Re: [PATCH RFC] i386/kvm: fix enlightened VMCS with fine-grained VMX feature enablement

[Paolo Bonzini <pbonzini@redhat.com>]

On 07/01/20 13:08, Vitaly Kuznetsov wrote:
> Honestly I forgot the story why we filtered out these features upon
> eVMCS enablement in KVM. As there are no corresponding eVMCS fields,
> there's no way a guest can actually use them.

Well, mostly because we mimicked what Hyper-V was doing I guess.

> I'm going to check that nothing breaks if we remove the filter. I'll go
> and test Hyper-V 2016 and 2019.

KVM would break, right?  But we can mark that patch as stable material.

Paolo

>> If so, we should teach guest-side KVM about this, not QEMU.
> 
> This is not required when enabling eVMCS on a genuine Hyper-V because it
> correctly filters out unsupported features, however, to not break
> KVM-on-KVM-using-eVMCS case we'll have to move the filter from host to
> guest.
> 
> Thanks!
>