4 files changed, 88 insertions, 1 deletions

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index 3e8684e48506..36594ba57723 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -617,6 +617,42 @@ struct kvm_xen_hvm_config {
         __u8 pad2[30];
 };
 
+4.27 KVM_GET_CLOCK
+
+Capability: KVM_CAP_ADJUST_CLOCK
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_clock_data (out)
+Returns: 0 on success, -1 on error
+
+Gets the current timestamp of kvmclock as seen by the current guest. In
+conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
+such as migration.
+
+struct kvm_clock_data {
+        __u64 clock;  /* kvmclock current value */
+        __u32 flags;
+        __u32 pad[9];
+};
+
+4.28 KVM_SET_CLOCK
+
+Capability: KVM_CAP_ADJUST_CLOCK
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_clock_data (in)
+Returns: 0 on success, -1 on error
+
+Sets the current timestamp of kvmclock to the valued specific in its parameter.
+In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
+such as migration.
+
+struct kvm_clock_data {
+        __u64 clock;  /* kvmclock current value */
+        __u32 flags;
+        __u32 pad[9];
+};
+
 5. The kvm_run structure
 
 Application code obtains a pointer to the kvm_run structure by
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4d994ad5051a..0558ff8c32ae 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -413,6 +413,7 @@ struct kvm_arch{
 
         unsigned long irq_sources_bitmap;
         u64 vm_init_tsc;
+        s64 kvmclock_offset;
 
         struct kvm_xen_hvm_config xen_hvm_config;
 };
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 13f30aac460b..e16cdc9ec0c1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -680,7 +680,8 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
         /* With all the info we got, fill in the values */
 
         vcpu->hv_clock.system_time = ts.tv_nsec +
-                                     (NSEC_PER_SEC * (u64)ts.tv_sec);
+                                     (NSEC_PER_SEC * (u64)ts.tv_sec) + v->kvm->arch.kvmclock_offset;
+
         /*
          * The interface expects us to write an even number signaling that the
          * update is finished. Since the guest won't see the intermediate
@@ -1262,6 +1263,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_PIT_STATE2:
         case KVM_CAP_SET_IDENTITY_MAP_ADDR:
         case KVM_CAP_XEN_HVM:
+        case KVM_CAP_ADJUST_CLOCK:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO:
@@ -2468,6 +2470,44 @@ long kvm_arch_vm_ioctl(struct file *filp,
                 r = 0;
                 break;
         }
+        case KVM_SET_CLOCK: {
+                struct timespec now;
+                struct kvm_clock_data user_ns;
+                u64 now_ns;
+                s64 delta;
+
+                r = -EFAULT;
+                if (copy_from_user(&user_ns, argp, sizeof(user_ns)))
+                        goto out;
+
+                r = -EINVAL;
+                if (user_ns.flags)
+                        goto out;
+
+                r = 0;
+                ktime_get_ts(&now);
+                now_ns = timespec_to_ns(&now);
+                delta = user_ns.clock - now_ns;
+                kvm->arch.kvmclock_offset = delta;
+                break;
+        }
+        case KVM_GET_CLOCK: {
+                struct timespec now;
+                struct kvm_clock_data user_ns;
+                u64 now_ns;
+
+                ktime_get_ts(&now);
+                now_ns = timespec_to_ns(&now);
+                user_ns.clock = kvm->arch.kvmclock_offset + now_ns;
+                user_ns.flags = 0;
+
+                r = -EFAULT;
+                if (copy_to_user(argp, &user_ns, sizeof(user_ns)))
+                        goto out;
+                r = 0;
+                break;
+        }
+
         default:
                 ;
         }
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index b694c1d2f918..6ed1a12ed526 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -439,6 +439,7 @@ struct kvm_ioeventfd {
 #ifdef __KVM_HAVE_XEN_HVM
 #define KVM_CAP_XEN_HVM 38
 #endif
+#define KVM_CAP_ADJUST_CLOCK 39
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -512,6 +513,12 @@ struct kvm_irqfd {
         __u8  pad[20];
 };
 
+struct kvm_clock_data {
+        __u64 clock;
+        __u32 flags;
+        __u32 pad[9];
+};
+
 /*
  * ioctls for VM fds
  */
@@ -562,6 +569,9 @@ struct kvm_irqfd {
 #define KVM_SET_BOOT_CPU_ID        _IO(KVMIO, 0x78)
 #define KVM_IOEVENTFD             _IOW(KVMIO, 0x79, struct kvm_ioeventfd)
 #define KVM_XEN_HVM_CONFIG        _IOW(KVMIO, 0x7a, struct kvm_xen_hvm_config)
+#define KVM_SET_CLOCK             _IOW(KVMIO, 0x7b, struct kvm_clock_data)
+#define KVM_GET_CLOCK             _IOR(KVMIO, 0x7c, struct kvm_clock_data)
+
 
 /*
  * ioctls for vcpu fds