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

[Wanpeng Li]

2018-04-18 18:36 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
> 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).

How about the live migration? What will happen if the source and
destination machines have different microcode version?

Regards,
Wanpeng Li