linux-kernel - [PATCH v2 12/22] KVM: x86/mmu: Don't try to unprotect an INVALID

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Message-ID: <20240831001538.336683-13-seanjc@google.com>
Date: Fri, 30 Aug 2024 17:15:27 -0700
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, 
	Yuan Yao <yuan.yao@...el.com>, Yuan Yao <yuan.yao@...ux.intel.com>
Subject: [PATCH v2 12/22] KVM: x86/mmu: Don't try to unprotect an INVALID_GPA

If getting the gpa for a gva fails, e.g. because the gva isn't mapped in
the guest page tables, don't try to unprotect the invalid gfn.  This is
mostly a performance fix (avoids unnecessarily taking mmu_lock), as
for_each_gfn_valid_sp_with_gptes() won't explode on garbage input, it's
simply pointless.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index dd62bd1e7657..ee288f8370de 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2729,8 +2729,11 @@ bool kvm_mmu_unprotect_gfn_and_retry(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa)
 	if (!READ_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
 		return false;
 
-	if (!vcpu->arch.mmu->root_role.direct)
+	if (!vcpu->arch.mmu->root_role.direct) {
 		gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2_or_gpa, NULL);
+		if (gpa == INVALID_GPA)
+			return false;
+	}
 
 	r = kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa));
 	if (r) {
@@ -2749,6 +2752,8 @@ static int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 		return 0;
 
 	gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);
+	if (gpa == INVALID_GPA)
+		return 0;
 
 	r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);
 
-- 
2.46.0.469.g59c65b2a67-goog