[PATCH v6 08/11] KVM: x86: Optimize kvm_{test_,}age_gfn a little bit

[James Houghton]

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 at google.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