diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index 869abcc..2908941 100644
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -210,6 +210,24 @@
     A bitmap indicating which sptes in spt point (directly or indirectly) at
     pages that may be unsynchronized.  Used to quickly locate all unsychronized
     pages reachable from a given page.
+  mmu_valid_gen:
+    Generation number of the page.  It is compared with kvm->arch.mmu_valid_gen
+    during hash table lookup, and used to skip invalidated shadow pages (see
+    "Zapping all pages" below.)
+  clear_spte_count:
+    Only present on 32-bit hosts, where a 64-bit spte cannot be written
+    atomically.  The reader uses this while running out of the MMU lock
+    to detect in-progress updates and retry them until the writer has
+    finished the write.
+  write_flooding_count:
+    A guest may write to a page table many times, causing a lot of
+    emulations if the page needs to be write-protected (see "Synchronized
+    and unsynchronized pages" below).  Leaf pages can be unsynchronized
+    so that they do not trigger frequent emulation, but this is not
+    possible for non-leafs.  This field counts the number of emulations
+    since the last time the page table was actually used; if emulation
+    is triggered too frequently on this page, KVM will unmap the page
+    to avoid emulation in the future.
 
 Reverse map
 ===========
@@ -258,14 +276,26 @@
 
 Handling a page fault is performed as follows:
 
+ - if the RSV bit of the error code is set, the page fault is caused by guest
+   accessing MMIO and cached MMIO information is available.
+   - walk shadow page table
+   - check for valid generation number in the spte (see "Fast invalidation of
+     MMIO sptes" below)
+   - cache the information to vcpu->arch.mmio_gva, vcpu->arch.access and
+     vcpu->arch.mmio_gfn, and call the emulator
+ - If both P bit and R/W bit of error code are set, this could possibly
+   be handled as a "fast page fault" (fixed without taking the MMU lock).  See
+   the description in Documentation/virtual/kvm/locking.txt.
  - if needed, walk the guest page tables to determine the guest translation
    (gva->gpa or ngpa->gpa)
    - if permissions are insufficient, reflect the fault back to the guest
  - determine the host page
-   - if this is an mmio request, there is no host page; call the emulator
-     to emulate the instruction instead
+   - if this is an mmio request, there is no host page; cache the info to
+     vcpu->arch.mmio_gva, vcpu->arch.access and vcpu->arch.mmio_gfn
  - walk the shadow page table to find the spte for the translation,
    instantiating missing intermediate page tables as necessary
+   - If this is an mmio request, cache the mmio info to the spte and set some
+     reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask)
  - try to unsynchronize the page
    - if successful, we can let the guest continue and modify the gpte
  - emulate the instruction
@@ -351,6 +381,51 @@
 a large spte.  The frames at the end of an unaligned memory slot have
 artificially inflated ->write_counts so they can never be instantiated.
 
+Zapping all pages (page generation count)
+=========================================
+
+For the large memory guests, walking and zapping all pages is really slow
+(because there are a lot of pages), and also blocks memory accesses of
+all VCPUs because it needs to hold the MMU lock.
+
+To make it be more scalable, kvm maintains a global generation number
+which is stored in kvm->arch.mmu_valid_gen.  Every shadow page stores
+the current global generation-number into sp->mmu_valid_gen when it
+is created.  Pages with a mismatching generation number are "obsolete".
+
+When KVM need zap all shadow pages sptes, it just simply increases the global
+generation-number then reload root shadow pages on all vcpus.  As the VCPUs
+create new shadow page tables, the old pages are not used because of the
+mismatching generation number.
+
+KVM then walks through all pages and zaps obsolete pages.  While the zap
+operation needs to take the MMU lock, the lock can be released periodically
+so that the VCPUs can make progress.
+
+Fast invalidation of MMIO sptes
+===============================
+
+As mentioned in "Reaction to events" above, kvm will cache MMIO
+information in leaf sptes.  When a new memslot is added or an existing
+memslot is changed, this information may become stale and needs to be
+invalidated.  This also needs to hold the MMU lock while walking all
+shadow pages, and is made more scalable with a similar technique.
+
+MMIO sptes have a few spare bits, which are used to store a
+generation number.  The global generation number is stored in
+kvm_memslots(kvm)->generation, and increased whenever guest memory info
+changes.  This generation number is distinct from the one described in
+the previous section.
+
+When KVM finds an MMIO spte, it checks the generation number of the spte.
+If the generation number of the spte does not equal the global generation
+number, it will ignore the cached MMIO information and handle the page
+fault through the slow path.
+
+Since only 19 bits are used to store generation-number on mmio spte, all
+pages are zapped when there is an overflow.
+
+
 Further reading
 ===============
 
