Re: [PATCH] KVM: X86: Allow userspace to define the microcode version

From: Paolo Bonzini
Date: Wed Apr 18 2018 - 06:36:45 EST

On 18/04/2018 11:03, Eduardo Habkost wrote:
>>> QEMU setting ucode_rev automatically using the host value when
>>> using "-cpu host" (with no need for explicit ucode_rev option)
>>> makes sense to me.
>> QEMU can't get the host value by rdmsr MSR_IA32_UCODE_REV directly
>> since rdmsr will #GP when ring !=0, any idea?
> By looking at kvm_get_msr_feature(), it looks like
> ioctl(system_fd, KVM_GET_MSRS) would return the host MSR value
> for us.

Yes, that's exactly what it was introduced for (together with other MSRs
including VMX capabilities).