Author: sephe
Date: Thu Oct 13 06:49:00 2016
New Revision: 307187
URL: https://svnweb.freebsd.org/changeset/base/307187

Log:
  MFC 305111
  
      hyperv/timesync: Rework time adjustment policy
  
      - By default, adjust time upon SYNC request.  It can be disabled
        through hw.hvtimesync.ignore_sync_req.  SYNC request will be
        sent by hypervisor the host is resumed, rebooted, etc.
      - By default, adjust time upon SAMPLE request, if there is 100ms
        difference between VM time and hypervisor time.  This can be
        disabled through hw.hvtimesync.sample_drift.
  
      And nuke the unnecessary task, since channel callback is running
      in a Hyper-V taskqueue nowadays.
  
      Submitted by:   YanZhe Chen <t-yachen microsoft com>
      Discussed with: Dexuan Cui <decui microsoft com>, Hongjiang Zhang 
<honzhan microsoft com>, sephe
      Sponsored by:   Microsoft
      Differential Revision:  https://reviews.freebsd.org/D7707

Modified:
  stable/10/sys/dev/hyperv/utilities/hv_timesync.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/dev/hyperv/utilities/hv_timesync.c
==============================================================================
--- stable/10/sys/dev/hyperv/utilities/hv_timesync.c    Thu Oct 13 06:47:02 
2016        (r307186)
+++ stable/10/sys/dev/hyperv/utilities/hv_timesync.c    Thu Oct 13 06:49:00 
2016        (r307187)
@@ -39,7 +39,7 @@
 #include <sys/timetc.h>
 #include <sys/syscallsubr.h>
 #include <sys/systm.h>
-#include <sys/taskqueue.h>
+#include <sys/sysctl.h>
 
 #include <dev/hyperv/include/hyperv.h>
 #include <dev/hyperv/include/vmbus.h>
@@ -52,11 +52,7 @@
 #define HV_ICTIMESYNCFLAG_SYNC      1
 #define HV_ICTIMESYNCFLAG_SAMPLE    2
 #define HV_NANO_SEC_PER_SEC         1000000000
-
-/* Time Sync data */
-typedef struct {
-       uint64_t data;
-} time_sync_data;
+#define HV_NANO_SEC_PER_MILLI_SEC   1000000
 
 static const struct vmbus_ic_desc vmbus_timesync_descs[] = {
        {
@@ -75,22 +71,43 @@ struct hv_ictimesync_data {
        uint8_t     flags;
 } __packed;
 
-typedef struct hv_timesync_sc {
-       hv_util_sc      util_sc;
-       struct task     task;
-       time_sync_data  time_msg;
-} hv_timesync_sc;
+/*
+ * Globals
+ */
+SYSCTL_NODE(_hw, OID_AUTO, hvtimesync, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
+    "Hyper-V timesync interface");
+
+/* Ignore the sync request when set to 1. */
+static int ignore_sync_req = 0;
+SYSCTL_INT(_hw_hvtimesync, OID_AUTO, ignore_sync_req, CTLFLAG_RWTUN,
+    &ignore_sync_req, 0,
+    "Ignore the sync request when set to 1.");
+
+/*
+ * Trigger sample sync when drift exceeds threshold (ms).
+ * Ignore the sample request when set to 0.
+ */
+static int sample_drift = 100;
+SYSCTL_INT(_hw_hvtimesync, OID_AUTO, sample_drift, CTLFLAG_RWTUN,
+    &sample_drift, 0,
+    "Threshold that makes sample request trigger the sync.");
 
 /**
- * Set host time based on time sync message from host
+ * @brief Synchronize time with host after reboot, restore, etc.
+ *
+ * ICTIMESYNCFLAG_SYNC flag bit indicates reboot, restore events of the VM.
+ * After reboot the flag ICTIMESYNCFLAG_SYNC is included in the first time
+ * message after the timesync channel is opened. Since the hv_utils module is
+ * loaded after hv_vmbus, the first message is usually missed. The other
+ * thing is, systime is automatically set to emulated hardware clock which may
+ * not be UTC time or in the same time zone. So, to override these effects, we
+ * use the first 50 time samples for initial system time setting.
  */
-static void
-hv_set_host_time(void *context, int pending)
+static inline
+void hv_adj_guesttime(hv_util_sc *sc, uint64_t hosttime, uint8_t flags)
 {
-       hv_timesync_sc *softc = (hv_timesync_sc*)context;
-       uint64_t hosttime = softc->time_msg.data;
        struct timespec guest_ts, host_ts;
-       uint64_t host_tns;
+       uint64_t host_tns, guest_tns;
        int64_t diff;
        int error;
 
@@ -99,37 +116,35 @@ hv_set_host_time(void *context, int pend
        host_ts.tv_nsec = (long)(host_tns%HV_NANO_SEC_PER_SEC);
 
        nanotime(&guest_ts);
+       guest_tns = guest_ts.tv_sec * HV_NANO_SEC_PER_SEC + guest_ts.tv_nsec;
 
