diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e209078..043e29e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -83,11 +83,14 @@
 #define KVM_NR_FIXED_MTRR_REGION 88
 #define KVM_NR_VAR_MTRR 8
 
+#define ASYNC_PF_PER_VCPU 64
+
 extern spinlock_t kvm_lock;
 extern struct list_head vm_list;
 
 struct kvm_vcpu;
 struct kvm;
+struct kvm_async_pf;
 
 enum kvm_reg {
 	VCPU_REGS_RAX = 0,
@@ -412,6 +415,11 @@ struct kvm_vcpu_arch {
 	u64 hv_vapic;
 
 	cpumask_var_t wbinvd_dirty_mask;
+
+	struct {
+		bool halted;
+		gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];
+	} apf;
 };
 
 struct kvm_arch {
@@ -585,6 +593,10 @@ struct kvm_x86_ops {
 	const struct trace_print_flags *exit_reasons_str;
 };
 
+struct kvm_arch_async_pf {
+	gfn_t gfn;
+};
+
 extern struct kvm_x86_ops *kvm_x86_ops;
 
 int kvm_mmu_module_init(void);
@@ -823,4 +835,10 @@ void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
 
 bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);
 
+void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
+				     struct kvm_async_pf *work);
+void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
+				 struct kvm_async_pf *work);
+extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
+
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index ddc131f..50f6364 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -28,6 +28,7 @@ config KVM
 	select HAVE_KVM_IRQCHIP
 	select HAVE_KVM_EVENTFD
 	select KVM_APIC_ARCHITECTURE
+	select KVM_ASYNC_PF
 	select USER_RETURN_NOTIFIER
 	select KVM_MMIO
 	---help---
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 31a7035..c53bf19 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -9,6 +9,7 @@ kvm-y			+= $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
 				coalesced_mmio.o irq_comm.o eventfd.o \
 				assigned-dev.o)
 kvm-$(CONFIG_IOMMU_API)	+= $(addprefix ../../../virt/kvm/, iommu.o)
+kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(addprefix ../../../virt/kvm/, async_pf.o)
 
 kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
 			   i8254.o timer.o
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 908ea54..f01e89a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -18,9 +18,11 @@
  *
  */
 
+#include "irq.h"
 #include "mmu.h"
 #include "x86.h"
 #include "kvm_cache_regs.h"
+#include "x86.h"
 
 #include <linux/kvm_host.h>
 #include <linux/types.h>
@@ -2585,6 +2587,50 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 			     error_code & PFERR_WRITE_MASK, gfn);
 }
 
+int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn)
+{
+	struct kvm_arch_async_pf arch;
+	arch.gfn = gfn;
+
+	return kvm_setup_async_pf(vcpu, gva, gfn, &arch);
+}
+
+static bool can_do_async_pf(struct kvm_vcpu *vcpu)
+{
+	if (unlikely(!irqchip_in_kernel(vcpu->kvm) ||
+		     kvm_event_needs_reinjection(vcpu)))
+		return false;
+
+	return kvm_x86_ops->interrupt_allowed(vcpu);
+}
+
+static bool try_async_pf(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
+			 pfn_t *pfn)
+{
+	bool async;
+
+	*pfn = gfn_to_pfn_async(vcpu->kvm, gfn, &async);
+
+	if (!async)
+		return false; /* *pfn has correct page already */
+
+	put_page(pfn_to_page(*pfn));
+
+	if (can_do_async_pf(vcpu)) {
+		trace_kvm_try_async_get_page(async, *pfn);
+		if (kvm_find_async_pf_gfn(vcpu, gfn)) {
+			trace_kvm_async_pf_doublefault(gva, gfn);
+			kvm_make_request(KVM_REQ_APF_HALT, vcpu);
+			return true;
+		} else if (kvm_arch_setup_async_pf(vcpu, gva, gfn))
+			return true;
+	}
+
+	*pfn = gfn_to_pfn(vcpu->kvm, gfn);
+	
+	return false;
+}
+
 static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
 				u32 error_code)
 {
@@ -2607,7 +2653,11 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa,
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
-	pfn = gfn_to_pfn(vcpu->kvm, gfn);
+
+	if (try_async_pf(vcpu, gfn, gpa, &pfn))
+		return 0;
+
+	/* mmio */
 	if (is_error_pfn(pfn))
 		return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
 	spin_lock(&vcpu->kvm->mmu_lock);
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index cd7a833..c45376d 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -568,7 +568,9 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
-	pfn = gfn_to_pfn(vcpu->kvm, walker.gfn);
+
+	if (try_async_pf(vcpu, walker.gfn, addr, &pfn))
+		return 0;
 
