From: Yanming Liu <redacted> Sent: Wednesday, January 19, 2022 12:14 PM

On Thu, Jan 20, 2022 at 2:12 AM Michael Kelley (LINUX)
[off-list ref] wrote:

quoted

From: Wei Liu <wei.liu@kernel.org> Sent: Friday, January 14, 2022 11:13 AM

quoted

On Mon, Jan 10, 2022 at 01:44:19AM +0100, Andrea Parri wrote:

quoted

(Extending Cc: list,)

On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote:

The VSS driver in hv_snapshot.c allocates a receive buffer of 8 Kbytes
and sets max_pkt_size to 8 Kbytes.  But the received messages are
all fixed size and small.  I don't know why the driver uses an 8 Kbyte
receive buffer instead of 4 Kbytes, but the current settings are
more than sufficient.

Well, I'm not sure, on August 2021 there was a patch changing
max_pkt_size to 8 KiB for VSS driver:
https://lore.kernel.org/linux-hyperv/20210825190217.qh2c6yq5qr3ntum5@liuwe-devbox-debian-v2/T/ (local)

The patch mentioned a 6304 bytes VSS message. Which is part of the
reason I tried to address the more "general" problem of potentially
mismatching buffer size.

This is certainly interesting.   The Linux driver is not processing
all those bytes, so I'm not sure what Hyper-V is passing to the
guest.  I'll check with the Hyper-V team to be sure.

Michael