Re: [PATCH v11] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6_magic tests

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


On 2/29/24 14:46, Charlie Jenkins wrote:
The test cases for ip_fast_csum and csum_ipv6_magic were not properly
aligning the IP header, which were causing failures on architectures
that do not support misaligned accesses like some ARM platforms. To
solve this, align the data along (14 + NET_IP_ALIGN) bytes which is the
standard alignment of an IP header and must be supported by the

Furthermore, all architectures except the m68k pad "struct
csum_ipv6_magic_data" to 44 bytes. To make compatible with the m68k,
manually pad this structure to 44 bytes.

Fixes: 6f4c45cbcb00 ("kunit: Add tests for csum_ipv6_magic and ip_fast_csum")
Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
The ip_fast_csum and csum_ipv6_magic tests did not work on all
architectures due to differences in misaligned access support.
Fix those issues by changing endianness of data and aligning the data.

This patch relies upon a patch from Christophe:

[PATCH net] kunit: Fix again checksum tests on big endian CPUs

Various test results:

On v6.8-rc6-120-g87adedeba51a (current mainline), without this patch

- mps2-an385:mps2_defconfig crashes in IPv6 checksum tests
- ipv6 checksum tests fail on parisc, parisc64, sh, and sheb.

The previously seen problems on big endian systems are still seen with
v6.8-rc6, but are gone after commit 3d6423ef8d51 ("kunit: Fix again
checksum tests on big endian CPUs") has been applied upstream. This includes
the test failures seen with m68k.

The parisc/parisc64 test failures are independent of this patch. Fixes are
available in linux-next and pending in qemu. The sh/sheb failures are due
to upstream commit cadc4e1a2b4 and are no longer seen after reverting that

This leaves the mps2-an385:mps2_defconfig crash, which is avoided by this patch.
My understanding, which may be wrong, is that arm images with thumb instructions
do not support unaligned accesses (maybe I should say do not support unaligned
accesses with the mps2-an385 qemu emulation; I did not test with real hardware,
after all).

Given all that, the continued discussion around the subject, and the lack
of agreement if unaligned accesses should be tested or not, I don't really
see a path forward for this patch. The remaining known problem is arm with
thumb instructions. I don't think that is going to be fixed. I suspect that
no one but me even tries to run that code (or any arm:nommu images, for that
matter). I'd suggest to drop this patch, and I'll stop testing IP checksum
generation for mps2-an385:mps2_defconfig.

Sorry for all the noise this has generated.


[Index of Archives]     [Linux SoC]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux