From: Long Li <>

The host keeps sending heartbeat packets independent of the
guest responding to them.  Even though we respond to the heartbeat messages at
interrupt level, we can have situations where there maybe multiple heartbeat
messages pending that have not been responded to. For instance this occurs when 
VM is paused and the host continues to send the heartbeat messages.
Address this issue by draining and responding to all
the heartbeat messages that maybe pending.

Signed-off-by: Long Li <>
Signed-off-by: K. Y. Srinivasan <>
 drivers/hv/hv_util.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 4aa3cb6..bcd0630 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -314,10 +314,14 @@ static void heartbeat_onchannelcallback(void *context)
        u8 *hbeat_txf_buf = util_heartbeat.recv_buffer;
        struct icmsg_negotiate *negop = NULL;

-       vmbus_recvpacket(channel, hbeat_txf_buf,
-                        PAGE_SIZE, &recvlen, &requestid);
+       while (1) {
+               vmbus_recvpacket(channel, hbeat_txf_buf,
+                                PAGE_SIZE, &recvlen, &requestid);
+               if (!recvlen)
+                       break;

-       if (recvlen > 0) {
                icmsghdrp = (struct icmsg_hdr *)&hbeat_txf_buf[
                                sizeof(struct vmbuspipe_hdr)];

** Changed in: linux (Ubuntu Trusty)
       Status: Triaged => Confirmed

** Changed in: linux (Ubuntu Xenial)
       Status: Triaged => Confirmed

** Changed in: linux (Ubuntu Yakkety)
       Status: Triaged => Confirmed

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  [Hyper-V] do not lose pending heartbeat vmbus packets

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