Re: [PATCH v2 02/16] KVM: x86: Refactor GPR accessors to differentiate register access types

[Chang S. Bae]

On 3/4/2026 5:49 PM, Sean Christopherson wrote:
> On Mon, Jan 12, 2026, Chang S. Bae wrote:
> > Refactor the GPR accessors to introduce internal helpers to distinguish
> > between legacy and extended GPRs. Add CONFIG_KVM_APX to selectively
> > enable EGPR support.
>
> Why?  If we really want to make this code efficient, use static calls to wire
> things up if and only if APX is fully supported.

I think the idea was just build out APX-specific code behind the option. 
Ah...sorry, the last sentence was wrong to say.

Yes, I agree on static calls for switching.

> Has anyone done analysis to determine if KVM's currently inlining of
> kvm_register_read() and kvm_register_write() is actually a net positive?  I.e.
> can we just cut over to non-inline functions with static calls?

A quick measurment between inline vs non-inline: When invoked 
repeatedly, the non-inline takes about 5-7% cycles. But, when VM exits 
are involved, the diff goes into a noise level -- e.g. invoking 
accessors 1000 times accounts for about 1% on the exit/entry route.