Subject: [PATCH v2 11/30] KVM: arm64: Optimize early exit checks in kvm_s2_fault_pin_pfn()

From: Marc Zyngier <[email-masked]>
Date: Fri, 27 Mar 2026 11:35:59 +0000

From: Fuad Tabba <[email-masked]>

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.

Reviewed-by: Joey Gouly <[email-masked]>
Signed-off-by: Fuad Tabba <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 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 2b85daaa4426b..0c71e3a9af8b0 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;
 }
-- 
2.47.3