John Hubbard 53ebbfdd0e net: mvvp2: fix short frame size on s390
[ Upstream commit 704e624f7b3e8a4fc1ce43fb564746d1d07b20c0 ]

On s390, the following build warning occurs:

drivers/net/ethernet/marvell/mvpp2/mvpp2.h:844:2: warning: overflow in
conversion from 'long unsigned int' to 'int' changes value from
'18446744073709551584' to '-32' [-Woverflow]
844 |  ((total_size) - MVPP2_SKB_HEADROOM - MVPP2_SKB_SHINFO_SIZE)

This happens because MVPP2_SKB_SHINFO_SIZE, which is 320 bytes (which is
already 64-byte aligned) on some architectures, actually gets ALIGN'd up
to 512 bytes in the s390 case.

So then, when this is invoked:

    MVPP2_RX_MAX_PKT_SIZE(MVPP2_BM_SHORT_FRAME_SIZE)

...that turns into:

     704 - 224 - 512 == -32

...which is not a good frame size to end up with! The warning above is a
bit lucky: it notices a signed/unsigned bad behavior here, which leads
to the real problem of a frame that is too short for its contents.

Increase MVPP2_BM_SHORT_FRAME_SIZE by 32 (from 704 to 736), which is
just exactly big enough. (The other values can't readily be changed
without causing a lot of other problems.)

Fixes: 07dd0a7aae7f ("mvpp2: add basic XDP support")
Cc: Sven Auhagen <sven.auhagen@voleatech.de>
Cc: Matteo Croce <mcroce@microsoft.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-08-18 08:59:09 +02:00
2020-10-17 11:18:18 -07:00
2021-08-15 14:00:27 +02:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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