[PATCH v2 0/2] hv_utils: TimeSync fixes

[PATCH v2 0/2] hv_utils: TimeSync fixes

[Vitaly Kuznetsov]

This series is a succesor of the previously sent "hv_utils: drop
.getcrosststamp() support from PTP driver" patch. A new unrelated issue
with TimeSync on pre-TimeSync-v4 hosts was discovered but as these patches
are tangled I'm sending them out in a single series.

Vitaly Kuznetsov (2):
  hv_utils: drop .getcrosststamp() support from PTP driver
  hv_utils: fix TimeSync work on pre-TimeSync-v4 hosts

 drivers/hv/hv_util.c | 164 +++++++++++++++++----------------------------------
 1 file changed, 54 insertions(+), 110 deletions(-)

-- 
2.9.3

[PATCH v2 1/2] hv_utils: drop .getcrosststamp() support from PTP driver

[Vitaly Kuznetsov]

Turns out that our implementation of .getcrosststamp() never actually
worked. Hyper-V is sending time samples every 5 seconds and this is
too much for get_device_system_crosststamp() as it's interpolation
algorithm (which nobody is currently using in kernel, btw) accounts
for a 'slow' device but we're not slow in Hyper-V, our time reference
is too far away.

.getcrosststamp() is not currently used, get_device_system_crosststamp()
almost always returns -EINVAL and client falls back to using PTP_SYS_OFFSET
so this patch doesn't change much. I also tried doing interpolation
manually (e.g. the same way hv_ptp_gettime() works and it turns out that
we're getting even lower quality:

PTP_SYS_OFFSET_PRECISE with manual interpolation:
* PHC0                     0   3    37     4  -3974ns[-5338ns] +/-  977ns
* PHC0                     0   3    77     7  +2227ns[+3184ns] +/-  576ns
* PHC0                     0   3   177    10  +3060ns[+5220ns] +/-  548ns
* PHC0                     0   3   377    12  +3937ns[+4371ns] +/- 1414ns
* PHC0                     0   3   377     6   +764ns[+1240ns] +/- 1047ns
* PHC0                     0   3   377     7  -1210ns[-3731ns] +/-  479ns
* PHC0                     0   3   377     9   +153ns[-1019ns] +/-  406ns
* PHC0                     0   3   377    12   -872ns[-1793ns] +/-  443ns
* PHC0                     0   3   377     5   +701ns[+3599ns] +/-  426ns
* PHC0                     0   3   377     5   -923ns[ -375ns] +/- 1062ns

PTP_SYS_OFFSET:
* PHC0                     0   3     7     5    +72ns[+8020ns] +/-  251ns
* PHC0                     0   3    17     5   -885ns[-3661ns] +/-  254ns
* PHC0                     0   3    37     6   -454ns[-5732ns] +/-  258ns
* PHC0                     0   3    77    10  +1183ns[+3754ns] +/-  164ns
* PHC0                     0   3   377     5   +579ns[+1137ns] +/-  110ns
* PHC0                     0   3   377     7   +501ns[+1064ns] +/-   96ns
* PHC0                     0   3   377     9  +1641ns[+3342ns] +/-  106ns
* PHC0                     0   3   377     8    -47ns[  +77ns] +/-  160ns
* PHC0                     0   3   377     5    +54ns[ +107ns] +/-  102ns
* PHC0                     0   3   377     8   -354ns[ -617ns] +/-   89ns

This fact wasn't noticed during the initial testing of the PTP device
somehow but got revealed now. Let's just drop .getcrosststamp()
implementation for now as it doesn't seem to be suitable for us.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hv_util.c | 36 ------------------------------------
 1 file changed, 36 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 186b100..2849143 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -248,7 +248,6 @@ static struct adj_time_work  wrk;
 static struct {
 	u64				host_time;
 	u64				ref_time;
-	struct system_time_snapshot	snap;
 	spinlock_t			lock;
 } host_ts;
 
@@ -281,7 +280,6 @@ static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags)
 		cur_reftime = hyperv_cs->read(hyperv_cs);
 		host_ts.host_time = hosttime;
 		host_ts.ref_time = cur_reftime;
-		ktime_get_snapshot(&host_ts.snap);
 
