000080000000 R15: ffff8ec1b9bf2d00
[  370.998728] FS:  0000000000000000(0000) GS:ffff8ec1bfc80000(0000) 
knlGS:0000000000000000
[  370.999924] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  371.000770] CR2: ffffcc40fe000020 CR3: 000000013a551000 CR4: 00000000000006a0
[  371.001828] Call Trace:
[  371.002231]  ? load_balance+0x144/0x970
[  371.002802]  virtnet_poll+0x14e/0x260
[  371.003433]  net_rx_action+0x1ab/0x2b0
[  371.003996]  __do_softirq+0xdb/0x1e0
[  371.004558]  run_ksoftirqd+0x24/0x50
[  371.005107]  smpboot_thread_fn+0x107/0x160
[  371.005718]  kthread+0xff/0x140
[  371.006195]  ? sort_range+0x20/0x20
[  371.006725]  ? kthread_create_on_node+0x40/0x40
[  371.007415]  ret_from_fork+0x25/0x30
[  371.007965] Code: 0a 8c 00 4d 01 f2 72 0e 48 c7 c0 00 00 00 80 48 2b 05 ba 
6e 8e 00 49 01 c2 48 8b 15 a0 6e 8e 00 49 c1 ea 0c 49 c1 e2 06 49 01 d2 <49> 8b 
42 20 a8 01 48 8d 48 ff 8b 45 b4 4c 0f 45 d1 49 39 c1 0f 
[  371.010846] RIP: receive_buf+0x7db/0xd20 RSP: ffff9cd9406b3d10
[  371.011701] CR2: ffffcc40fe000020
[  371.012241] ---[ end trace b32e281709829620 ]---
[  371.012929] Kernel panic - not syncing: Fatal exception in interrupt
[  371.013999] Kernel Offset: 0x31000000 from 0xffffffff81000000 (relocation 
range: 0xffffffff80000000-0xffffffffbfffffff)
[  371.015543] ---[ end Kernel panic - not syncing: Fatal exception in interrupt

conditions:
With low work-load the migration seems to perform as expected. 

If load average is between 3-4 the issue can be reproduced relatively easily 
(2-5 live migration till it's crashing).

The drbd block device is in dual primary mode during the migration.

RAM (ECC) on both hosts has been tested before these test.

Cheers,
Antti


-- 
Fennosys <address@hidden>