1 files changed, 123 insertions, 47 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 6941fa74eb35..0d094da49541 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -197,15 +197,63 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
 
-static void mark_mmio_spte(u64 *sptep, u64 gfn, unsigned access)
+/*
+ * spte bits of bit 3 ~ bit 11 are used as low 9 bits of generation number,
+ * the bits of bits 52 ~ bit 61 are used as high 10 bits of generation
+ * number.
+ */
+#define MMIO_SPTE_GEN_LOW_SHIFT		3
+#define MMIO_SPTE_GEN_HIGH_SHIFT	52
+
+#define MMIO_GEN_SHIFT			19
+#define MMIO_GEN_LOW_SHIFT		9
+#define MMIO_GEN_LOW_MASK		((1 << MMIO_GEN_LOW_SHIFT) - 1)
+#define MMIO_GEN_MASK			((1 << MMIO_GEN_SHIFT) - 1)
+#define MMIO_MAX_GEN			((1 << MMIO_GEN_SHIFT) - 1)
+
+static u64 generation_mmio_spte_mask(unsigned int gen)
 {
-	struct kvm_mmu_page *sp =  page_header(__pa(sptep));
+	u64 mask;
+
+	WARN_ON(gen > MMIO_MAX_GEN);
+
+	mask = (gen & MMIO_GEN_LOW_MASK) << MMIO_SPTE_GEN_LOW_SHIFT;
+	mask |= ((u64)gen >> MMIO_GEN_LOW_SHIFT) << MMIO_SPTE_GEN_HIGH_SHIFT;
+	return mask;
+}
+
+static unsigned int get_mmio_spte_generation(u64 spte)
+{
+	unsigned int gen;
+
+	spte &= ~shadow_mmio_mask;
+
+	gen = (spte >> MMIO_SPTE_GEN_LOW_SHIFT) & MMIO_GEN_LOW_MASK;
+	gen |= (spte >> MMIO_SPTE_GEN_HIGH_SHIFT) << MMIO_GEN_LOW_SHIFT;
+	return gen;
+}
+
+static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
+{
+	/*
+	 * Init kvm generation close to MMIO_MAX_GEN to easily test the
+	 * code of handling generation number wrap-around.
+	 */
+	return (kvm_memslots(kvm)->generation +
+		      MMIO_MAX_GEN - 150) & MMIO_GEN_MASK;
+}
+
+static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn,
+			   unsigned access)
+{
+	unsigned int gen = kvm_current_mmio_generation(kvm);
+	u64 mask = generation_mmio_spte_mask(gen);
 
 	access &= ACC_WRITE_MASK | ACC_USER_MASK;
+	mask |= shadow_mmio_mask | access | gfn << PAGE_SHIFT;
 
-	sp->mmio_cached = true;
-	trace_mark_mmio_spte(sptep, gfn, access);
-	mmu_spte_set(sptep, shadow_mmio_mask | access | gfn << PAGE_SHIFT);
+	trace_mark_mmio_spte(sptep, gfn, access, gen);
+	mmu_spte_set(sptep, mask);
 }
 
 static bool is_mmio_spte(u64 spte)
@@ -215,24 +263,38 @@ static bool is_mmio_spte(u64 spte)
 
 static gfn_t get_mmio_spte_gfn(u64 spte)
 {
-	return (spte & ~shadow_mmio_mask) >> PAGE_SHIFT;
+	u64 mask = generation_mmio_spte_mask(MMIO_MAX_GEN) | shadow_mmio_mask;
+	return (spte & ~mask) >> PAGE_SHIFT;
 }
 
 static unsigned get_mmio_spte_access(u64 spte)
 {
-	return (spte & ~shadow_mmio_mask) & ~PAGE_MASK;
+	u64 mask = generation_mmio_spte_mask(MMIO_MAX_GEN) | shadow_mmio_mask;
+	return (spte & ~mask) & ~PAGE_MASK;
 }
 
-static bool set_mmio_spte(u64 *sptep, gfn_t gfn, pfn_t pfn, unsigned access)
+static bool set_mmio_spte(struct kvm *kvm, u64 *sptep, gfn_t gfn,
+			  pfn_t pfn, unsigned access)
 {
 	if (unlikely(is_noslot_pfn(pfn))) {
-		mark_mmio_spte(sptep, gfn, access);
+		mark_mmio_spte(kvm, sptep, gfn, access);
 		return true;
 	}
 
 	return false;
 }
 
+static bool check_mmio_spte(struct kvm *kvm, u64 spte)
+{
+	unsigned int kvm_gen, spte_gen;
+
+	kvm_gen = kvm_current_mmio_generation(kvm);
+	spte_gen = get_mmio_spte_generation(spte);
+
+	trace_check_mmio_spte(spte, kvm_gen, spte_gen);
+	return likely(kvm_gen == spte_gen);
+}
+
 static inline u64 rsvd_bits(int s, int e)
 {
 	return ((1ULL << (e - s + 1)) - 1) << s;
@@ -404,9 +466,20 @@ static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
 /*
  * The idea using the light way get the spte on x86_32 guest is from
  * gup_get_pte(arch/x86/mm/gup.c).
- * The difference is we can not catch the spte tlb flush if we leave
- * guest mode, so we emulate it by increase clear_spte_count when spte
- * is cleared.
+ *
+ * An spte tlb flush may be pending, because kvm_set_pte_rmapp
+ * coalesces them and we are running out of the MMU lock.  Therefore
+ * we need to protect against in-progress updates of the spte.
+ *
+ * Reading the spte while an update is in progress may get the old value
+ * for the high part of the spte.  The race is fine for a present->non-present
+ * change (because the high part of the spte is ignored for non-present spte),
+ * but for a present->present change we must reread the spte.
+ *
+ * All such changes are done in two steps (present->non-present and
+ * non-present->present), hence it is enough to count the number of
+ * present->non-present updates: if it changed while reading the spte,
+ * we might have hit the race.  This is done using clear_spte_count.
  */
 static u64 __get_spte_lockless(u64 *sptep)
 {
@@ -2364,7 +2437,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	u64 spte;
 	int ret = 0;
 