 	/* mmio */
 	if (is_error_pfn(pfn))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7127a13..09e72fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -43,6 +43,7 @@
 #include <linux/slab.h>
 #include <linux/perf_event.h>
 #include <linux/uaccess.h>
+#include <linux/hash.h>
 #include <trace/events/kvm.h>
 
 #define CREATE_TRACE_POINTS
@@ -155,6 +156,13 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 
 u64 __read_mostly host_xcr0;
 
+static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
+{
+	int i;
+	for (i = 0; i < roundup_pow_of_two(ASYNC_PF_PER_VCPU); i++)
+		vcpu->arch.apf.gfns[i] = ~0;
+}
+
 static inline u32 bit(int bitno)
 {
 	return 1 << (bitno & 31);
@@ -5110,6 +5118,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			vcpu->fpu_active = 0;
 			kvm_x86_ops->fpu_deactivate(vcpu);
 		}
+		if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
+			/* Page is swapped out. Do synthetic halt */
+			vcpu->arch.apf.halted = true;
+			r = 1;
+			goto out;
+		}
 	}
 
 	r = kvm_mmu_reload(vcpu);
@@ -5238,7 +5252,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 
 	r = 1;
 	while (r > 0) {
-		if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE)
+		if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
+		    !vcpu->arch.apf.halted)
 			r = vcpu_enter_guest(vcpu);
 		else {
 			srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
@@ -5251,6 +5266,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 					vcpu->arch.mp_state =
 						KVM_MP_STATE_RUNNABLE;
 				case KVM_MP_STATE_RUNNABLE:
+					vcpu->arch.apf.halted = false;
 					break;
 				case KVM_MP_STATE_SIPI_RECEIVED:
 				default:
@@ -5272,6 +5288,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 			vcpu->run->exit_reason = KVM_EXIT_INTR;
 			++vcpu->stat.request_irq_exits;
 		}
+		
+		kvm_check_async_pf_completion(vcpu);
+
 		if (signal_pending(current)) {
 			r = -EINTR;
 			vcpu->run->exit_reason = KVM_EXIT_INTR;
@@ -5785,6 +5804,10 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
 
 	kvm_make_request(KVM_REQ_EVENT, vcpu);
 
+	kvm_clear_async_pf_completion_queue(vcpu);
+	kvm_async_pf_hash_reset(vcpu);
+	vcpu->arch.apf.halted = false;
+
 	return kvm_x86_ops->vcpu_reset(vcpu);
 }
 
@@ -5873,6 +5896,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 	if (!zalloc_cpumask_var(&vcpu->arch.wbinvd_dirty_mask, GFP_KERNEL))
 		goto fail_free_mce_banks;
 
+	kvm_async_pf_hash_reset(vcpu);
+
 	return 0;
 fail_free_mce_banks:
 	kfree(vcpu->arch.mce_banks);
@@ -5931,8 +5956,10 @@ static void kvm_free_vcpus(struct kvm *kvm)
 	/*
 	 * Unpin any mmu pages first.
 	 */
-	kvm_for_each_vcpu(i, vcpu, kvm)
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		kvm_clear_async_pf_completion_queue(vcpu);
 		kvm_unload_vcpu_mmu(vcpu);
+	}
 	kvm_for_each_vcpu(i, vcpu, kvm)
 		kvm_arch_vcpu_free(vcpu);
 
@@ -6043,7 +6070,9 @@ void kvm_arch_flush_shadow(struct kvm *kvm)
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 {
-	return vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE
+	return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
+		!vcpu->arch.apf.halted)
+		|| !list_empty_careful(&vcpu->async_pf.done)
 		|| vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
 		|| vcpu->arch.nmi_pending ||
 		(kvm_arch_interrupt_allowed(vcpu) &&
@@ -6102,6 +6131,83 @@ void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
 }
 EXPORT_SYMBOL_GPL(kvm_set_rflags);
 
