avx2 cause kernel panic

[jic5760]

cpu-models.conf:

cpu-model: avx
  flags +avx;+avx2
  phys-bits host
  hidden 0
  hv-vendor-id proxmox
  reported-model kvm64

Adding the avx2 option causes a kernel panic.
Both Ubuntu 20.04 & 22.04 are the same.
Is there a bug in qemu?

 

[lmm5247]

cpu-models.conf:

cpu-model: avx
  flags +avx;+avx2
  phys-bits host
  hidden 0
  hv-vendor-id proxmox
  reported-model kvm64

Adding the avx2 option causes a kernel panic.
Both Ubuntu 20.04 & 22.04 are the same.
Is there a bug in qemu?


View attachment 41139

What action did you take to cause the panic? Just setting the CPU type and booting? Or doing a Mongo-based workload using AVX? I'm running the latest Debian 11 with an AVX CPU and it seems to be stable so far, but I haven't spun up Mongo 5 yet...

cpu-model: avx
    flags +avx;+avx2
    phys-bits host
    hidden 0
    hv-vendor-id proxmox
    reported-model kvm64

root@docker05:~# uname -a
Linux docker05 5.10.0-19-amd64 #1 SMP Debian 5.10.149-2 (2022-10-21) x86_64 GNU/Linux

 

[leesteken]

My guess would be that kvm64 does not expose any SSE instructions but software/drivers assume various levels of SSE support when they see support for AVX(2). Maybe add more flags or choose a CPU model that has AVX2 support instead of kvm64.

 

[jic5760]

I just configure CPU as added avx cpu and booted.
The OS was Ubuntu 20.04/22.04.
It has nothing to do with MongoDB as it causes a kernel panic during the boot process.

It works when the cpu is set as the host. As leesteken said, might be able to solve it with an extra flag. I just don't know what those extra flags are.

 

[lmm5247]

Did some experimenting and found that I needed the xsave flag (in addition to avx and avx2) to run MongoDB. See here.

 

[jic5760]

Adding xsave no longer panics! good!