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

[Paolo Bonzini]

On 26/02/2018 12:44, Borislav Petkov wrote:
>> The guest write is ignored as the original kvm implementation before the patch.
>
> That will never work because there's no virtualized microcode loader.
> Which will be a dumb idea anyway.
> 
> Goes to show that dealing with microcode revisions for a guest is the
> wrong approach.

I don't understand how one thing follows from the other.  How are writes
to 0x8B related to having a virtualized microcode loaded (which is a
concept that actually makes no sense at all)?

> So that's basically what I'm saying - fix apic_check_deadline_errata()
> to check whether the kernel runs as a guest.

It has already been fixed for a few months, and fixing it is indeed the
right thing to do independent of this patch.

Paolo