Nested Virtualization with x86-64-v3 CPU Type in Proxmox Cluster

[MrMustard]

Hi everyone,

I have a Proxmox cluster where all my CPUs support the x86-64-v3 CPU type. I'm aiming to enable nested virtualization inside my VMs. While I understand that using the host CPU type would be ideal for this, I need to maintain compatibility across different host CPUs to facilitate live migration, so I'm opting for a virtualized CPU type instead.

While configuring a custom CPU model as described here, I ran into a question. For example, in the following configuration:

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

Does this setup include all the flags from kvm64 in addition to the AVX flags, or does it only include the specified AVX flags?

If I want to use all features of the x86-64-v3 architecture along with virtualization support, would the following configuration be sufficient?

cpu-model: mycputype
    flags +vmx
    reported-model x86-64-v3

Or do I need to manually add all the flags associated with x86-64-v3?

Thanks in advance for your guidance!

 

[fschauer]

Does this setup include all the flags from kvm64 in addition to the AVX flags, or does it only include the specified AVX flags?

This includes the flags from kvm64 and the additionally specified flags from the custom cpu model.

If I want to use all features of the x86-64-v3 architecture along with virtualization support, would the following configuration be sufficient?

cpu-model: mycputype
flags +vmx
reported-model x86-64-v3

Or do I need to manually add all the flags associated with x86-64-v3?

In this case, since x86-64-v3 is not a CPU model known by QEMU, you will need to set reported-model to qemu64 and specify the flags manually according to the $builtin_models in https://git.proxmox.com/?p=qemu-ser...7524f59ceadd562f55a1bf72c3d03d38452f4;hb=HEAD

So it would look like this:

cpu-model: mycputype
    flags +vmx;+aes;+popcnt;+pni;+sse4.1;+sse4.2;+ssse3;+avx;+avx2;+bmi1;+bmi2;+f16c;+fma;+abm;+movbe;+xsave
    reported-model qemu64