linux-kernel - [PATCH v8 05/11] KVM: x86/mmu: Rearrange kvm_{test_,}age

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Message-ID: <20241105184333.2305744-6-jthoughton@google.com>
Date: Tue,  5 Nov 2024 18:43:27 +0000
From: James Houghton <jthoughton@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: David Matlack <dmatlack@...gle.com>, David Rientjes <rientjes@...gle.com>, 
	James Houghton <jthoughton@...gle.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Wei Xu <weixugc@...gle.com>, Yu Zhao <yuzhao@...gle.com>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v8 05/11] KVM: x86/mmu: Rearrange kvm_{test_,}age_gfn

Reorder the TDP MMU check to be first for both kvm_test_age_gfn and
kvm_age_gfn. For kvm_test_age_gfn, this allows us to completely avoid
needing to grab the MMU lock when the TDP MMU reports that the page is
young. Do the same for kvm_age_gfn merely for consistency.

Signed-off-by: James Houghton <jthoughton@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 26797ccd34d8..793565a3a573 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1586,15 +1586,15 @@ 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;
 }
 
@@ -1602,15 +1602,15 @@ 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;
 }
 
-- 
2.47.0.199.ga7371fff76-goog