From: James Houghton <jthoughton@google.com>
Date: Tue, 4 Feb 2025 00:40:33 +0000 (+0000)
Subject: KVM: x86/mmu: Skip shadow MMU test_young if TDP MMU reports page as young
X-Git-Tag: v6.15-rc1~195^2~11^2~6
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e25c2332346fbd4814d5c9d3d25ba3d0f9646e06;p=thirdparty%2Fkernel%2Flinux.git

KVM: x86/mmu: Skip shadow MMU test_young if TDP MMU reports page as young

Reorder the processing of the TDP MMU versus the shadow MMU when aging
SPTEs, and skip the shadow MMU entirely in the test-only case if the TDP
MMU reports that the page is young, i.e. completely avoid taking mmu_lock
if the TDP MMU SPTE is young.  Swap the order for the test-and-age helper
as well for consistency.

Signed-off-by: James Houghton <jthoughton@google.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Link: https://lore.kernel.org/r/20250204004038.1680123-7-jthoughton@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b73b3c12f76fd..3fc461ebaf055 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1592,15 +1592,15 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
 	bool young = false;
 
+	if (tdp_mmu_enabled)
+		young = kvm_tdp_mmu_age_gfn_range(kvm, range);
+
 	if (kvm_memslots_have_rmaps(kvm)) {
 		write_lock(&kvm->mmu_lock);
-		young = kvm_rmap_age_gfn_range(kvm, range, false);
+		young |= kvm_rmap_age_gfn_range(kvm, range, false);
 		write_unlock(&kvm->mmu_lock);
 	}
 
-	if (tdp_mmu_enabled)
-		young |= kvm_tdp_mmu_age_gfn_range(kvm, range);
-
 	return young;
 }
 
@@ -1608,15 +1608,15 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
 	bool young = false;
 
-	if (kvm_memslots_have_rmaps(kvm)) {
+	if (tdp_mmu_enabled)
+		young = kvm_tdp_mmu_test_age_gfn(kvm, range);
+
+	if (!young && kvm_memslots_have_rmaps(kvm)) {
 		write_lock(&kvm->mmu_lock);
-		young = kvm_rmap_age_gfn_range(kvm, range, true);
+		young |= kvm_rmap_age_gfn_range(kvm, range, true);
 		write_unlock(&kvm->mmu_lock);
 	}
 
-	if (tdp_mmu_enabled)
-		young |= kvm_tdp_mmu_test_age_gfn(kvm, range);
-
 	return young;
 }