linux-kernel - [PATCH V2 1/1] hv: do not lose pending heartbeat vmbus packets

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Date:   Wed,  5 Oct 2016 16:57:46 -0700
From:   kys@...hange.microsoft.com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        leann.ogasawara@...onical.com
Cc:     Long Li <longli@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stable <stable@...r.kernel.org>
Subject: [PATCH V2 1/1] hv: do not lose pending heartbeat vmbus packets

From: Long Li <longli@...rosoft.com>

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 the
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 <longli@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
CC: Stable <stable@...r.kernel.org>
---
	V2: Submit the patch to stable as well - Joshua R. Poulson <jrp@....org>
 
 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)];
 
-- 
1.7.4.1