[pve-devel] applied: [PATCH qemu-server v2 4/8] cpu config: introduce vendor-agnostic 'nested-virt' CPU flag

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 07.11.25 um 15:44 schrieb Fiona Ebner:
> The flag will automatically resolve to the flag required for the
> current CPU on the host. The 'nested-virt' flag takes precendence over
> the CPU-specific flag for nesting which might already be present with
> custom CPU models. In that case, a warning is printed.
> 
> Also make sure that the actual resolved flag is passed along during
> live migration, since the nested-virt flag can resolve differently on
> different hosts.
> 
> Suggested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> ---
> 
> Changes in v2:
> * Pass running CPU configuration when using 'nested-virt'. This
>   ensures that migration fails early if the flag resolves differently
>   on the target.
> * Describe that live migration still only works if it's the same flag.
> 
> I was thinking about using special characters in the flag name or some
> custom-/pve-/special- prefix to distinguish from regular flags, but
> decided against it in the end, because I got the gut feeling it might
> cause more confusion than it helps. Users who are interested in
> details will hopefully read the description and for others, having the
> flag name be direct and descriptive is better.
> 
>  src/PVE/QemuServer/CPUConfig.pm | 52 +++++++++++++++++++++++++++++++--
>  1 file changed, 49 insertions(+), 3 deletions(-)
> 
>

Thanks for your follow-up mail, I tested again with EPYX-v4 vCPU for matching
the AMD EPYC 9475F in my test server and it worked well. Now the virtualization
flag also shows up for the CPU inside the guest from Windows POV, e.g. when
checking in the task managers (CTRL+SHIT+ESC) performance tab.

I amended the commit message with a note for the cpu model, getting some docs
might be nice, especially adapting our nested-virt guide in the wiki with
that info.

applied, thanks!


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