[PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

Explicitly detect and disallow private accesses to emulated MMIO in
kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private()
to perform the check.  This will allow the page fault path to go straight
to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn().

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20240228024147.41573-12-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a8e14c2b68a7..fdae6d19e72b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3262,6 +3262,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
 {
 	gva_t gva = fault->is_tdp ? 0 : fault->addr;
 
+	if (fault->is_private) {
+		kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
+		return -EFAULT;
+	}
+
 	vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
 			     access & shadow_mmio_access_mask);
 
-- 
2.43.0