+static inline u32 kvm_async_pf_hash_fn(gfn_t gfn)
+{
+	return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU));
+}
+
+static inline u32 kvm_async_pf_next_probe(u32 key)
+{
+	return (key + 1) & (roundup_pow_of_two(ASYNC_PF_PER_VCPU) - 1);
+}
+
+static void kvm_add_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	u32 key = kvm_async_pf_hash_fn(gfn);
+
+	while (vcpu->arch.apf.gfns[key] != ~0)
+		key = kvm_async_pf_next_probe(key);
+
+	vcpu->arch.apf.gfns[key] = gfn;
+}
+
+static u32 kvm_async_pf_gfn_slot(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	int i;
+	u32 key = kvm_async_pf_hash_fn(gfn);
+
+	for (i = 0; i < roundup_pow_of_two(ASYNC_PF_PER_VCPU) &&
+		     (vcpu->arch.apf.gfns[key] != gfn ||
+		      vcpu->arch.apf.gfns[key] == ~0); i++)
+		key = kvm_async_pf_next_probe(key);
+
+	return key;
+}
+
+bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	return vcpu->arch.apf.gfns[kvm_async_pf_gfn_slot(vcpu, gfn)] == gfn;
+}
+
+static void kvm_del_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	u32 i, j, k;
+
+	i = j = kvm_async_pf_gfn_slot(vcpu, gfn);
+	while (true) {
+		vcpu->arch.apf.gfns[i] = ~0;
+		do {
+			j = kvm_async_pf_next_probe(j);
+			if (vcpu->arch.apf.gfns[j] == ~0)
+				return;
+			k = kvm_async_pf_hash_fn(vcpu->arch.apf.gfns[j]);
+			/*
+			 * k lies cyclically in ]i,j]
+			 * |    i.k.j |
+			 * |....j i.k.| or  |.k..j i...|
+			 */
+		} while ((i <= j) ? (i < k && k <= j) : (i < k || k <= j));
+		vcpu->arch.apf.gfns[i] = vcpu->arch.apf.gfns[j];
+		i = j;
+	}
+}
+
+void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
+				     struct kvm_async_pf *work)
+{
+	trace_kvm_async_pf_not_present(work->gva);
+
+	kvm_make_request(KVM_REQ_APF_HALT, vcpu);
+	kvm_add_async_pf_gfn(vcpu, work->arch.gfn);
+}
+
+void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
+				 struct kvm_async_pf *work)
+{
+	trace_kvm_async_pf_ready(work->gva);
+	kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
+}
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0b89d00..9a9b017 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -40,6 +40,7 @@
 #define KVM_REQ_KICK               9
 #define KVM_REQ_DEACTIVATE_FPU    10
 #define KVM_REQ_EVENT             11
+#define KVM_REQ_APF_HALT          12
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID	0
 
@@ -74,6 +75,26 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 			      struct kvm_io_device *dev);
 
+#ifdef CONFIG_KVM_ASYNC_PF
+struct kvm_async_pf {
+	struct work_struct work;
+	struct list_head link;
+	struct list_head queue;
+	struct kvm_vcpu *vcpu;
+	struct mm_struct *mm;
+	gva_t gva;
+	unsigned long addr;
+	struct kvm_arch_async_pf arch;
+	struct page *page;
+	bool done;
+};
+
+void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
+void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
+int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
+		       struct kvm_arch_async_pf *arch);
+#endif
+
 struct kvm_vcpu {
 	struct kvm *kvm;
 #ifdef CONFIG_PREEMPT_NOTIFIERS
@@ -104,6 +125,15 @@ struct kvm_vcpu {
 	gpa_t mmio_phys_addr;
 #endif
 
+#ifdef CONFIG_KVM_ASYNC_PF
+	struct {
+		u32 queued;
+		struct list_head queue;
+		struct list_head done;
+		spinlock_t lock;
+	} async_pf;
+#endif
+
 	struct kvm_vcpu_arch arch;
 };
 
@@ -302,6 +332,7 @@ void kvm_set_page_accessed(struct page *page);
 
 pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr);
 pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn);
+pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async);
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
 			 struct kvm_memory_slot *slot, gfn_t gfn);
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 6dd3a51..a78a5e5 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -185,6 +185,96 @@ TRACE_EVENT(kvm_age_page,
 		  __entry->referenced ? "YOUNG" : "OLD")
 );
 
