This is a note to let you know that I've just added the patch titled
Drivers: hv: balloon: account for vmbus packet header in max_pkt_size
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drivers-hv-balloon-account-for-vmbus-packet-header-i.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fbdf9350d15fbbf52d9154e7a13186598b3b7380
Author: Yanming Liu <yanminglr@xxxxxxxxx>
Date: Thu Jan 20 04:20:52 2022 +0800
Drivers: hv: balloon: account for vmbus packet header in max_pkt_size
[ Upstream commit 96d9d1fa5cd505078534113308ced0aa56d8da58 ]
Commit adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V
out of the ring buffer") introduced a notion of maximum packet size in
vmbus channel and used that size to initialize a buffer holding all
incoming packet along with their vmbus packet header. hv_balloon uses
the default maximum packet size VMBUS_DEFAULT_MAX_PKT_SIZE which matches
its maximum message size, however vmbus_open expects this size to also
include vmbus packet header. This leads to 4096 bytes
dm_unballoon_request messages being truncated to 4080 bytes. When the
driver tries to read next packet it starts from a wrong read_index,
receives garbage and prints a lot of "Unhandled message: type:
<garbage>" in dmesg.
Allocate the buffer with HV_HYP_PAGE_SIZE more bytes to make room for
the header.
Fixes: adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer")
Suggested-by: Michael Kelley (LINUX) <mikelley@xxxxxxxxxxxxx>
Suggested-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
Signed-off-by: Yanming Liu <yanminglr@xxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Reviewed-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220119202052.3006981-1-yanminglr@xxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index ca873a3b98dbe..f2d05bff42453 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1660,6 +1660,13 @@ static int balloon_connect_vsp(struct hv_device *dev)
unsigned long t;
int ret;
+ /*
+ * max_pkt_size should be large enough for one vmbus packet header plus
+ * our receive buffer size. Hyper-V sends messages up to
+ * HV_HYP_PAGE_SIZE bytes long on balloon channel.
+ */
+ dev->channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
+
ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0,
balloon_onchannelcallback, dev);
if (ret)
