linux-kernel - [PATCH v8 06/11] KVM: x86/mmu: Only check gfn age in shadow MMU if indirect_shadow

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Message-ID: <20241105184333.2305744-7-jthoughton@google.com>
Date: Tue,  5 Nov 2024 18:43:28 +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 06/11] KVM: x86/mmu: Only check gfn age in shadow MMU if
 indirect_shadow_pages > 0

Optimize both kvm_age_gfn and kvm_test_age_gfn's interaction with the
shadow MMU by, rather than checking if our memslot has rmaps, check if
there are any indirect_shadow_pages at all.

Signed-off-by: James Houghton <jthoughton@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 793565a3a573..125d4c3ccceb 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1582,6 +1582,11 @@ static bool kvm_rmap_age_gfn_range(struct kvm *kvm,
 	return young;
 }
 
+static bool kvm_has_shadow_mmu_sptes(struct kvm *kvm)
+{
+	return !tdp_mmu_enabled || READ_ONCE(kvm->arch.indirect_shadow_pages);
+}
+
 bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
 	bool young = false;
@@ -1589,7 +1594,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 	if (tdp_mmu_enabled)
 		young = kvm_tdp_mmu_age_gfn_range(kvm, range);
 
-	if (kvm_memslots_have_rmaps(kvm)) {
+	if (kvm_has_shadow_mmu_sptes(kvm)) {
 		write_lock(&kvm->mmu_lock);
 		young |= kvm_rmap_age_gfn_range(kvm, range, false);
 		write_unlock(&kvm->mmu_lock);
@@ -1605,7 +1610,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 	if (tdp_mmu_enabled)
 		young = kvm_tdp_mmu_test_age_gfn(kvm, range);
 
-	if (!young && kvm_memslots_have_rmaps(kvm)) {
+	if (!young && kvm_has_shadow_mmu_sptes(kvm)) {
 		write_lock(&kvm->mmu_lock);
 		young |= kvm_rmap_age_gfn_range(kvm, range, true);
 		write_unlock(&kvm->mmu_lock);
-- 
2.47.0.199.ga7371fff76-goog