[PATCH v1 11/13] KVM: arm64: Optimize early exit checks in kvm_s2_fault_pin_pfn()

[Joey Gouly]

On Fri, Mar 06, 2026 at 02:02:30PM +0000, Fuad Tabba wrote:
> Optimize the early exit checks in kvm_s2_fault_pin_pfn by grouping all
> error responses under the generic is_error_noslot_pfn check first,
> avoiding unnecessary branches in the hot path.
> 
> Signed-off-by: Fuad Tabba <tabba at google.com>

Reviewed-by: Joey Gouly <joey.gouly at arm.com>

> ---
>  arch/arm64/kvm/mmu.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 2d6e749c1756..9265a7fc43f7 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1791,12 +1791,13 @@ static int kvm_s2_fault_pin_pfn(struct kvm_s2_fault *fault)
>  	fault->pfn = __kvm_faultin_pfn(fault->memslot, fault->gfn,
>  				       fault->write_fault ? FOLL_WRITE : 0,
>  				       &fault->writable, &fault->page);
> -	if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
> -		kvm_send_hwpoison_signal(fault->hva, __ffs(fault->vma_pagesize));
> -		return 0;
> -	}
> -	if (is_error_noslot_pfn(fault->pfn))
> +	if (unlikely(is_error_noslot_pfn(fault->pfn))) {
> +		if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
> +			kvm_send_hwpoison_signal(fault->hva, __ffs(fault->vma_pagesize));
> +			return 0;
> +		}
>  		return -EFAULT;
> +	}
>  
>  	return 1;
>  }
> -- 
> 2.53.0.473.g4a7958ca14-goog
>