Re: [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly

Thomas Gleixner
2021-12-11T13:10:56Z

On Sat, Dec 11 2021 at 02:31, Paolo Bonzini wrote:
> On 12/11/21 01:10, Thomas Gleixner wrote:
>> 2) When the guest triggers #NM is takes an VMEXIT and the host
>> does:
>>
>> rdmsrl(MSR_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
>>
>> injects the #NM and goes on.
>>
>> 3) When the guest writes to MSR_XFD_ERR it takes an VMEXIT and
>> the host does:
>>
>> vcpu->arch.guest_fpu.xfd_err = msrval;
>> wrmsrl(MSR_XFD_ERR, msrval);
>
> No wrmsrl here I think, the host value is 0 and should stay so. Instead
> the wrmsrl will happen the next time the VCPU loop is entred.

I assumed this can be handled in the fast path, but either way.