4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200821152849.99517-1-viremana@xxxxxxxxxxxxxxxxxxx Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> [ 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@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/hv/hv_util.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -294,10 +294,23 @@ static void timesync_onchannelcallback(v 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)];