 		/*
 		 * TimeSync v4 messages contain reference time (guest's Hyper-V
@@ -538,46 +536,12 @@ static int hv_ptp_gettime(struct ptp_clock_info *info, struct timespec64 *ts)
 	return 0;
 }
 
-static int hv_ptp_get_syncdevicetime(ktime_t *device,
-				     struct system_counterval_t *system,
-				     void *ctx)
-{
-	system->cs = hyperv_cs;
-	system->cycles = host_ts.ref_time;
-	*device = ns_to_ktime((host_ts.host_time - WLTIMEDELTA) * 100);
-
-	return 0;
-}
-
-static int hv_ptp_getcrosststamp(struct ptp_clock_info *ptp,
-				 struct system_device_crosststamp *xtstamp)
-{
-	unsigned long flags;
-	int ret;
-
-	spin_lock_irqsave(&host_ts.lock, flags);
-
-	/*
-	 * host_ts contains the last time sample from the host and the snapshot
-	 * of system time. We don't need to calculate the time delta between
-	 * the reception and now as get_device_system_crosststamp() does the
-	 * required interpolation.
-	 */
-	ret = get_device_system_crosststamp(hv_ptp_get_syncdevicetime,
-					    NULL, &host_ts.snap, xtstamp);
-
-	spin_unlock_irqrestore(&host_ts.lock, flags);
-
-	return ret;
-}
-
 static struct ptp_clock_info ptp_hyperv_info = {
 	.name		= "hyperv",
 	.enable         = hv_ptp_enable,
 	.adjtime        = hv_ptp_adjtime,
 	.adjfreq        = hv_ptp_adjfreq,
 	.gettime64      = hv_ptp_gettime,
-	.getcrosststamp = hv_ptp_getcrosststamp,
 	.settime64      = hv_ptp_settime,
 	.owner		= THIS_MODULE,
 };
-- 
2.9.3

[PATCH v2 2/2] hv_utils: fix TimeSync job on pre-TimeSync-v4 hosts

[Vitaly Kuznetsov]

It was found that ICTIMESYNCFLAG_SYNC packets are handled incorrectly
on WS2012R2, e.g. after the guest is paused and resumed its time is set
to something different from host's time. The problem is that we call
adj_guesttime() with reftime=0 for these old hosts and we don't account
for that in 'if (adj_flags & ICTIMESYNCFLAG_SYNC)' branch and
hv_set_host_time().

While we could've solved this by adding a check like
 'if (ts_srv_version > TS_VERSION_3)' to hv_set_host_time() I prefer
to do some refactoring. We don't need to have two separate containers
for host samples, struct host_ts which we use for PTP is enough.

Throw away 'struct adj_time_work' and create hv_get_adj_host_time()
accessor to host_ts to avoid code duplication.

Fixes: 3716a49a81ba ("hv_utils: implement Hyper-V PTP source")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hv_util.c | 128 ++++++++++++++++++++++-----------------------------
 1 file changed, 54 insertions(+), 74 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 2849143..14dce25 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -202,27 +202,39 @@ static void shutdown_onchannelcallback(void *context)
 /*
  * Set the host time in a process context.
  */
+static struct work_struct adj_time_work;
 
-struct adj_time_work {
-	struct work_struct work;
-	u64	host_time;
-	u64	ref_time;
-	u8	flags;
-};
+/*
+ * The last time sample, received from the host. PTP device responds to
+ * requests by using this data and the current partition-wide time reference
+ * count.
+ */
+static struct {
+	u64				host_time;
+	u64				ref_time;
+	spinlock_t			lock;
+} host_ts;
 
-static void hv_set_host_time(struct work_struct *work)
+static struct timespec64 hv_get_adj_host_time(void)
 {
-	struct adj_time_work *wrk;
-	struct timespec64 host_ts;
-	u64 reftime, newtime;
-
-	wrk = container_of(work, struct adj_time_work, work);
+	struct timespec64 ts;
+	u64 newtime, reftime;
+	unsigned long flags;
 
+	spin_lock_irqsave(&host_ts.lock, flags);
 	reftime = hyperv_cs->read(hyperv_cs);
-	newtime = wrk->host_time + (reftime - wrk->ref_time);
-	host_ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
+	newtime = host_ts.host_time + (reftime - host_ts.ref_time);
+	ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
+	spin_unlock_irqrestore(&host_ts.lock, flags);
 
