linux-kernel - [RFC PATCH v2 42/69] KVM: x86/mmu: Explicitly check for MMIO spte in fast page fault

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Message-Id: <26005d563a9303ecc6ca68a9baea77895a75e8e0.1625186503.git.isaku.yamahata@intel.com>
Date:   Fri,  2 Jul 2021 15:04:48 -0700
From:   isaku.yamahata@...el.com
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [RFC PATCH v2 42/69] KVM: x86/mmu: Explicitly check for MMIO spte in fast page fault

From: Sean Christopherson <sean.j.christopherson@...el.com>

Explicity check for an MMIO spte in the fast page fault flow.  TDX will
use a not-present entry for MMIO sptes, which can be mistaken for an
access-tracked spte since both have SPTE_SPECIAL_MASK set.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.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 990ee645b8a2..631b92e6e9ba 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3060,7 +3060,7 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			break;
 
 		sp = sptep_to_sp(iterator.sptep);
-		if (!is_last_spte(spte, sp->role.level))
+		if (!is_last_spte(spte, sp->role.level) || is_mmio_spte(spte))
 			break;
 
 		/*
-- 
2.25.1