+#ifdef CONFIG_KVM_ASYNC_PF
+TRACE_EVENT(
+	kvm_try_async_get_page,
+	TP_PROTO(bool async, u64 pfn),
+	TP_ARGS(async, pfn),
+
+	TP_STRUCT__entry(
+		__field(__u64, pfn)
+		),
+
+	TP_fast_assign(
+		__entry->pfn = (!async) ? pfn : (u64)-1;
+		),
+
+	TP_printk("pfn %#llx", __entry->pfn)
+);
+
+TRACE_EVENT(
+	kvm_async_pf_not_present,
+	TP_PROTO(u64 gva),
+	TP_ARGS(gva),
+
+	TP_STRUCT__entry(
+		__field(__u64, gva)
+		),
+
+	TP_fast_assign(
+		__entry->gva = gva;
+		),
+
+	TP_printk("gva %#llx not present", __entry->gva)
+);
+
+TRACE_EVENT(
+	kvm_async_pf_ready,
+	TP_PROTO(u64 gva),
+	TP_ARGS(gva),
+
+	TP_STRUCT__entry(
+		__field(__u64, gva)
+		),
+
+	TP_fast_assign(
+		__entry->gva = gva;
+		),
+
+	TP_printk("gva %#llx ready", __entry->gva)
+);
+
+TRACE_EVENT(
+	kvm_async_pf_completed,
+	TP_PROTO(unsigned long address, struct page *page, u64 gva),
+	TP_ARGS(address, page, gva),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, address)
+		__field(pfn_t, pfn)
+		__field(u64, gva)
+		),
+
+	TP_fast_assign(
+		__entry->address = address;
+		__entry->pfn = page ? page_to_pfn(page) : 0;
+		__entry->gva = gva;
+		),
+
+	TP_printk("gva %#llx address %#lx pfn %#llx",  __entry->gva,
+		  __entry->address, __entry->pfn)
+);
+
+TRACE_EVENT(
+	kvm_async_pf_doublefault,
+	TP_PROTO(u64 gva, u64 gfn),
+	TP_ARGS(gva, gfn),
+
+	TP_STRUCT__entry(
+		__field(u64, gva)
+		__field(u64, gfn)
+		),
+
+	TP_fast_assign(
+		__entry->gva = gva;
+		__entry->gfn = gfn;
+		),
+
+	TP_printk("gva = %#llx, gfn = %#llx", __entry->gva, __entry->gfn)
+);
+
+#endif
+
 #endif /* _TRACE_KVM_MAIN_H */
 
 /* This part must be outside protection */
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 7f1178f..f63ccb0 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -15,3 +15,6 @@ config KVM_APIC_ARCHITECTURE
 