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1f98c1b..280e327 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -222,15 +222,22 @@
 	int root_count;          /* Currently serving as active root */
 	unsigned int unsync_children;
 	unsigned long parent_ptes;	/* Reverse mapping for parent_pte */
+
+	/* The page is obsolete if mmu_valid_gen != kvm->arch.mmu_valid_gen.  */
 	unsigned long mmu_valid_gen;
+
 	DECLARE_BITMAP(unsync_child_bitmap, 512);
 
 #ifdef CONFIG_X86_32
+	/*
+	 * Used out of the mmu-lock to avoid reading spte values while an
+	 * update is in progress; see the comments in __get_spte_lockless().
+	 */
 	int clear_spte_count;
 #endif
 
+	/* Number of writes since the last time traversal visited this page.  */
 	int write_flooding_count;
-	bool mmio_cached;
 };
 
 struct kvm_pio_request {
@@ -773,7 +780,7 @@
 				     struct kvm_memory_slot *slot,
 				     gfn_t gfn_offset, unsigned long mask);
 void kvm_mmu_zap_all(struct kvm *kvm);
-void kvm_mmu_zap_mmio_sptes(struct kvm *kvm);
+void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm);
 unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
 void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);
 
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9d75193..9f4bea8 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -405,17 +405,17 @@
 	return highest_irr;
 }
 
-static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
-			      int vector, int level, int trig_mode,
-			      unsigned long *dest_map);
+static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
+			     int vector, int level, int trig_mode,
+			     unsigned long *dest_map);
 
-void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
-		      unsigned long *dest_map)
+int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
+		unsigned long *dest_map)
 {
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
-	__apic_accept_irq(apic, irq->delivery_mode, irq->vector,
-			  irq->level, irq->trig_mode, dest_map);
+	return __apic_accept_irq(apic, irq->delivery_mode, irq->vector,
+			irq->level, irq->trig_mode, dest_map);
 }
 
 static int pv_eoi_put_user(struct kvm_vcpu *vcpu, u8 val)
@@ -608,8 +608,7 @@
 	*r = -1;
 
 	if (irq->shorthand == APIC_DEST_SELF) {
-		kvm_apic_set_irq(src->vcpu, irq, dest_map);
-		*r = 1;
+		*r = kvm_apic_set_irq(src->vcpu, irq, dest_map);
 		return true;
 	}
 
@@ -654,8 +653,7 @@
 			continue;
 		if (*r < 0)
 			*r = 0;
-		kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
-		*r += 1;
+		*r += kvm_apic_set_irq(dst[i]->vcpu, irq, dest_map);
 	}
 
 	ret = true;
@@ -664,11 +662,15 @@
 	return ret;
 }
 
-/* Set an IRQ pending in the lapic. */
-static void __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
-			      int vector, int level, int trig_mode,
-			      unsigned long *dest_map)
+/*
+ * Add a pending IRQ into lapic.
+ * Return 1 if successfully added and 0 if discarded.
+ */
+static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
+			     int vector, int level, int trig_mode,
+			     unsigned long *dest_map)
 {
+	int result = 0;
 	struct kvm_vcpu *vcpu = apic->vcpu;
 
 	switch (delivery_mode) {
@@ -682,10 +684,13 @@
 		if (dest_map)
 			__set_bit(vcpu->vcpu_id, dest_map);
 
-		if (kvm_x86_ops->deliver_posted_interrupt)
+		if (kvm_x86_ops->deliver_posted_interrupt) {
+			result = 1;
 			kvm_x86_ops->deliver_posted_interrupt(vcpu, vector);
-		else {
-			if (apic_test_and_set_irr(vector, apic)) {
+		} else {
+			result = !apic_test_and_set_irr(vector, apic);
+
+			if (!result) {
 				if (trig_mode)
 					apic_debug("level trig mode repeatedly "
 						"for vector %d", vector);
@@ -697,7 +702,7 @@
 		}
 out:
 		trace_kvm_apic_accept_irq(vcpu->vcpu_id, delivery_mode,
-					  trig_mode, vector, false);
+				trig_mode, vector, !result);
 		break;
 
