From 1af0a35eba1ee302fc30aea8cb621f6de8728785 Mon Sep 17 00:00:00 2001 From: Vineeth Pillai Date: Fri, 21 Aug 2020 15:28:49 +0000 Subject: [PATCH] hv_utils: drain the timesync packets on onchannelcallback 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 Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200821152849.99517-1-viremana@linux.microsoft.com Signed-off-by: Wei Liu [ 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 Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hv_util.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 2003314dcfbe..4a131efe54ef 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -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)];