-	do_settimeofday64(&host_ts);
+	return ts;
+}
+
+static void hv_set_host_time(struct work_struct *work)
+{
+	struct timespec64 ts = hv_get_adj_host_time();
+
+	do_settimeofday64(&ts);
 }
 
 /*
@@ -238,60 +250,35 @@ 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 struct adj_time_work  wrk;
-
-/*
- * The last time sample, received from the host. PTP device responds to
- * requests by using this data and the current partition-wide time reference
- * count.
- */
-static struct {
-	u64				host_time;
-	u64				ref_time;
-	spinlock_t			lock;
-} host_ts;
-
 static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags)
 {
 	unsigned long flags;
 	u64 cur_reftime;
 
 	/*
-	 * This check is safe since we are executing in the
-	 * interrupt context and time synch messages are always
-	 * delivered on the same CPU.
+	 * Save the adjusted time sample from the host and the snapshot
+	 * of the current system time.
 	 */
-	if (adj_flags & ICTIMESYNCFLAG_SYNC) {
-		/* Queue a job to do do_settimeofday64() */
-		if (work_pending(&wrk.work))
-			return;
-
-		wrk.host_time = hosttime;
-		wrk.ref_time = reftime;
-		wrk.flags = adj_flags;
-		schedule_work(&wrk.work);
-	} else {
-		/*
-		 * Save the adjusted time sample from the host and the snapshot
-		 * of the current system time for PTP device.
-		 */
-		spin_lock_irqsave(&host_ts.lock, flags);
-
-		cur_reftime = hyperv_cs->read(hyperv_cs);
-		host_ts.host_time = hosttime;
-		host_ts.ref_time = cur_reftime;
-
-		/*
-		 * TimeSync v4 messages contain reference time (guest's Hyper-V
-		 * clocksource read when the time sample was generated), we can
-		 * improve the precision by adding the delta between now and the
-		 * time of generation.
-		 */
-		if (ts_srv_version > TS_VERSION_3)
-			host_ts.host_time += (cur_reftime - reftime);
-
-		spin_unlock_irqrestore(&host_ts.lock, flags);
-	}
+	spin_lock_irqsave(&host_ts.lock, flags);
+
+	cur_reftime = hyperv_cs->read(hyperv_cs);
+	host_ts.host_time = hosttime;
+	host_ts.ref_time = cur_reftime;
+
+	/*
+	 * TimeSync v4 messages contain reference time (guest's Hyper-V
+	 * clocksource read when the time sample was generated), we can
+	 * improve the precision by adding the delta between now and the
+	 * time of generation. For older protocols we set
+	 * reftime == cur_reftime on call.
+	 */
+	host_ts.host_time += (cur_reftime - reftime);
+
+	spin_unlock_irqrestore(&host_ts.lock, flags);
+
+	/* Schedule work to do do_settimeofday64() */
+	if (adj_flags & ICTIMESYNCFLAG_SYNC)
+		schedule_work(&adj_time_work);
 }
 
 /*
@@ -339,8 +326,8 @@ static void timesync_onchannelcallback(void *context)
 					sizeof(struct vmbuspipe_hdr) +
 					sizeof(struct icmsg_hdr)];
 				adj_guesttime(timedatap->parenttime,
-						0,
-						timedatap->flags);
+					      hyperv_cs->read(hyperv_cs),
+					      timedatap->flags);
 			}
 		}
 
@@ -524,14 +511,7 @@ static int hv_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 
 static int hv_ptp_gettime(struct ptp_clock_info *info, struct timespec64 *ts)
 {
-	unsigned long flags;
-	u64 newtime, reftime;
-
-	spin_lock_irqsave(&host_ts.lock, flags);
-	reftime = hyperv_cs->read(hyperv_cs);
-	newtime = host_ts.host_time + (reftime - host_ts.ref_time);
-	*ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
-	spin_unlock_irqrestore(&host_ts.lock, flags);
+	*ts = hv_get_adj_host_time();
 
 	return 0;
 }
@@ -556,7 +536,7 @@ static int hv_timesync_init(struct hv_util_service *srv)
 
 	spin_lock_init(&host_ts.lock);
 
