[pve-devel] [PATCH-SERIES v3 qemu-server/manager/common] add and set x86-64-v2 as default model for new vms and detect best cpumodel

[Fiona Ebner]

Am 02.06.23 um 11:13 schrieb DERUMIER, Alexandre:
>>
>> "catastrophic performance collapses" doesn't sound very promising :/
>>
> 
> I have found another thread here:
> https://lore.kernel.org/all/0484ea3f-4ba7-4b93-e976-098c5717166e@redhat.com/
> where paolo have done benchmark with only 3% difference.
> but yes, still slower anyway.

So the "catastrophic performance collapses" might be a bit over the top
or the situation has improved since then for non-paravirtualized locks.
> at minimum, it could be interesting to expose the flag in the gui, for
> users really needed intel-amd migration.
> 

I'm not opposed to that. We could also add a short note to the docs that
it might be worth a try to disable the flag if you need cross-vendor
migration and the default model causes issues. IIRC, from some forum
threads, other people did have success with cross-vendor migration just
selecting kvm64 or Nehalem in the UI, i.e. even with the flag. Likely
depends on concrete host CPU models/kernels whether it's an issue or not.