hv_utils: drain the timesync packets on onchannelcallback

There could be instances where a system stall prevents the timesync
packets to be consumed. And this might lead to more than one packet
pending in the ring buffer. Current code empties one packet per callback
and it might be a stale one. So drain all the packets from ring buffer
on each callback.

Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20200821152849.99517-1-viremana@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 1f86e8d9b018d25a8dd5289a2c77d729314e70d9..a4e8d96513c22ed5b06c6944108e71f5857b9e4d 100644 (file)
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -387,10 +387,23 @@ static void timesync_onchannelcallback(void *context)
        struct ictimesync_ref_data *refdata;
        u8 *time_txf_buf = util_timesynch.recv_buffer;
 
-       vmbus_recvpacket(channel, time_txf_buf,
-                        HV_HYP_PAGE_SIZE, &recvlen, &requestid);
+       /*
+        * Drain the ring buffer and use the last packet to update
+        * host_ts
+        */
+       while (1) {
+               int ret = vmbus_recvpacket(channel, time_txf_buf,
+                                          HV_HYP_PAGE_SIZE, &recvlen,
+                                          &requestid);
+               if (ret) {
+                       pr_warn_once("TimeSync IC pkt recv failed (Err: %d)\n",
+                                    ret);
+                       break;
+               }
+
+               if (!recvlen)
+                       break;
 
-       if (recvlen > 0) {
                icmsghdrp = (struct icmsg_hdr *)&time_txf_buf[
                                sizeof(struct vmbuspipe_hdr)];