-	INIT_WORK(&wrk.work, hv_set_host_time);
+	INIT_WORK(&adj_time_work, hv_set_host_time);
 
 	/*
 	 * ptp_clock_register() returns NULL when CONFIG_PTP_1588_CLOCK is
@@ -577,7 +557,7 @@ static void hv_timesync_deinit(void)
 {
 	if (hv_ptp_clock)
 		ptp_clock_unregister(hv_ptp_clock);
-	cancel_work_sync(&wrk.work);
+	cancel_work_sync(&adj_time_work);
 }
 
 static int __init init_hyperv_utils(void)
-- 
2.9.3

[PATCH v2 2/2] hv_utils: fix TimeSync work on pre-TimeSync-v4 hosts

[Vitaly Kuznetsov]

It was found that ICTIMESYNCFLAG_SYNC packets are handled incorrectly
on WS2012R2, e.g. after the guest is paused and resumed its time is set
to something different from host's time. The problem is that we call
adj_guesttime() with reftime=0 for these old hosts and we don't account
for that in 'if (adj_flags & ICTIMESYNCFLAG_SYNC)' branch and
hv_set_host_time().

While we could've solved this by adding a check like
'if (ts_srv_version > TS_VERSION_3)' to hv_set_host_time() I prefer
to do some refactoring. We don't need to have two separate containers
for host samples, struct host_ts which we use for PTP is enough.

Throw away 'struct adj_time_work' and create hv_get_adj_host_time()
accessor to host_ts to avoid code duplication.

Fixes: 3716a49a81ba ("hv_utils: implement Hyper-V PTP source")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hv_util.c | 128 ++++++++++++++++++++++-----------------------------
 1 file changed, 54 insertions(+), 74 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 2849143..14dce25 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -202,27 +202,39 @@ static void shutdown_onchannelcallback(void *context)
 /*
  * Set the host time in a process context.
  */
+static struct work_struct adj_time_work;
 
-struct adj_time_work {
-	struct work_struct work;
-	u64	host_time;
-	u64	ref_time;
-	u8	flags;
-};
+/*
+ * The last time sample, received from the host. PTP device responds to
+ * requests by using this data and the current partition-wide time reference
+ * count.
+ */
+static struct {
+	u64				host_time;
+	u64				ref_time;
+	spinlock_t			lock;
+} host_ts;
 
-static void hv_set_host_time(struct work_struct *work)
+static struct timespec64 hv_get_adj_host_time(void)
 {
-	struct adj_time_work *wrk;
-	struct timespec64 host_ts;
-	u64 reftime, newtime;
-
-	wrk = container_of(work, struct adj_time_work, work);
+	struct timespec64 ts;
+	u64 newtime, reftime;
+	unsigned long flags;
 
+	spin_lock_irqsave(&host_ts.lock, flags);
 	reftime = hyperv_cs->read(hyperv_cs);
-	newtime = wrk->host_time + (reftime - wrk->ref_time);
-	host_ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
+	newtime = host_ts.host_time + (reftime - host_ts.ref_time);
+	ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
+	spin_unlock_irqrestore(&host_ts.lock, flags);
 
-	do_settimeofday64(&host_ts);
+	return ts;
+}
+
+static void hv_set_host_time(struct work_struct *work)
+{
+	struct timespec64 ts = hv_get_adj_host_time();
+
+	do_settimeofday64(&ts);
 }
 
 /*
@@ -238,60 +250,35 @@ 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 struct adj_time_work  wrk;
-
-/*
- * The last time sample, received from the host. PTP device responds to
- * requests by using this data and the current partition-wide time reference
- * count.
- */
-static struct {
-	u64				host_time;
-	u64				ref_time;
-	spinlock_t			lock;
-} host_ts;
-
 static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags)
 {
 	unsigned long flags;
 	u64 cur_reftime;
 
