linux-kernel - [PATCH v4 07/11] KVM: x86/mmu: Pivot on "TDP MMU enabled" when handling direct page faults

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Date:   Wed, 12 Oct 2022 18:16:58 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Matlack <dmatlack@...gle.com>,
        Isaku Yamahata <isaku.yamahata@...el.com>
Subject: [PATCH v4 07/11] KVM: x86/mmu: Pivot on "TDP MMU enabled" when
 handling direct page faults

When handling direct page faults, pivot on the TDP MMU being globally
enabled instead of checking if the target MMU is a TDP MMU.  Now that the
TDP MMU is all-or-nothing, if the TDP MMU is enabled, KVM will reach
direct_page_fault() if and only if the MMU is a TDP MMU.  When TDP is
enabled (obviously required for the TDP MMU), only non-nested TDP page
faults reach direct_page_fault(), i.e. nonpaging MMUs are impossible, as
NPT requires paging to be enabled and EPT faults use ept_page_fault().

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 5710be4d328b..fe3aa890a487 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3324,7 +3324,7 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	do {
 		u64 new_spte;
 
-		if (is_tdp_mmu(vcpu->arch.mmu))
+		if (is_tdp_mmu_enabled())
 			sptep = kvm_tdp_mmu_fast_pf_get_last_sptep(vcpu, fault->addr, &spte);
 		else
 			sptep = fast_pf_get_last_sptep(vcpu, fault->addr, &spte);
@@ -4252,7 +4252,6 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
 
 static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 {
-	bool is_tdp_mmu_fault = is_tdp_mmu(vcpu->arch.mmu);
 	int r;
 
 	fault->gfn = fault->addr >> PAGE_SHIFT;
@@ -4275,7 +4274,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 
 	r = RET_PF_RETRY;
 
-	if (is_tdp_mmu_fault)
+	if (is_tdp_mmu_enabled())
 		read_lock(&vcpu->kvm->mmu_lock);
 	else
 		write_lock(&vcpu->kvm->mmu_lock);
@@ -4287,13 +4286,13 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 	if (r)
 		goto out_unlock;
 
-	if (is_tdp_mmu_fault)
+	if (is_tdp_mmu_enabled())
 		r = kvm_tdp_mmu_map(vcpu, fault);
 	else
 		r = __direct_map(vcpu, fault);
 
 out_unlock:
-	if (is_tdp_mmu_fault)
+	if (is_tdp_mmu_enabled())
 		read_unlock(&vcpu->kvm->mmu_lock);
 	else
 		write_unlock(&vcpu->kvm->mmu_lock);
-- 
2.38.0.rc1.362.ged0d419d3c-goog