-	if (set_mmio_spte(sptep, gfn, pfn, pte_access))
+	if (set_mmio_spte(vcpu->kvm, sptep, gfn, pfn, pte_access))
 		return 0;
 
 	spte = PT_PRESENT_MASK;
@@ -3184,17 +3257,12 @@ static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr)
 	return spte;
 }
 
-/*
- * If it is a real mmio page fault, return 1 and emulat the instruction
- * directly, return 0 to let CPU fault again on the address, -1 is
- * returned if bug is detected.
- */
 int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 {
 	u64 spte;
 
 	if (quickly_check_mmio_pf(vcpu, addr, direct))
-		return 1;
+		return RET_MMIO_PF_EMULATE;
 
 	spte = walk_shadow_page_get_mmio_spte(vcpu, addr);
 
@@ -3202,12 +3270,15 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 		gfn_t gfn = get_mmio_spte_gfn(spte);
 		unsigned access = get_mmio_spte_access(spte);
 
+		if (!check_mmio_spte(vcpu->kvm, spte))
+			return RET_MMIO_PF_INVALID;
+
 		if (direct)
 			addr = 0;
 
 		trace_handle_mmio_page_fault(addr, gfn, access);
 		vcpu_cache_mmio_info(vcpu, addr, gfn, access);
-		return 1;
+		return RET_MMIO_PF_EMULATE;
 	}
 
 	/*
@@ -3215,13 +3286,13 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 	 * it's a BUG if the gfn is not a mmio page.
 	 */
 	if (direct && !check_direct_spte_mmio_pf(spte))
-		return -1;
+		return RET_MMIO_PF_BUG;
 
 	/*
 	 * If the page table is zapped by other cpus, let CPU fault again on
 	 * the address.
 	 */
-	return 0;
+	return RET_MMIO_PF_RETRY;
 }
 EXPORT_SYMBOL_GPL(handle_mmio_page_fault_common);
 
@@ -3231,7 +3302,7 @@ static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr,
 	int ret;
 
 	ret = handle_mmio_page_fault_common(vcpu, addr, direct);
-	WARN_ON(ret < 0);
+	WARN_ON(ret == RET_MMIO_PF_BUG);
 	return ret;
 }
 
@@ -3243,8 +3314,12 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 
 	pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);
 
-	if (unlikely(error_code & PFERR_RSVD_MASK))
-		return handle_mmio_page_fault(vcpu, gva, error_code, true);
+	if (unlikely(error_code & PFERR_RSVD_MASK)) {
+		r = handle_mmio_page_fault(vcpu, gva, error_code, true);
+
+		if (likely(r != RET_MMIO_PF_INVALID))
+			return r;
+	}
 
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
@@ -3320,8 +3395,12 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 	ASSERT(vcpu);
 	ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
 
-	if (unlikely(error_code & PFERR_RSVD_MASK))
-		return handle_mmio_page_fault(vcpu, gpa, error_code, true);
+	if (unlikely(error_code & PFERR_RSVD_MASK)) {
+		r = handle_mmio_page_fault(vcpu, gpa, error_code, true);
+
+		if (likely(r != RET_MMIO_PF_INVALID))
+			return r;
+	}
 
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
@@ -3427,8 +3506,8 @@ static inline void protect_clean_gpte(unsigned *access, unsigned gpte)
 	*access &= mask;
 }
 
-static bool sync_mmio_spte(u64 *sptep, gfn_t gfn, unsigned access,
-			   int *nr_present)
+static bool sync_mmio_spte(struct kvm *kvm, u64 *sptep, gfn_t gfn,
+			   unsigned access, int *nr_present)
 {
 	if (unlikely(is_mmio_spte(*sptep))) {
 		if (gfn != get_mmio_spte_gfn(*sptep)) {
@@ -3437,7 +3516,7 @@ static bool sync_mmio_spte(u64 *sptep, gfn_t gfn, unsigned access,
 		}
 
 		(*nr_present)++;
-		mark_mmio_spte(sptep, gfn, access);
+		mark_mmio_spte(kvm, sptep, gfn, access);
 		return true;
 	}
 
@@ -4294,27 +4373,24 @@ void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm)
 	spin_unlock(&kvm->mmu_lock);
 }
 
-void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
+static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
 {
-	struct kvm_mmu_page *sp, *node;
-	LIST_HEAD(invalid_list);
-
-	spin_lock(&kvm->mmu_lock);
-restart:
-	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
-		if (!sp->mmio_cached)
-			continue;
-		if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
-			goto restart;
-	}
-
-	kvm_mmu_commit_zap_page(kvm, &invalid_list);
-	spin_unlock(&kvm->mmu_lock);
+	return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
 }
 
-static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
+void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
 {
-	return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
+	/*
+	 * The very rare case: if the generation-number is round,
+	 * zap all shadow pages.
+	 *
+	 * The max value is MMIO_MAX_GEN - 1 since it is not called
+	 * when mark memslot invalid.
+	 */
+	if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1))) {
+		printk_ratelimited(KERN_INFO "kvm: zapping shadow pages for mmio generation wraparound\n");
+		kvm_mmu_invalidate_zap_all_pages(kvm);
+	}
 }
 
 static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)