 	case APIC_DM_REMRD:
@@ -709,12 +714,14 @@
 		break;
 
 	case APIC_DM_NMI:
+		result = 1;
 		kvm_inject_nmi(vcpu);
 		kvm_vcpu_kick(vcpu);
 		break;
 
 	case APIC_DM_INIT:
 		if (!trig_mode || level) {
+			result = 1;
 			/* assumes that there are only KVM_APIC_INIT/SIPI */
 			apic->pending_events = (1UL << KVM_APIC_INIT);
 			/* make sure pending_events is visible before sending
@@ -731,6 +738,7 @@
 	case APIC_DM_STARTUP:
 		apic_debug("SIPI to vcpu %d vector 0x%02x\n",
 			   vcpu->vcpu_id, vector);
+		result = 1;
 		apic->sipi_vector = vector;
 		/* make sure sipi_vector is visible for the receiver */
 		smp_wmb();
@@ -752,6 +760,7 @@
 		       delivery_mode);
 		break;
 	}
+	return result;
 }
 
 int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2)
@@ -1461,7 +1470,7 @@
 	return 0;
 }
 
-void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
+int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
 {
 	u32 reg = kvm_apic_get_reg(apic, lvt_type);
 	int vector, mode, trig_mode;
@@ -1470,8 +1479,10 @@
 		vector = reg & APIC_VECTOR_MASK;
 		mode = reg & APIC_MODE_MASK;
 		trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;
-		__apic_accept_irq(apic, mode, vector, 1, trig_mode, NULL);
+		return __apic_accept_irq(apic, mode, vector, 1, trig_mode,
+					NULL);
 	}
+	return 0;
 }
 
 void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 61a73a0..c730ac9 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -57,9 +57,9 @@
 void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
 int kvm_apic_match_physical_addr(struct kvm_lapic *apic, u16 dest);
 int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda);
-void kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
-		      unsigned long *dest_map);
-void kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
+int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
+		unsigned long *dest_map);
+int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
 
 bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 		struct kvm_lapic_irq *irq, int *r, unsigned long *dest_map);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 6941fa7..0d094da 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -197,15 +197,63 @@
 }
 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 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 @@
 /*
  * 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 @@
 	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 @@
 	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 @@
 		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 @@
 	 * 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 @@
 	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 @@
 
 	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 @@
 	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 @@
 	*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 @@
 		}
 
 		(*nr_present)++;
-		mark_mmio_spte(sptep, gfn, access);
+		mark_mmio_spte(kvm, sptep, gfn, access);
 		return true;
 	}
 
@@ -4294,29 +4373,26 @@
 	spin_unlock(&kvm->mmu_lock);
 }
 
-void kvm_mmu_zap_mmio_sptes(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);
-}
-
 static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
 {
 	return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
 }
 
+void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
+{
+	/*
+	 * 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)
 {
 	struct kvm *kvm;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 922bfae..5b59c57 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -52,6 +52,23 @@
 
 int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4]);
 void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask);
+
+/*
+ * Return values of handle_mmio_page_fault_common:
+ * RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
+ *			directly.
+ * RET_MMIO_PF_INVALID: invalid spte is detected then let the real page
+ *			fault path update the mmio spte.
+ * RET_MMIO_PF_RETRY: let CPU fault again on the address.
+ * RET_MMIO_PF_BUG: bug is detected.
+ */
+enum {
+	RET_MMIO_PF_EMULATE = 1,
+	RET_MMIO_PF_INVALID = 2,
+	RET_MMIO_PF_RETRY = 0,
+	RET_MMIO_PF_BUG = -1
+};
+
 int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct);
 int kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
 
diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
index eb444dd..9d2e0ff 100644
--- a/arch/x86/kvm/mmutrace.h
+++ b/arch/x86/kvm/mmutrace.h
@@ -199,23 +199,25 @@
 
 TRACE_EVENT(
 	mark_mmio_spte,
-	TP_PROTO(u64 *sptep, gfn_t gfn, unsigned access),
-	TP_ARGS(sptep, gfn, access),
+	TP_PROTO(u64 *sptep, gfn_t gfn, unsigned access, unsigned int gen),
+	TP_ARGS(sptep, gfn, access, gen),
 
 	TP_STRUCT__entry(
 		__field(void *, sptep)
 		__field(gfn_t, gfn)
 		__field(unsigned, access)
+		__field(unsigned int, gen)
 	),
 