-       diff = (int64_t)host_ts.tv_sec - (int64_t)guest_ts.tv_sec;
+       if ((flags & HV_ICTIMESYNCFLAG_SYNC) != 0 && ignore_sync_req == 0) {
+               if (bootverbose) {
+                       device_printf(sc->ic_dev, "handle sync request "
+                           "{host: %ju, guest: %ju}\n",
+                           (uintmax_t)host_tns, (uintmax_t)guest_tns);
+               }
 
-       /*
-        * If host differs by 5 seconds then make the guest catch up
-        */
-       if (diff > 5 || diff < -5) {
                error = kern_clock_settime(curthread, CLOCK_REALTIME,
                    &host_ts);
+               return;
        }
-}
 
-/**
- * @brief Synchronize time with host after reboot, restore, etc.
- *
- * ICTIMESYNCFLAG_SYNC flag bit indicates reboot, restore events of the VM.
- * After reboot the flag ICTIMESYNCFLAG_SYNC is included in the first time
- * message after the timesync channel is opened. Since the hv_utils module is
- * loaded after hv_vmbus, the first message is usually missed. The other
- * thing is, systime is automatically set to emulated hardware clock which may
- * not be UTC time or in the same time zone. So, to override these effects, we
- * use the first 50 time samples for initial system time setting.
- */
-static inline
-void hv_adj_guesttime(hv_timesync_sc *sc, uint64_t hosttime, uint8_t flags)
-{
-       sc->time_msg.data = hosttime;
-
-       if (((flags & HV_ICTIMESYNCFLAG_SYNC) != 0) ||
-               ((flags & HV_ICTIMESYNCFLAG_SAMPLE) != 0)) {
-               taskqueue_enqueue(taskqueue_thread, &sc->task);
+       if ((flags & HV_ICTIMESYNCFLAG_SAMPLE) != 0 && sample_drift != 0) {
+               if (bootverbose) {
+                       device_printf(sc->ic_dev, "handle sample request "
+                           "{host: %ju, guest: %ju}\n",
+                           (uintmax_t)host_tns, (uintmax_t)guest_tns);
+               }
+
+               diff = (int64_t)(host_tns - guest_tns) / 
HV_NANO_SEC_PER_MILLI_SEC;
+               if (diff > sample_drift || diff < -sample_drift) {
+                       error = kern_clock_settime(curthread, CLOCK_REALTIME,
+                           &host_ts);
+                       if (bootverbose)
+                               device_printf(sc->ic_dev, "trigger sample 
sync");
+               }
+               return;
        }
 }
 
@@ -145,12 +160,12 @@ hv_timesync_cb(struct vmbus_channel *cha
        int                     ret;
        uint8_t*                time_buf;
        struct hv_ictimesync_data* timedatap;
-       hv_timesync_sc          *softc;
+       hv_util_sc              *softc;
 
-       softc = (hv_timesync_sc*)context;
-       time_buf = softc->util_sc.receive_buffer;
+       softc = (hv_util_sc*)context;
+       time_buf = softc->receive_buffer;
 
-       recvlen = softc->util_sc.ic_buflen;
+       recvlen = softc->ic_buflen;
        ret = vmbus_chan_recv(channel, time_buf, &recvlen, &requestId);
        KASSERT(ret != ENOBUFS, ("hvtimesync recvbuf is not large enough"));
        /* XXX check recvlen to make sure that it contains enough data */
@@ -162,7 +177,7 @@ hv_timesync_cb(struct vmbus_channel *cha
            if (icmsghdrp->icmsgtype == HV_ICMSGTYPE_NEGOTIATE) {
                int error;
 
-               error = vmbus_ic_negomsg(&softc->util_sc, time_buf, &recvlen);
+               error = vmbus_ic_negomsg(softc, time_buf, &recvlen);
                if (error)
                        return;
            } else {
@@ -190,18 +205,12 @@ hv_timesync_probe(device_t dev)
 static int
 hv_timesync_attach(device_t dev)
 {
-       hv_timesync_sc *softc = device_get_softc(dev);
-
-       TASK_INIT(&softc->task, 1, hv_set_host_time, softc);
        return hv_util_attach(dev, hv_timesync_cb);
 }
 
 static int
 hv_timesync_detach(device_t dev)
 {
-       hv_timesync_sc *softc = device_get_softc(dev);
-
-       taskqueue_drain(taskqueue_thread, &softc->task);
        return hv_util_detach(dev);
 }
 
@@ -213,7 +222,7 @@ static device_method_t timesync_methods[
        { 0, 0 }
 };
 
-static driver_t timesync_driver = { "hvtimesync", timesync_methods, 
sizeof(hv_timesync_sc)};
+static driver_t timesync_driver = { "hvtimesync", timesync_methods, 
sizeof(hv_util_sc)};
 
 static devclass_t timesync_devclass;
 
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