Public bug reported:

Hyper-V hosts can continue sending heartbeat packets to guests
independent of whether earlier packets have responses, which led to a
potential issue of these packets being dropped when responses took too
long to process. Lost heartbeats will lead to the host diagnosing that
the guest is dead and should be shut down and restarted.

The following patch was submitted upstream but has not yet been
accepted. I will add the upstream commit ID once the patch goes into

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 <>
CC: Stable <>
        V2: Submit the patch to stable as well - Joshua R. Poulson 

 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)];

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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

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