[PATCH 11/16] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO

From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	 Yan Zhao <yan.y.zhao@intel.com>,
	Isaku Yamahata <isaku.yamahata@intel.com>,
	 Michael Roth <michael.roth@amd.com>,
	Yu Zhang <yu.c.zhang@linux.intel.com>,
	 Chao Peng <chao.p.peng@linux.intel.com>,
	Fuad Tabba <tabba@google.com>,
	 David Matlack <dmatlack@google.com>
Subject: [PATCH 11/16] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO
Date: Tue, 27 Feb 2024 18:41:42 -0800	[thread overview]
Message-ID: <20240228024147.41573-12-seanjc@google.com> (raw)
In-Reply-To: <20240228024147.41573-1-seanjc@google.com>

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@google.com>
---
 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 5c8caab64ba2..ebdb3fcce3dc 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3314,6 +3314,11 @@ 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);
 
-- 
2.44.0.278.ge034bb2e1d-goog