 config KVM_MMIO
        bool
+
+config KVM_ASYNC_PF
+       bool
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
new file mode 100644
index 0000000..8b144d5
--- /dev/null
+++ b/virt/kvm/async_pf.c
@@ -0,0 +1,190 @@
+/*
+ * kvm asynchronous fault support
+ *
+ * Copyright 2010 Red Hat, Inc.
+ *
+ * Author:
+ *      Gleb Natapov <gleb@redhat.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mmu_context.h>
+
+#include "async_pf.h"
+#include <trace/events/kvm.h>
+
+static struct kmem_cache *async_pf_cache;
+
+int kvm_async_pf_init(void)
+{
+	async_pf_cache = KMEM_CACHE(kvm_async_pf, 0);
+
+	if (!async_pf_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void kvm_async_pf_deinit(void)
+{
+	if (async_pf_cache)
+		kmem_cache_destroy(async_pf_cache);
+	async_pf_cache = NULL;
+}
+
+void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
+{
+	INIT_LIST_HEAD(&vcpu->async_pf.done);
+	INIT_LIST_HEAD(&vcpu->async_pf.queue);
+	spin_lock_init(&vcpu->async_pf.lock);
+}
+
+static void async_pf_execute(struct work_struct *work)
+{
+	struct page *page = NULL;
+	struct kvm_async_pf *apf =
+		container_of(work, struct kvm_async_pf, work);
+	struct mm_struct *mm = apf->mm;
+	struct kvm_vcpu *vcpu = apf->vcpu;
+	unsigned long addr = apf->addr;
+	gva_t gva = apf->gva;
+
+	might_sleep();
+
+	use_mm(mm);
+	down_read(&mm->mmap_sem);
+	get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
+	up_read(&mm->mmap_sem);
+	unuse_mm(mm);
+
+	spin_lock(&vcpu->async_pf.lock);
+	list_add_tail(&apf->link, &vcpu->async_pf.done);
+	apf->page = page;
+	apf->done = true;
+	spin_unlock(&vcpu->async_pf.lock);
+
+	/*
+	 * apf may be freed by kvm_check_async_pf_completion() after
+	 * this point
+	 */
+
+	trace_kvm_async_pf_completed(addr, page, gva);
+
+	if (waitqueue_active(&vcpu->wq))
+		wake_up_interruptible(&vcpu->wq);
+
+	mmdrop(mm);
+	kvm_put_kvm(vcpu->kvm);
+}
+
+void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
+{
+	/* cancel outstanding work queue item */
+	while (!list_empty(&vcpu->async_pf.queue)) {
+		struct kvm_async_pf *work =
+			list_entry(vcpu->async_pf.queue.next,
+				   typeof(*work), queue);
+		cancel_work_sync(&work->work);
+		list_del(&work->queue);
+		if (!work->done) /* work was canceled */
+			kmem_cache_free(async_pf_cache, work);
+	}
+
+	spin_lock(&vcpu->async_pf.lock);
+	while (!list_empty(&vcpu->async_pf.done)) {
+		struct kvm_async_pf *work =
+			list_entry(vcpu->async_pf.done.next,
+				   typeof(*work), link);
+		list_del(&work->link);
+		if (work->page)
+			put_page(work->page);
+		kmem_cache_free(async_pf_cache, work);
+	}
+	spin_unlock(&vcpu->async_pf.lock);
+
+	vcpu->async_pf.queued = 0;
+}
+
+void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
+{
+	struct kvm_async_pf *work;
+
+	if (list_empty_careful(&vcpu->async_pf.done))
+		return;
+
+	spin_lock(&vcpu->async_pf.lock);
+	work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
+	list_del(&work->link);
+	spin_unlock(&vcpu->async_pf.lock);
+
+	kvm_arch_async_page_present(vcpu, work);
+
+	list_del(&work->queue);
+	vcpu->async_pf.queued--;
+	if (work->page)
+		put_page(work->page);
+	kmem_cache_free(async_pf_cache, work);
+}
+
+int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
+		       struct kvm_arch_async_pf *arch)
+{
+	struct kvm_async_pf *work;
+
+	if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
+		return 0;
+
+	/* setup delayed work */
+
+	/*
+	 * do alloc nowait since if we are going to sleep anyway we
+	 * may as well sleep faulting in page
+	 */
+	work = kmem_cache_zalloc(async_pf_cache, GFP_NOWAIT);
+	if (!work)
+		return 0;
+
+	work->page = NULL;
+	work->done = false;
+	work->vcpu = vcpu;
+	work->gva = gva;
+	work->addr = gfn_to_hva(vcpu->kvm, gfn);
+	work->arch = *arch;
+	work->mm = current->mm;
+	atomic_inc(&work->mm->mm_count);
+	kvm_get_kvm(work->vcpu->kvm);
+
+	/* this can't really happen otherwise gfn_to_pfn_async
+	   would succeed */
+	if (unlikely(kvm_is_error_hva(work->addr)))
+		goto retry_sync;
+
+	INIT_WORK(&work->work, async_pf_execute);
+	if (!schedule_work(&work->work))
+		goto retry_sync;
+
+	list_add_tail(&work->queue, &vcpu->async_pf.queue);
+	vcpu->async_pf.queued++;
+	kvm_arch_async_page_not_present(vcpu, work);
+	return 1;
+retry_sync:
+	kvm_put_kvm(work->vcpu->kvm);
+	mmdrop(work->mm);
+	kmem_cache_free(async_pf_cache, work);
+	return 0;
+}
diff --git a/virt/kvm/async_pf.h b/virt/kvm/async_pf.h
new file mode 100644
index 0000000..fa15074
--- /dev/null
+++ b/virt/kvm/async_pf.h
@@ -0,0 +1,36 @@
+/*
+ * kvm asynchronous fault support
+ *
+ * Copyright 2010 Red Hat, Inc.
+ *
+ * Author:
+ *      Gleb Natapov <gleb@redhat.com>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __KVM_ASYNC_PF_H__
+#define __KVM_ASYNC_PF_H__
+
+#ifdef CONFIG_KVM_ASYNC_PF
+int kvm_async_pf_init(void);
+void kvm_async_pf_deinit(void);
+void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu);
+#else
+#define kvm_async_pf_init() (0)
+#define kvm_async_pf_deinit() do{}while(0)
+#define kvm_async_pf_vcpu_init(C) do{}while(0)
+#endif
+
+#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1aeeb7f..238079e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -55,6 +55,7 @@
 #include <asm-generic/bitops/le.h>
 
