[pve-devel] [PATCH-SERIES qemu-server/manager v2 0/8] VM CPU flags: introduce vendor-agnostic 'nested-virt' CPU flag

[Daniel Kral]

On Fri Nov 7, 2025 at 3:43 PM CET, Fiona Ebner wrote:
> Changes in v2 (thanks Dano and Thomas!):
> * 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.
> * Drop adding non-existing link in API end point.
> * Keep $supported_cpu_flags private to module and add getter method.
> * Unpack @_ first at the beginning of resolve_cpu_flags().
> * ui: fix function call in the CPU flag selector widget.
> * ui: use simpler method to get all records of the store.
> * Drop already applied patches.

Had another look at the patches and tested the same as last time
(different combinations of {+,-}nested-virt and {+,-}vmx on Intel host
in custom cpu model and cpu flags).

As I don't have a mixed-vendor (AMD/Intel) cluster ready, I couldn't
test whether the migration would abort if e.g. I were to live migrate a
VM with "+svm" to a Intel host, but from an off-list demonstration from
@Fiona and the code I assume that this works the same as starting a VM
with "+svm" on an Intel host, which results in the fatal error below:

kvm: warning: host doesn't support requested feature: CPUID[eax=80000001h].ECX.svm [bit 2]
kvm: Host doesn't support requested features

Otherwise, the changes from v1 to v2 and the patches overall look good
to me, so consider this as:

Reviewed-by: Daniel Kral <d.kral at proxmox.com>
Tested-by: Daniel Kral <d.kral at proxmox.com>