Commit 8c403cf2 authored by James Houghton's avatar James Houghton Committed by Sean Christopherson
Browse files

KVM: x86/mmu: Only check gfn age in shadow MMU if indirect_shadow_pages > 0 



When aging SPTEs and the TDP MMU is enabled, process the shadow MMU if and
only if the VM has at least one shadow page, as opposed to checking if the
VM has rmaps.  Checking for rmaps will effectively yield a false positive
if the VM ran nested TDP VMs in the past, but is not currently doing so.

Signed-off-by: default avatarJames Houghton <jthoughton@google.com>
Acked-by: default avatarYu Zhao <yuzhao@google.com>
Link: https://lore.kernel.org/r/20250204004038.1680123-8-jthoughton@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent e25c2332

arch/x86/kvm/mmu/mmu.c

+7 −2
Original line number Diff line number Diff line
@@ -1588,6 +1588,11 @@ static bool kvm_rmap_age_gfn_range(struct kvm *kvm, 
	return young;

}



static bool kvm_may_have_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;
@@ -1595,7 +1600,7 @@ 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_may_have_shadow_mmu_sptes(kvm)) {

		write_lock(&kvm->mmu_lock);

		young |= kvm_rmap_age_gfn_range(kvm, range, false);

		write_unlock(&kvm->mmu_lock);
@@ -1611,7 +1616,7 @@ 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_may_have_shadow_mmu_sptes(kvm)) {

		write_lock(&kvm->mmu_lock);

		young |= kvm_rmap_age_gfn_range(kvm, range, true);

		write_unlock(&kvm->mmu_lock);