linux-kernel - [PATCH 08/16] KVM: x86/mmu: WARN and skip MMIO cache on private, reserved page faults

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Message-ID: <20240228024147.41573-9-seanjc@google.com>
Date: Tue, 27 Feb 2024 18:41:39 -0800
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, 
	Yan Zhao <yan.y.zhao@...el.com>, Isaku Yamahata <isaku.yamahata@...el.com>, 
	Michael Roth <michael.roth@....com>, Yu Zhang <yu.c.zhang@...ux.intel.com>, 
	Chao Peng <chao.p.peng@...ux.intel.com>, Fuad Tabba <tabba@...gle.com>, 
	David Matlack <dmatlack@...gle.com>
Subject: [PATCH 08/16] KVM: x86/mmu: WARN and skip MMIO cache on private,
 reserved page faults

WARN and skip the emulated MMIO fastpath if a private, reserved page fault
is encountered, as private+reserved should be an impossible combination
(KVM should never create an MMIO SPTE for a private access).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index bd342ebd0809..9206cfa58feb 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5866,7 +5866,8 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
 		error_code |= PFERR_PRIVATE_ACCESS;
 
 	r = RET_PF_INVALID;
-	if (unlikely(error_code & PFERR_RSVD_MASK)) {
+	if (unlikely((error_code & PFERR_RSVD_MASK) &&
+		     !WARN_ON_ONCE(error_code & PFERR_PRIVATE_ACCESS))) {
 		r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct);
 		if (r == RET_PF_EMULATE)
 			goto emulate;
-- 
2.44.0.278.ge034bb2e1d-goog