diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index dae68e68ca23..8d4a3471ad9e 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -993,20 +993,34 @@ such as migration.
 When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the
 set of bits that KVM can return in struct kvm_clock_data's flag member.
 
-The only flag defined now is KVM_CLOCK_TSC_STABLE.  If set, the returned
-value is the exact kvmclock value seen by all VCPUs at the instant
-when KVM_GET_CLOCK was called.  If clear, the returned value is simply
-CLOCK_MONOTONIC plus a constant offset; the offset can be modified
-with KVM_SET_CLOCK.  KVM will try to make all VCPUs follow this clock,
-but the exact value read by each VCPU could differ, because the host
-TSC is not stable.
+FLAGS:
+
+KVM_CLOCK_TSC_STABLE.  If set, the returned value is the exact kvmclock
+value seen by all VCPUs at the instant when KVM_GET_CLOCK was called.
+If clear, the returned value is simply CLOCK_MONOTONIC plus a constant
+offset; the offset can be modified with KVM_SET_CLOCK.  KVM will try
+to make all VCPUs follow this clock, but the exact value read by each
+VCPU could differ, because the host TSC is not stable.
+
+KVM_CLOCK_REALTIME.  If set, the `realtime` field in the kvm_clock_data
+structure is populated with the value of the host's real time
+clocksource at the instant when KVM_GET_CLOCK was called. If clear,
+the `realtime` field does not contain a value.
+
+KVM_CLOCK_HOST_TSC.  If set, the `host_tsc` field in the kvm_clock_data
+structure is populated with the value of the host's timestamp counter (TSC)
+at the instant when KVM_GET_CLOCK was called. If clear, the `host_tsc` field
+does not contain a value.
 
 ::
 
   struct kvm_clock_data {
 	__u64 clock;  /* kvmclock current value */
 	__u32 flags;
-	__u32 pad[9];
+	__u32 pad0;
+	__u64 realtime;
+	__u64 host_tsc;
+	__u32 pad[4];
   };
 
 
@@ -1023,12 +1037,22 @@ Sets the current timestamp of kvmclock to the value specified in its parameter.
 In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
 such as migration.
 
+FLAGS:
+
+KVM_CLOCK_REALTIME.  If set, KVM will compare the value of the `realtime` field
+with the value of the host's real time clocksource at the instant when
+KVM_SET_CLOCK was called. The difference in elapsed time is added to the final
+kvmclock value that will be provided to guests.
+
 ::
 
   struct kvm_clock_data {
 	__u64 clock;  /* kvmclock current value */
 	__u32 flags;
-	__u32 pad[9];
+	__u32 pad0;
+	__u64 realtime;
+	__u64 host_tsc;
+	__u32 pad[4];
   };
 
 
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6818095dd157..d6376ca8efce 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1926,4 +1926,7 @@ int kvm_cpu_dirty_log_size(void);
 
 int alloc_all_memslots_rmaps(struct kvm *kvm);
 
+#define KVM_CLOCK_VALID_FLAGS						\
+	(KVM_CLOCK_TSC_STABLE | KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC)
+
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 34287c522f4e..26f1fa263192 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2804,10 +2804,20 @@ static void get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data)
 	get_cpu();
 
 	if (__this_cpu_read(cpu_tsc_khz)) {
+#ifdef CONFIG_X86_64
+		struct timespec64 ts;
+
+		if (kvm_get_walltime_and_clockread(&ts, &data->host_tsc)) {
+			data->realtime = ts.tv_nsec + NSEC_PER_SEC * ts.tv_sec;
+			data->flags |= KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC;
+		} else
+#endif
+		data->host_tsc = rdtsc();
+
 		kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL,
 				   &hv_clock.tsc_shift,
 				   &hv_clock.tsc_to_system_mul);
-		data->clock = __pvclock_read_cycles(&hv_clock, rdtsc());
+		data->clock = __pvclock_read_cycles(&hv_clock, data->host_tsc);
 	} else {
 		data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset;
 	}
@@ -4047,7 +4057,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = KVM_SYNC_X86_VALID_FIELDS;
 		break;
 	case KVM_CAP_ADJUST_CLOCK:
-		r = KVM_CLOCK_TSC_STABLE;
+		r = KVM_CLOCK_VALID_FLAGS;
 		break;
 	case KVM_CAP_X86_DISABLE_EXITS:
 		r |=  KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE |
@@ -5834,6 +5844,60 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state)
 }
 #endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */
 
