Move the is_shadow_present_pte() check out of spte_has_volatile_bits()
and into its callers. Well, caller, since only one of its two callers
doesn't already do the shadow-present check.
Opportunistically move the helper to spte.c/h so that it can be used by
the TDP MMU, which is also the primary motivation for the shadow-present
change. Unlike the legacy MMU, the TDP MMU uses a single path for clear
leaf and non-leaf SPTEs, and to avoid unnecessary atomic updates, the TDP
MMU will need to check is_last_spte() prior to calling
spte_has_volatile_bits(), and calling is_last_spte() without first
calling is_shadow_present_spte() is at best odd, and at worst a violation
of KVM's loosely defines SPTE rules.
Note, mmu_spte_clear_track_bits() could likely skip the write entirely
for SPTEs that are not shadow-present. Leave that cleanup for a future
patch to avoid introducing a functional change, and because the
shadow-present check can likely be moved further up the stack, e.g.
drop_large_spte() appears to be the only path that doesn't already
explicitly check for a shadow-present SPTE.
No functional change intended.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 29 ++---------------------------
arch/x86/kvm/mmu/spte.c | 28 ++++++++++++++++++++++++++++
arch/x86/kvm/mmu/spte.h | 2 ++
3 files changed, 32 insertions(+), 27 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 612316768e8e..65b723201738 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -470,32 +470,6 @@ static u64 __get_spte_lockless(u64 *sptep)
}
#endif
-static bool spte_has_volatile_bits(u64 spte)
-{
- if (!is_shadow_present_pte(spte))
- return false;
-
- /*
- * Always atomically update spte if it can be updated
- * out of mmu-lock, it can ensure dirty bit is not lost,
- * also, it can help us to get a stable is_writable_pte()
- * to ensure tlb flush is not missed.
- */
- if (!is_writable_pte(spte) && is_mmu_writable_spte(spte))
- return true;
-
- if (is_access_track_spte(spte))
- return true;
-
- if (spte_ad_enabled(spte)) {
- if (!(spte & shadow_accessed_mask) ||
- (is_writable_pte(spte) && !(spte & shadow_dirty_mask)))
- return true;
- }
-
- return false;
-}
-
/* Rules for using mmu_spte_set:
* Set the sptep from nonpresent to present.
* Note: the sptep being assigned *must* be either not present
@@ -590,7 +564,8 @@ static int mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
u64 old_spte = *sptep;
int level = sptep_to_sp(sptep)->role.level;
- if (!spte_has_volatile_bits(old_spte))
+ if (!is_shadow_present_pte(old_spte) ||
+ !spte_has_volatile_bits(old_spte))
__update_clear_spte_fast(sptep, 0ull);
else
old_spte = __update_clear_spte_slow(sptep, 0ull);
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 3d611f07eee8..800b857b3a53 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -90,6 +90,34 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
E820_TYPE_RAM);
}
+/*
+ * Returns true if the SPTE has bits that may be set without holding mmu_lock.
+ * The caller is responsible for checking if the SPTE is shadow-present, and
+ * for determining whether or not the caller cares about non-leaf SPTEs.
+ */
+bool spte_has_volatile_bits(u64 spte)
+{
+ /*
+ * Always atomically update spte if it can be updated
+ * out of mmu-lock, it can ensure dirty bit is not lost,
+ * also, it can help us to get a stable is_writable_pte()
+ * to ensure tlb flush is not missed.
+ */
+ if (!is_writable_pte(spte) && is_mmu_writable_spte(spte))
+ return true;
+
+ if (is_access_track_spte(spte))
+ return true;
+
+ if (spte_ad_enabled(spte)) {
+ if (!(spte & shadow_accessed_mask) ||
+ (is_writable_pte(spte) && !(spte & shadow_dirty_mask)))
+ return true;
+ }
+
+ return false;
+}
+
bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
const struct kvm_memory_slot *slot,
unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn,
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 570699682f6d..098d7d144627 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -412,6 +412,8 @@ static inline u64 get_mmio_spte_generation(u64 spte)
return gen;
}
+bool spte_has_volatile_bits(u64 spte);
+
bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
const struct kvm_memory_slot *slot,
unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn,
--
2.36.0.rc2.479.g8af0fa9b8e-goog
