[PATCHv2] Add support for async page fault to qemu

diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index 59aacd0..145c863 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -678,6 +678,9 @@  static int get_msr_entry(struct kvm_msr_entry *entry, CPUState *env)
         env->mcg_ctl = entry->data;
         break;
 #endif
+    case MSR_KVM_ASYNC_PF_EN:
+        env->async_pf_en_msr = entry->data;
+        break;
     default:
 #ifdef KVM_CAP_MCE
         if (entry->index >= MSR_MC0_CTL &&
@@ -967,6 +970,7 @@  void kvm_arch_load_regs(CPUState *env, int level)
         }
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_SYSTEM_TIME, env->system_time_msr);
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+        kvm_msr_entry_set(&msrs[n++], MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr);
     }
 #ifdef KVM_CAP_MCE
     if (env->mcg_cap) {
@@ -1186,6 +1190,7 @@  void kvm_arch_save_regs(CPUState *env)
 #endif
     msrs[n++].index = MSR_KVM_SYSTEM_TIME;
     msrs[n++].index = MSR_KVM_WALL_CLOCK;
+    msrs[n++].index = MSR_KVM_ASYNC_PF_EN;
 
 #ifdef KVM_CAP_MCE
     if (env->mcg_cap) {
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 8b6efed..6d1d6a0 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -669,6 +669,7 @@  typedef struct CPUX86State {
 #endif
     uint64_t system_time_msr;
     uint64_t wall_clock_msr;
+    uint64_t async_pf_en_msr;
 
     uint64_t tsc;
 
diff --git a/target-i386/cpuid.c b/target-i386/cpuid.c
index d63fdcb..0ee1f88 100644
--- a/target-i386/cpuid.c
+++ b/target-i386/cpuid.c
@@ -73,7 +73,7 @@  static const char *ext3_feature_name[] = {
 };
 
 static const char *kvm_feature_name[] = {
-    "kvmclock", "kvm_nopiodelay", "kvm_mmu", NULL, NULL, NULL, NULL, NULL,
+    "kvmclock", "kvm_nopiodelay", "kvm_mmu", NULL, "kvm_asyncpf", NULL, NULL, NULL,
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index f4fc063..0eb1e90 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -151,6 +151,9 @@  struct kvm_para_features {
 #ifdef KVM_CAP_PV_MMU
         { KVM_CAP_PV_MMU, KVM_FEATURE_MMU_OP },
 #endif
+#ifdef KVM_CAP_ASYNC_PF
+        { KVM_CAP_ASYNC_PF, KVM_FEATURE_ASYNC_PF },
+#endif
         { -1, -1 }
 };
 
@@ -672,6 +675,7 @@  static int kvm_put_msrs(CPUState *env, int level)
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_SYSTEM_TIME,
                           env->system_time_msr);
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+        kvm_msr_entry_set(&msrs[n++], MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr);
     }
 
     msr_data.info.nmsrs = n;
@@ -880,6 +884,7 @@  static int kvm_get_msrs(CPUState *env)
 #endif
     msrs[n++].index = MSR_KVM_SYSTEM_TIME;
     msrs[n++].index = MSR_KVM_WALL_CLOCK;
+    msrs[n++].index = MSR_KVM_ASYNC_PF_EN;
 
     msr_data.info.nmsrs = n;
     ret = kvm_vcpu_ioctl(env, KVM_GET_MSRS, &msr_data);
@@ -926,6 +931,9 @@  static int kvm_get_msrs(CPUState *env)
         case MSR_VM_HSAVE_PA:
             env->vm_hsave = msrs[i].data;
             break;
+	case MSR_KVM_ASYNC_PF_EN:
+            env->async_pf_en_msr = msrs[i].data;
+            break;
         }
     }
 
diff --git a/target-i386/machine.c b/target-i386/machine.c
index 4398801..bf14067 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -373,6 +373,24 @@  static int cpu_post_load(void *opaque, int version_id)
     return 0;
 }
 
+static bool async_pf_msr_needed(void *opaque)
+{
+    CPUState *cpu = opaque;
+
+    return cpu->async_pf_en_msr != 0;
+}
+
+static const VMStateDescription vmstate_async_pf_msr = {
+    .name = "cpu/async_pf_msr",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_UINT64(async_pf_en_msr, CPUState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_cpu = {
     .name = "cpu",
     .version_id = CPU_SAVE_VERSION,
@@ -476,6 +494,14 @@  static const VMStateDescription vmstate_cpu = {
         VMSTATE_YMMH_REGS_VARS(ymmh_regs, CPUState, CPU_NB_REGS, 12),
         VMSTATE_END_OF_LIST()
         /* The above list is not sorted /wrt version numbers, watch out! */
+    },
+    .subsections = (VMStateSubsection []) {
+        {
+            .vmsd = &vmstate_async_pf_msr,
+            .needed = async_pf_msr_needed,
+        } , {
+            /* empty */
+        }
     }
 };