 	TP_fast_assign(
 		__entry->sptep = sptep;
 		__entry->gfn = gfn;
 		__entry->access = access;
+		__entry->gen = gen;
 	),
 
-	TP_printk("sptep:%p gfn %llx access %x", __entry->sptep, __entry->gfn,
-		  __entry->access)
+	TP_printk("sptep:%p gfn %llx access %x gen %x", __entry->sptep,
+		  __entry->gfn, __entry->access, __entry->gen)
 );
 
 TRACE_EVENT(
@@ -296,6 +298,30 @@
 		  __entry->mmu_valid_gen, __entry->mmu_used_pages
 	)
 );
+
+
+TRACE_EVENT(
+	check_mmio_spte,
+	TP_PROTO(u64 spte, unsigned int kvm_gen, unsigned int spte_gen),
+	TP_ARGS(spte, kvm_gen, spte_gen),
+
+	TP_STRUCT__entry(
+		__field(unsigned int, kvm_gen)
+		__field(unsigned int, spte_gen)
+		__field(u64, spte)
+	),
+
+	TP_fast_assign(
+		__entry->kvm_gen = kvm_gen;
+		__entry->spte_gen = spte_gen;
+		__entry->spte = spte;
+	),
+
+	TP_printk("spte %llx kvm_gen %x spte-gen %x valid %d", __entry->spte,
+		  __entry->kvm_gen, __entry->spte_gen,
+		  __entry->kvm_gen == __entry->spte_gen
+	)
+);
 #endif /* _TRACE_KVMMMU_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index da20860..7769699 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -552,9 +552,12 @@
 
 	pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
 
-	if (unlikely(error_code & PFERR_RSVD_MASK))
-		return handle_mmio_page_fault(vcpu, addr, error_code,
+	if (unlikely(error_code & PFERR_RSVD_MASK)) {
+		r = handle_mmio_page_fault(vcpu, addr, error_code,
 					      mmu_is_nested(vcpu));
+		if (likely(r != RET_MMIO_PF_INVALID))
+			return r;
+	};
 
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
@@ -792,7 +795,8 @@
 		pte_access &= gpte_access(vcpu, gpte);
 		protect_clean_gpte(&pte_access, gpte);
 
-		if (sync_mmio_spte(&sp->spt[i], gfn, pte_access, &nr_present))
+		if (sync_mmio_spte(vcpu->kvm, &sp->spt[i], gfn, pte_access,
+		      &nr_present))
 			continue;
 
 		if (gfn != sp->gfns[i]) {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a14a6ea..c0bc803 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1026,7 +1026,10 @@
 		g_tsc_offset = svm->vmcb->control.tsc_offset -
 			       svm->nested.hsave->control.tsc_offset;
 		svm->nested.hsave->control.tsc_offset = offset;
-	}
+	} else
+		trace_kvm_write_tsc_offset(vcpu->vcpu_id,
+					   svm->vmcb->control.tsc_offset,
+					   offset);
 
 	svm->vmcb->control.tsc_offset = offset + g_tsc_offset;
 
@@ -1044,6 +1047,11 @@
 	svm->vmcb->control.tsc_offset += adjustment;
 	if (is_guest_mode(vcpu))
 		svm->nested.hsave->control.tsc_offset += adjustment;
+	else
+		trace_kvm_write_tsc_offset(vcpu->vcpu_id,
+				     svm->vmcb->control.tsc_offset - adjustment,
+				     svm->vmcb->control.tsc_offset);
+
 	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 }
 
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index fe5e00e..545245d 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -756,6 +756,27 @@
 		  __entry->gpa_match ? "GPA" : "GVA")
 );
 
+TRACE_EVENT(kvm_write_tsc_offset,
+	TP_PROTO(unsigned int vcpu_id, __u64 previous_tsc_offset,
+		 __u64 next_tsc_offset),
+	TP_ARGS(vcpu_id, previous_tsc_offset, next_tsc_offset),
+
+	TP_STRUCT__entry(
+		__field( unsigned int,	vcpu_id				)
+		__field(	__u64,	previous_tsc_offset		)
+		__field(	__u64,	next_tsc_offset			)
+	),
+
+	TP_fast_assign(
+		__entry->vcpu_id		= vcpu_id;
+		__entry->previous_tsc_offset	= previous_tsc_offset;
+		__entry->next_tsc_offset	= next_tsc_offset;
+	),
+
+	TP_printk("vcpu=%u prev=%llu next=%llu", __entry->vcpu_id,
+		  __entry->previous_tsc_offset, __entry->next_tsc_offset)
+);
+
 #ifdef CONFIG_X86_64
 
