[PATCH 3/3] Drivers: hv: utils: Support TimeSync version 4.0 protocol samples.

[kys@exchange.microsoft.com]

From: Alex Ng <alexng@messages.microsoft.com>

This enables support for more accurate TimeSync v4 samples when hosted
under Windows Server 2016 and newer hosts.

The new time samples include a "vmreferencetime" field that represents
the guest's TSC value when the host generated its time sample. This value
lets the guest calculate the latency in receiving the time sample. The
latency is added to the sample host time prior to updating the clock.

Signed-off-by: Alex Ng <alexng@messages.microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_util.c   |   82 ++++++++++++++++++++++++++++++++++-------------
 include/linux/hyperv.h |    9 +++++
 2 files changed, 68 insertions(+), 23 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 4002b71..6286bdc 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -37,13 +37,16 @@
 #define SD_MAJOR_1	1
 #define SD_VERSION_1	(SD_MAJOR_1 << 16 | SD_MINOR)
 
-#define TS_MAJOR	3
+#define TS_MAJOR	4
 #define TS_MINOR	0
 #define TS_VERSION	(TS_MAJOR << 16 | TS_MINOR)
 
 #define TS_MAJOR_1	1
 #define TS_VERSION_1	(TS_MAJOR_1 << 16 | TS_MINOR)
 
+#define TS_MAJOR_3	3
+#define TS_VERSION_3	(TS_MAJOR_3 << 16 | TS_MINOR)
+
 #define HB_MAJOR	3
 #define HB_MINOR	0
 #define HB_VERSION	(HB_MAJOR << 16 | HB_MINOR)
@@ -161,34 +164,43 @@ static void shutdown_onchannelcallback(void *context)
 }
 
 /*
- * Set guest time to host UTC time.
- */
-static inline void do_adj_guesttime(u64 hosttime)
-{
-	s64 host_tns;
-	struct timespec host_ts;
-
-	host_tns = (hosttime - WLTIMEDELTA) * 100;
-	host_ts = ns_to_timespec(host_tns);
-
-	do_settimeofday(&host_ts);
-}
-
-/*
  * Set the host time in a process context.
  */
 
 struct adj_time_work {
 	struct work_struct work;
 	u64	host_time;
+	u64	ref_time;
+	u8	flags;
 };
 
 static void hv_set_host_time(struct work_struct *work)
 {
 	struct adj_time_work	*wrk;
+	s64 host_tns;
+	u64 newtime;
+	struct timespec host_ts;
 
 	wrk = container_of(work, struct adj_time_work, work);
-	do_adj_guesttime(wrk->host_time);
+
+	newtime = wrk->host_time;
+	if (ts_srv_version > TS_VERSION_3) {
+		/*
+		 * Some latency has been introduced since Hyper-V generated
+		 * its time sample. Take that latency into account before
+		 * using TSC reference time sample from Hyper-V.
+		 *
+		 * This sample is given by TimeSync v4 and above hosts.
+		 */
+		u64 current_tick;
+
+		rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+		newtime += (current_tick - wrk->ref_time);
+	}
+	host_tns = (newtime - WLTIMEDELTA) * 100;
+	host_ts = ns_to_timespec(host_tns);
+
+	do_settimeofday(&host_ts);
 	kfree(wrk);
 }
 
@@ -205,7 +217,7 @@ static void hv_set_host_time(struct work_struct *work)
  * typically used as a hint to the guest. The guest is under no obligation
  * to discipline the clock.
  */
-static inline void adj_guesttime(u64 hosttime, u8 flags)
+static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 flags)
 {
 	struct adj_time_work    *wrk;
 
@@ -214,6 +226,8 @@ static inline void adj_guesttime(u64 hosttime, u8 flags)
 		return;
 
 	wrk->host_time = hosttime;
+	wrk->ref_time = reftime;
+	wrk->flags = flags;
 	if ((flags & (ICTIMESYNCFLAG_SYNC | ICTIMESYNCFLAG_SAMPLE)) != 0) {
 		INIT_WORK(&wrk->work, hv_set_host_time);
 		schedule_work(&wrk->work);
@@ -231,6 +245,7 @@ static void timesync_onchannelcallback(void *context)
 	u64 requestid;
 	struct icmsg_hdr *icmsghdrp;
 	struct ictimesync_data *timedatap;
+	struct ictimesync_ref_data *refdata;
 	u8 *time_txf_buf = util_timesynch.recv_buffer;
 	struct icmsg_negotiate *negop = NULL;
 
@@ -246,11 +261,27 @@ static void timesync_onchannelcallback(void *context)
 						time_txf_buf,
 						util_fw_version,
 						ts_srv_version);
+			pr_info("Using TimeSync version %d.%d\n",
+				ts_srv_version >> 16, ts_srv_version & 0xFFFF);
 		} else {
-			timedatap = (struct ictimesync_data *)&time_txf_buf[
-				sizeof(struct vmbuspipe_hdr) +
-				sizeof(struct icmsg_hdr)];
-			adj_guesttime(timedatap->parenttime, timedatap->flags);
+			if (ts_srv_version > TS_VERSION_3) {
+				refdata = (struct ictimesync_ref_data *)
+					&time_txf_buf[
+					sizeof(struct vmbuspipe_hdr) +
+					sizeof(struct icmsg_hdr)];
+
+				adj_guesttime(refdata->parenttime,
+						refdata->vmreferencetime,
+						refdata->flags);
+			} else {
+				timedatap = (struct ictimesync_data *)
+					&time_txf_buf[
+					sizeof(struct vmbuspipe_hdr) +
+					sizeof(struct icmsg_hdr)];
+				adj_guesttime(timedatap->parenttime,
+						0,
+						timedatap->flags);
+			}
 		}
 
 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
@@ -348,12 +379,17 @@ static int util_probe(struct hv_device *dev,
 		ts_srv_version = TS_VERSION_1;
 		hb_srv_version = HB_VERSION_1;
 		break;
-
-	default:
+	case(VERSION_WIN10):
 		util_fw_version = UTIL_FW_VERSION;
 		sd_srv_version = SD_VERSION;
 		ts_srv_version = TS_VERSION;
 		hb_srv_version = HB_VERSION;
+		break;
+	default:
+		util_fw_version = UTIL_FW_VERSION;
+		sd_srv_version = SD_VERSION;
+		ts_srv_version = TS_VERSION_3;
+		hb_srv_version = HB_VERSION;
 	}
 
 	ret = vmbus_open(dev->channel, 4 * PAGE_SIZE, 4 * PAGE_SIZE, NULL, 0,
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 430619a..7d7cbff 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1423,6 +1423,15 @@ struct ictimesync_data {
 	u8 flags;
 } __packed;
 
+struct ictimesync_ref_data {
+	u64 parenttime;
+	u64 vmreferencetime;
+	u8 flags;
+	char leapflags;
+	char stratum;
+	u8 reserved[3];
+} __packed;
+
 struct hyperv_service_callback {
 	u8 msg_type;
 	char *log_msg;
-- 
1.7.4.1