linux-kernel - [PATCH v6 08/11] KVM: x86: Optimize kvm_{test_,}age

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Message-ID: <20240724011037.3671523-9-jthoughton@google.com>
Date: Wed, 24 Jul 2024 01:10:33 +0000
From: James Houghton <jthoughton@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Paolo Bonzini <pbonzini@...hat.com>
Cc: Ankit Agrawal <ankita@...dia.com>, Axel Rasmussen <axelrasmussen@...gle.com>, 
	Catalin Marinas <catalin.marinas@....com>, David Matlack <dmatlack@...gle.com>, 
	David Rientjes <rientjes@...gle.com>, James Houghton <jthoughton@...gle.com>, 
	James Morse <james.morse@....com>, Jason Gunthorpe <jgg@...pe.ca>, Jonathan Corbet <corbet@....net>, 
	Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Raghavendra Rao Ananta <rananta@...gle.com>, Ryan Roberts <ryan.roberts@....com>, 
	Sean Christopherson <seanjc@...gle.com>, Shaoqin Huang <shahuang@...hat.com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Wei Xu <weixugc@...gle.com>, 
	Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>, Zenghui Yu <yuzenghui@...wei.com>, 
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v6 08/11] KVM: x86: Optimize kvm_{test_,}age_gfn a little bit

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.

Also, for kvm_test_age_gfn, reorder the TDP MMU check to be first. If we
find that the range is young, we do not need to check the shadow MMU.

Signed-off-by: James Houghton <jthoughton@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7b93ce8f0680..919d59385f89 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1629,19 +1629,24 @@ static void rmap_add(struct kvm_vcpu *vcpu, const struct kvm_memory_slot *slot,
 	__rmap_add(vcpu->kvm, cache, slot, spte, gfn, access);
 }
 
+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;
 
-	if (kvm_memslots_have_rmaps(kvm)) {
+	if (tdp_mmu_enabled)
+		young |= kvm_tdp_mmu_age_gfn_range(kvm, range);
+
+	if (kvm_has_shadow_mmu_sptes(kvm)) {
 		write_lock(&kvm->mmu_lock);
 		young = kvm_handle_gfn_range(kvm, range, kvm_age_rmap);
 		write_unlock(&kvm->mmu_lock);
 	}
 
-	if (tdp_mmu_enabled)
-		young |= kvm_tdp_mmu_age_gfn_range(kvm, range);
-
 	return young;
 }
 
@@ -1649,15 +1654,15 @@ 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_has_shadow_mmu_sptes(kvm)) {
 		write_lock(&kvm->mmu_lock);
 		young = kvm_handle_gfn_range(kvm, range, kvm_test_age_rmap);
 		write_unlock(&kvm->mmu_lock);
 	}
 
-	if (tdp_mmu_enabled)
-		young |= kvm_tdp_mmu_test_age_gfn(kvm, range);
-
 	return young;
 }
 
-- 
2.46.0.rc1.232.g9752f9e123-goog