linux-kernel - [PATCH 21/24] KVM: x86/mmu: Tweak auditing WARN for A/D bits to !PRESENT (was MMIO)

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Date:   Thu, 25 Feb 2021 12:47:46 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 21/24] KVM: x86/mmu: Tweak auditing WARN for A/D bits to
 !PRESENT (was MMIO)

Tweak the MMU_WARN that guards against weirdness when querying A/D status
to fire on a !MMU_PRESENT SPTE, as opposed to a MMIO SPTE.  Attempting to
query A/D status on any kind of !MMU_PRESENT SPTE, MMIO or otherwise,
indicates a KVM bug.  Case in point, several now-fixed bugs were
identified by enabling this new WARN.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/spte.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 645e9bc2d4a2..2fad4ccd3679 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -209,6 +209,11 @@ static inline bool is_mmio_spte(u64 spte)
 	       likely(shadow_mmio_value);
 }
 
+static inline bool is_shadow_present_pte(u64 pte)
+{
+	return !!(pte & SPTE_MMU_PRESENT_MASK);
+}
+
 static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
 {
 	return sp->role.ad_disabled;
@@ -216,13 +221,13 @@ static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
 
 static inline bool spte_ad_enabled(u64 spte)
 {
-	MMU_WARN_ON(is_mmio_spte(spte));
+	MMU_WARN_ON(!is_shadow_present_pte(spte));
 	return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_DISABLED_MASK;
 }
 
 static inline bool spte_ad_need_write_protect(u64 spte)
 {
-	MMU_WARN_ON(is_mmio_spte(spte));
+	MMU_WARN_ON(!is_shadow_present_pte(spte));
 	/*
 	 * This is benign for non-TDP SPTEs as SPTE_TDP_AD_ENABLED_MASK is '0',
 	 * and non-TDP SPTEs will never set these bits.  Optimize for 64-bit
@@ -233,13 +238,13 @@ static inline bool spte_ad_need_write_protect(u64 spte)
 
 static inline u64 spte_shadow_accessed_mask(u64 spte)
 {
-	MMU_WARN_ON(is_mmio_spte(spte));
+	MMU_WARN_ON(!is_shadow_present_pte(spte));
 	return spte_ad_enabled(spte) ? shadow_accessed_mask : 0;
 }
 
 static inline u64 spte_shadow_dirty_mask(u64 spte)
 {
-	MMU_WARN_ON(is_mmio_spte(spte));
+	MMU_WARN_ON(!is_shadow_present_pte(spte));
 	return spte_ad_enabled(spte) ? shadow_dirty_mask : 0;
 }
 
@@ -248,11 +253,6 @@ static inline bool is_access_track_spte(u64 spte)
 	return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0;
 }
 
-static inline bool is_shadow_present_pte(u64 pte)
-{
-	return !!(pte & SPTE_MMU_PRESENT_MASK);
-}
-
 static inline bool is_large_pte(u64 pte)
 {
 	return pte & PT_PAGE_SIZE_MASK;
-- 
2.30.1.766.gb4fecdf3b7-goog