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hv_utils: drain the timesync packets on onchannelcallback

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commit b46b4a8a57c377b72a98c7930a9f6969d2d4784e upstream.

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>
[ The upstream commit uses HV_HYP_PAGE_SIZE, which is not defined in 4.19.y.
  Fixed this manually for 4.19.y by using PAGE_SIZE instead.

  If there are multiple messages in the host-to-guest ringbuffer of the TimeSync
  device, 4.19.y only handles 1 message, and later the host puts new messages
  into the ringbuffer without signaling the guest because the ringbuffer is not
  empty, causing a "hung" ringbuffer. Backported the mainline fix for this issue. ]
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 1af0a35eba1ee302fc30aea8cb621f6de8728785)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
This commit is contained in:
Vineeth Pillai 2020-08-21 15:28:49 +00:00 committed by Vegard Nossum
parent 948b6135a2
commit 22749c2b34
1 changed files with 16 additions and 3 deletions
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19
drivers/hv/hv_util.c
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@ -294,10 +294,23 @@ 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,
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,
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)];