linux-kernel - [PATCH v2 13/22] KVM: x86/mmu: Always walk guest PTEs with WRITE access when unprotecting

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Message-ID: <20240831001538.336683-14-seanjc@google.com>
Date: Fri, 30 Aug 2024 17:15:28 -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 13/22] KVM: x86/mmu: Always walk guest PTEs with WRITE
 access when unprotecting

When getting a gpa from a gva to unprotect the associated gfn when an
event is awating reinjection, walk the guest PTEs for WRITE as there's no
point in unprotecting the gfn if the guest is unable to write the page,
i.e. if write-protection can't trigger emulation.

Note, the entire flow should be guarded on the access being a write, and
even better should be conditioned on actually triggering a write-protect
fault.  This will be addressed in a future commit.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ee288f8370de..b89e2c63b435 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2751,7 +2751,7 @@ static int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
 	if (vcpu->arch.mmu->root_role.direct)
 		return 0;

-	gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);
+	gpa = kvm_mmu_gva_to_gpa_write(vcpu, gva, NULL);
 	if (gpa == INVALID_GPA)
 		return 0;

-- 
2.46.0.469.g59c65b2a67-goog