Re: [RFC PATCH 0/1] KVM: VMX: restore host CR2 after VM exit

[Konstantin Khorenko]

On 4/22/26 20:56, Sean Christopherson wrote:
...
> > Patch properties:
> >
> >    - Hot path impact: one extra register compare in the common case,
> >      one extra MOV to CR2 under unlikely() when the guest modified CR2.
>
> That's not unlikely.  The odds of guest CR2 matching host CR2 are basically zero.
> In practice, this likely adds two extra CR2 writes on the majority of entry/exit
> transitions.

Thank you very much for the review, Sean.

Agreed on the window: the patch only narrows the exposure, it doesn't close it.

I also mis-sold the cost. "One extra MOV to CR2 under unlikely()" is just wrong, how could i think of 
it, and thus it becomes expensive on a hot path, you are right.

With both points in hand, the patch doesn't carry its weight.
Dropping it.

--
Konstantin