[PATCH v2 23/28] KVM: x86/mmu: Allow parallel page faults for the TDP MMU

[Ben Gardon]

Make the last few changes necessary to enable the TDP MMU to handle page
faults in parallel while holding the mmu_lock in read mode.

Reviewed-by: Peter Feiner <pfeiner@xxxxxxxxxx>
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b4d6709c240e..3d181a2b2485 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3724,7 +3724,12 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
 		return r;
 
 	r = RET_PF_RETRY;
-	write_lock(&vcpu->kvm->mmu_lock);
+
+	if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+		read_lock(&vcpu->kvm->mmu_lock);
+	else
+		write_lock(&vcpu->kvm->mmu_lock);
+
 	if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
 		goto out_unlock;
 	r = make_mmu_pages_available(vcpu);
@@ -3739,7 +3744,10 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
 				 prefault, is_tdp);
 
 out_unlock:
-	write_unlock(&vcpu->kvm->mmu_lock);
+	if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
+		read_unlock(&vcpu->kvm->mmu_lock);
+	else
+		write_unlock(&vcpu->kvm->mmu_lock);
 	kvm_release_pfn_clean(pfn);
 	return r;
 }
-- 
2.30.0.365.g02bc693789-goog