+static int kvm_vm_ioctl_get_clock(struct kvm *kvm, void __user *argp)
+{
+	struct kvm_clock_data data;
+
+	memset(&data, 0, sizeof(data));
+	get_kvmclock(kvm, &data);
+
+	if (copy_to_user(argp, &data, sizeof(data)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int kvm_vm_ioctl_set_clock(struct kvm *kvm, void __user *argp)
+{
+	struct kvm_arch *ka = &kvm->arch;
+	struct kvm_clock_data data;
+	u64 now_raw_ns;
+
+	if (copy_from_user(&data, argp, sizeof(data)))
+		return -EFAULT;
+
+	if (data.flags & ~KVM_CLOCK_REALTIME)
+		return -EINVAL;
+
+	/*
+	 * TODO: userspace has to take care of races with VCPU_RUN, so
+	 * kvm_gen_update_masterclock() can be cut down to locked
+	 * pvclock_update_vm_gtod_copy().
+	 */
+	kvm_gen_update_masterclock(kvm);
+
+	spin_lock_irq(&ka->pvclock_gtod_sync_lock);
+	if (data.flags & KVM_CLOCK_REALTIME) {
+		u64 now_real_ns = ktime_get_real_ns();
+
+		/*
+		 * Avoid stepping the kvmclock backwards.
+		 */
+		if (now_real_ns > data.realtime)
+			data.clock += now_real_ns - data.realtime;
+	}
+
+	if (ka->use_master_clock)
+		now_raw_ns = ka->master_kernel_ns;
+	else
+		now_raw_ns = get_kvmclock_base_ns();
+	ka->kvmclock_offset = data.clock - now_raw_ns;
+	spin_unlock_irq(&ka->pvclock_gtod_sync_lock);
+
+	kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE);
+	return 0;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -6077,63 +6141,12 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		break;
 	}
 #endif
-	case KVM_SET_CLOCK: {
-		struct kvm_arch *ka = &kvm->arch;
-		struct kvm_clock_data user_ns;
-		u64 now_ns;
-
-		r = -EFAULT;
-		if (copy_from_user(&user_ns, argp, sizeof(user_ns)))
-			goto out;
-
-		r = -EINVAL;
-		if (user_ns.flags)
-			goto out;
-
-		r = 0;
-		/*
-		 * TODO: userspace has to take care of races with VCPU_RUN, so
-		 * kvm_gen_update_masterclock() can be cut down to locked
-		 * pvclock_update_vm_gtod_copy().
-		 */
-		kvm_gen_update_masterclock(kvm);
-
-		/*
-		 * This pairs with kvm_guest_time_update(): when masterclock is
-		 * in use, we use master_kernel_ns + kvmclock_offset to set
-		 * unsigned 'system_time' so if we use get_kvmclock_ns() (which
-		 * is slightly ahead) here we risk going negative on unsigned
-		 * 'system_time' when 'user_ns.clock' is very small.
-		 */
-		spin_lock_irq(&ka->pvclock_gtod_sync_lock);
-		if (kvm->arch.use_master_clock)
-			now_ns = ka->master_kernel_ns;
-		else
-			now_ns = get_kvmclock_base_ns();
-		ka->kvmclock_offset = user_ns.clock - now_ns;
-		spin_unlock_irq(&ka->pvclock_gtod_sync_lock);
-
-		kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE);
+	case KVM_SET_CLOCK:
+		r = kvm_vm_ioctl_set_clock(kvm, argp);
 		break;
-	}
-	case KVM_GET_CLOCK: {
-		struct kvm_clock_data user_ns;
-
-		/*
-		 * Zero flags as it is accessed RMW, leave everything else
-		 * uninitialized as clock is always written and no other fields
-		 * are consumed.
-		 */
-		user_ns.flags = 0;
-		get_kvmclock(kvm, &user_ns);
-		memset(&user_ns.pad, 0, sizeof(user_ns.pad));
-
-		r = -EFAULT;
-		if (copy_to_user(argp, &user_ns, sizeof(user_ns)))
-			goto out;
-		r = 0;
+	case KVM_GET_CLOCK:
+		r = kvm_vm_ioctl_get_clock(kvm, argp);
 		break;
-	}
 	case KVM_MEMORY_ENCRYPT_OP: {
 		r = -ENOTTY;
 		if (kvm_x86_ops.mem_enc_op)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d9e4aabcb31a..53a49cb8616a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1223,11 +1223,16 @@ struct kvm_irqfd {
 
 /* Do not use 1, KVM_CHECK_EXTENSION returned it before we had flags.  */
 #define KVM_CLOCK_TSC_STABLE		2
+#define KVM_CLOCK_REALTIME		(1 << 2)
+#define KVM_CLOCK_HOST_TSC		(1 << 3)
 
 struct kvm_clock_data {
 	__u64 clock;
 	__u32 flags;
-	__u32 pad[9];
+	__u32 pad0;
+	__u64 realtime;
+	__u64 host_tsc;
+	__u32 pad[4];
 };
 
 /* For KVM_CAP_SW_TLB */
