[pve-devel] bump default kvm64 cpumodel to a new x86-64-v2 model ?

[pve-devel] bump default kvm64 cpumodel to a new x86-64-v2 model ?

[DERUMIER, Alexandre]

Hi,

Some new distro (rhel/centos/rocky 9  , suse 2023) are begin to build
their packages with -march=x86-64-v2 

This a a initiative from suse/redhat/intel/amd
https://developers.redhat.com/blog/2021/01/05/building-red-hat-enterprise-linux-9-for-the-x86-64-v2-microarchitecture-level#background_of_the_x86_64_microarchitecture_levels

to have compat intel/amd model with more recent cpu flag

That mean than default kvm64 cpumodel is not able to run theses os, and
users are begin to report on the forum

https://forum.proxmox.com/threads/kernel-panic-installing-rocky-or-almalinux.114885/#post-538150

4 models have been determinated:
x86-64-v1 (== qemu64)
x86-64-v2 (v1 + /cx16/&&/lahf/&&/popcnt/&&/sse4_1/&&/sse4_2/&&/ssse3/ )
x86-64-v3 (v2 +
/avx/&&/avx2/&&/bmi1/&&/bmi2/&&/f16c/&&/fma/&&/abm/&&/movbe/&&/xsave/)
x86-64-v4 (v3 +
/avx512f/&&/avx512bw/&&/avx512cd/&&/avx512dq/&&/avx512vl/)

The good news is that x86-64-v2  == intel nahelem cpumodel (2008) and
it's also 100% compatible with Amd since opteron gen4 (2011)


They are some interestring qemu mailing thread about proposal of new
model
https://lore.kernel.org/all/20210526144038.278899-1-berrange@redhat.com/T/

But they never have been applied.


I think it could be great to add at minimum x86-64-v2 model (make a
fake "x86-64-v2" model in qemu-server, using "nahelem" param in qemu),
and use it by default in pve-manager.

Last thing, I think it could be great to add "aes" flag too by default,
but that mean it break "nahelem" compat (2008) for intel, and need
"sandybrige" (2011) model minimum. (amd opteron gen4 from 2011 already
support aes).


Like this, we could have correct performance and compatilibity with
default model.

what do you think about it ?