 #include "coalesced_mmio.h"
+#include "async_pf.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/kvm.h>
@@ -186,6 +187,7 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id)
 	vcpu->kvm = kvm;
 	vcpu->vcpu_id = id;
 	init_waitqueue_head(&vcpu->wq);
+	kvm_async_pf_vcpu_init(vcpu);
 
 	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (!page) {
@@ -948,17 +950,29 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
-static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
+static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
+			bool *async)
 {
 	struct page *page[1];
-	int npages;
+	int npages = 0;
 	pfn_t pfn;
 
-	if (atomic)
+	/* we can do it either atomically or asynchronously, not both */
+	BUG_ON(atomic && async);
+
+	if (atomic || async)
 		npages = __get_user_pages_fast(addr, 1, 1, page);
-	else {
+
+	if (unlikely(npages != 1) && !atomic) {
 		might_sleep();
-		npages = get_user_pages_fast(addr, 1, 1, page);
+
+		if (async) {
+			down_read(&current->mm->mmap_sem);
+			npages = get_user_pages_noio(current, current->mm,
+						     addr, 1, 1, 0, page, NULL);
+			up_read(&current->mm->mmap_sem);
+		} else
+			npages = get_user_pages_fast(addr, 1, 1, page);
 	}
 
 	if (unlikely(npages != 1)) {
@@ -978,6 +992,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
+			if (async && !(vma->vm_flags & VM_PFNMAP) &&
+			    (vma->vm_flags & VM_WRITE))
+				*async = true;
 			up_read(&current->mm->mmap_sem);
 return_fault_page:
 			get_page(fault_page);
@@ -995,32 +1012,41 @@ return_fault_page:
 
 pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr)
 {
-	return hva_to_pfn(kvm, addr, true);
+	return hva_to_pfn(kvm, addr, true, NULL);
 }
 EXPORT_SYMBOL_GPL(hva_to_pfn_atomic);
 
-static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic)
+static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async)
 {
 	unsigned long addr;
 
+	if (async)
+		*async = false;
+
 	addr = gfn_to_hva(kvm, gfn);
 	if (kvm_is_error_hva(addr)) {
 		get_page(bad_page);
 		return page_to_pfn(bad_page);
 	}
 
-	return hva_to_pfn(kvm, addr, atomic);
+	return hva_to_pfn(kvm, addr, atomic, async);
 }
 
 pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
 {
-	return __gfn_to_pfn(kvm, gfn, true);
+	return __gfn_to_pfn(kvm, gfn, true, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_atomic);
 
+pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async)
+{
+	return __gfn_to_pfn(kvm, gfn, false, async);
+}
+EXPORT_SYMBOL_GPL(gfn_to_pfn_async);
+
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
 {
-	return __gfn_to_pfn(kvm, gfn, false);
+	return __gfn_to_pfn(kvm, gfn, false, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn);
 
@@ -1028,7 +1054,7 @@ pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
 			 struct kvm_memory_slot *slot, gfn_t gfn)
 {
 	unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-	return hva_to_pfn(kvm, addr, false);
+	return hva_to_pfn(kvm, addr, false, NULL);
 }
 
 int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages,
@@ -2335,6 +2361,10 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 		goto out_free_5;
 	}
 
+	r = kvm_async_pf_init();
+	if (r)
+		goto out_free;
+
 	kvm_chardev_ops.owner = module;
 	kvm_vm_fops.owner = module;
 	kvm_vcpu_fops.owner = module;
@@ -2342,7 +2372,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 	r = misc_register(&kvm_dev);
 	if (r) {
 		printk(KERN_ERR "kvm: misc device register failed\n");
-		goto out_free;
+		goto out_unreg;
 	}
 
 	kvm_preempt_ops.sched_in = kvm_sched_in;
@@ -2352,6 +2382,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 
 	return 0;
 
+out_unreg:
+	kvm_async_pf_deinit();
 out_free:
 	kmem_cache_destroy(kvm_vcpu_cache);
 out_free_5:
@@ -2384,6 +2416,7 @@ void kvm_exit(void)
 	kvm_exit_debug();
 	misc_deregister(&kvm_dev);
 	kmem_cache_destroy(kvm_vcpu_cache);
+	kvm_async_pf_deinit();
 	sysdev_unregister(&kvm_sysdev);
 	sysdev_class_unregister(&kvm_sysdev_class);
 	unregister_reboot_notifier(&kvm_reboot_notifier);
