Re: [PATCH 0/7] KVM: x86: hyper-v: make KVM_GET_SUPPORTED_HV_CPUID more useful

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes:

> KVM_GET_SUPPORTED_HV_CPUID was initially implemented as a vCPU ioctl but
> this is not very useful when VMM is just trying to query which Hyper-V
> features are supported by the host prior to creating VM/vCPUs. The data
> in KVM_GET_SUPPORTED_HV_CPUID is mostly static with a few exceptions but
> it seems we can change this. Add support for KVM_GET_SUPPORTED_HV_CPUID as
> a system ioctl as well.
>
> QEMU specific description:
> In some cases QEMU needs to collect the information about which Hyper-V
> features are supported by KVM and pass it up the stack. For non-hyper-v
> features this is done with system-wide KVM_GET_SUPPORTED_CPUID/
> KVM_GET_MSRS ioctls but Hyper-V specific features don't get in the output
> (as Hyper-V CPUIDs intersect with KVM's). In QEMU, CPU feature expansion
> happens before any KVM vcpus are created so KVM_GET_SUPPORTED_HV_CPUID
> can't be used in its current shape.
>

Ping ;-)

I know Hyper-V emulation in KVM is a very specific topic so it's not
very easy to find reviewers but I'd be very happy if someone could
provide any feedback on the idea (above) in general.

-- 
Vitaly