 #define host_clocks					\
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 260a919..036e863 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2096,6 +2096,8 @@
 			(nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ?
 			 vmcs12->tsc_offset : 0));
 	} else {
+		trace_kvm_write_tsc_offset(vcpu->vcpu_id,
+					   vmcs_read64(TSC_OFFSET), offset);
 		vmcs_write64(TSC_OFFSET, offset);
 	}
 }
@@ -2103,11 +2105,14 @@
 static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool host)
 {
 	u64 offset = vmcs_read64(TSC_OFFSET);
+
 	vmcs_write64(TSC_OFFSET, offset + adjustment);
 	if (is_guest_mode(vcpu)) {
 		/* Even when running L2, the adjustment needs to apply to L1 */
 		to_vmx(vcpu)->nested.vmcs01_tsc_offset += adjustment;
-	}
+	} else
+		trace_kvm_write_tsc_offset(vcpu->vcpu_id, offset,
+					   offset + adjustment);
 }
 
 static u64 vmx_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
@@ -4176,10 +4181,10 @@
 	/*
 	 * EPT Misconfigurations can be generated if the value of bits 2:0
 	 * of an EPT paging-structure entry is 110b (write/execute).
-	 * Also, magic bits (0xffull << 49) is set to quickly identify mmio
+	 * Also, magic bits (0x3ull << 62) is set to quickly identify mmio
 	 * spte.
 	 */
-	kvm_mmu_set_mmio_spte_mask(0xffull << 49 | 0x6ull);
+	kvm_mmu_set_mmio_spte_mask((0x3ull << 62) | 0x6ull);
 }
 
 /*
@@ -5366,10 +5371,14 @@
 	gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
 
 	ret = handle_mmio_page_fault_common(vcpu, gpa, true);
-	if (likely(ret == 1))
+	if (likely(ret == RET_MMIO_PF_EMULATE))
 		return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==
 					      EMULATE_DONE;
-	if (unlikely(!ret))
+
+	if (unlikely(ret == RET_MMIO_PF_INVALID))
+		return kvm_mmu_page_fault(vcpu, gpa, 0, NULL, 0);
+
+	if (unlikely(ret == RET_MMIO_PF_RETRY))
 		return 1;
 
 	/* It is the real ept misconfig */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 737c804..7d71c0f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5280,7 +5280,13 @@
 	 * Set the reserved bits and the present bit of an paging-structure
 	 * entry to generate page fault with PFER.RSV = 1.
 	 */
-	mask = ((1ull << (62 - maxphyaddr + 1)) - 1) << maxphyaddr;
+	 /* Mask the reserved physical address bits. */
+	mask = ((1ull << (51 - maxphyaddr + 1)) - 1) << maxphyaddr;
+
+	/* Bit 62 is always reserved for 32bit host. */
+	mask |= 0x3ull << 62;
+
+	/* Set the present bit. */
 	mask |= 1ull;
 
 #ifdef CONFIG_X86_64
@@ -7078,8 +7084,7 @@
 	 * If memory slot is created, or moved, we need to clear all
 	 * mmio sptes.
 	 */
-	if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE))
-		kvm_mmu_zap_mmio_sptes(kvm);
+	kvm_mmu_invalidate_mmio_sptes(kvm);
 }
 
 void kvm_arch_flush_shadow_all(struct kvm *kvm)
@@ -7298,3 +7303,4 @@
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_invlpga);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_skinit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_intercepts);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_write_tsc_offset);
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index ef1817b..e2e6b44 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -91,8 +91,7 @@
 		if (!kvm_is_dm_lowest_prio(irq)) {
 			if (r < 0)
 				r = 0;
-			kvm_apic_set_irq(vcpu, irq, dest_map);
-			r++;
+			r += kvm_apic_set_irq(vcpu, irq, dest_map);
 		} else if (kvm_lapic_enabled(vcpu)) {
 			if (!lowest)
 				lowest = vcpu;
@@ -101,10 +100,8 @@
 		}
 	}
 
-	if (lowest) {
-		kvm_apic_set_irq(lowest, irq, dest_map);
-		r = 1;
-	}
+	if (lowest)
+		r = kvm_apic_set_irq(lowest, irq, dest_map);
 
 	return r;
 }