Re: [PATCH v2 05/25] KVM: x86/mmu: rephrase unclear comment

[Sean Christopherson]

On Mon, Feb 21, 2022, Paolo Bonzini wrote:
> If accessed bits are not supported there simple isn't any distinction
> between accessed and non-accessed gPTEs, so the comment does not make
> much sense.  Rephrase it in terms of what happens if accessed bits
> *are* supported.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
>  arch/x86/kvm/mmu/paging_tmpl.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 80b4b291002a..d1d17d28e81b 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -193,7 +193,7 @@ static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
>  	if (!FNAME(is_present_gpte)(gpte))
>  		goto no_present;
>  
> -	/* if accessed bit is not supported prefetch non accessed gpte */
> +	/* if accessed bit is supported, prefetch only accessed gpte */

Can we just reword the whole thing?  A/D bits being disabled is the anomaly,
leading with the "if" makes the logic we really care about seem like a secondary
concern.  E.g.

	/* Prefetch only accessed entries (unless A/D bits are disabled). */

>  	if (PT_HAVE_ACCESSED_DIRTY(vcpu->arch.mmu) &&
>  	    !(gpte & PT_GUEST_ACCESSED_MASK))
>  		goto no_present;
> -- 
> 2.31.1
> 
>