 	/*
-	 * This check is safe since we are executing in the
-	 * interrupt context and time synch messages are always
-	 * delivered on the same CPU.
+	 * Save the adjusted time sample from the host and the snapshot
+	 * of the current system time.
 	 */
-	if (adj_flags & ICTIMESYNCFLAG_SYNC) {
-		/* Queue a job to do do_settimeofday64() */
-		if (work_pending(&wrk.work))
-			return;
-
-		wrk.host_time = hosttime;
-		wrk.ref_time = reftime;
-		wrk.flags = adj_flags;
-		schedule_work(&wrk.work);
-	} else {
-		/*
-		 * Save the adjusted time sample from the host and the snapshot
-		 * of the current system time for PTP device.
-		 */
-		spin_lock_irqsave(&host_ts.lock, flags);
-
-		cur_reftime = hyperv_cs->read(hyperv_cs);
-		host_ts.host_time = hosttime;
-		host_ts.ref_time = cur_reftime;
-
-		/*
-		 * TimeSync v4 messages contain reference time (guest's Hyper-V
-		 * clocksource read when the time sample was generated), we can
-		 * improve the precision by adding the delta between now and the
-		 * time of generation.
-		 */
-		if (ts_srv_version > TS_VERSION_3)
-			host_ts.host_time += (cur_reftime - reftime);
-
-		spin_unlock_irqrestore(&host_ts.lock, flags);
-	}
+	spin_lock_irqsave(&host_ts.lock, flags);
+
+	cur_reftime = hyperv_cs->read(hyperv_cs);
+	host_ts.host_time = hosttime;
+	host_ts.ref_time = cur_reftime;
+
+	/*
+	 * TimeSync v4 messages contain reference time (guest's Hyper-V
+	 * clocksource read when the time sample was generated), we can
+	 * improve the precision by adding the delta between now and the
+	 * time of generation. For older protocols we set
+	 * reftime == cur_reftime on call.
+	 */
+	host_ts.host_time += (cur_reftime - reftime);
+
+	spin_unlock_irqrestore(&host_ts.lock, flags);
+
+	/* Schedule work to do do_settimeofday64() */
+	if (adj_flags & ICTIMESYNCFLAG_SYNC)
+		schedule_work(&adj_time_work);
 }
 
 /*
@@ -339,8 +326,8 @@ static void timesync_onchannelcallback(void *context)
 					sizeof(struct vmbuspipe_hdr) +
 					sizeof(struct icmsg_hdr)];
 				adj_guesttime(timedatap->parenttime,
-						0,
-						timedatap->flags);
+					      hyperv_cs->read(hyperv_cs),
+					      timedatap->flags);
 			}
 		}
 
@@ -524,14 +511,7 @@ static int hv_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
 
 static int hv_ptp_gettime(struct ptp_clock_info *info, struct timespec64 *ts)
 {
-	unsigned long flags;
-	u64 newtime, reftime;
-
-	spin_lock_irqsave(&host_ts.lock, flags);
-	reftime = hyperv_cs->read(hyperv_cs);
-	newtime = host_ts.host_time + (reftime - host_ts.ref_time);
-	*ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
-	spin_unlock_irqrestore(&host_ts.lock, flags);
+	*ts = hv_get_adj_host_time();
 
 	return 0;
 }
@@ -556,7 +536,7 @@ static int hv_timesync_init(struct hv_util_service *srv)
 
 	spin_lock_init(&host_ts.lock);
 
-	INIT_WORK(&wrk.work, hv_set_host_time);
+	INIT_WORK(&adj_time_work, hv_set_host_time);
 
 	/*
 	 * ptp_clock_register() returns NULL when CONFIG_PTP_1588_CLOCK is
@@ -577,7 +557,7 @@ static void hv_timesync_deinit(void)
 {
 	if (hv_ptp_clock)
 		ptp_clock_unregister(hv_ptp_clock);
-	cancel_work_sync(&wrk.work);
+	cancel_work_sync(&adj_time_work);
 }
 
 static int __init init_hyperv_utils(void)
-- 
2.9.3

Re: [PATCH v2 2/2] hv_utils: fix TimeSync job on pre-TimeSync-v4 hosts

[Vitaly Kuznetsov]

I'm sorry I screwed up,

this patch got sent twice in the series as I slightly changed the
subject and forgot to remove the old version :-(

Please disregard this one from series, "hv_utils: fix TimeSync work on
pre-TimeSync-v4 hosts" is the right one. Thanks.

-- 
  Vitaly