linux-kernel - Re: [PATCH v7 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6

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Date: Mon, 12 Feb 2024 16:14:49 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Charlie Jenkins <charlie@...osinc.com>,
 David Laight <David.Laight@...lab.com>, Palmer Dabbelt <palmer@...belt.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Al Viro <viro@...iv.linux.org.uk>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/2] lib: checksum: Use aligned accesses for
 ip_fast_csum and csum_ipv6_magic tests

On 2/12/24 12:33, Charlie Jenkins wrote:
> The test cases for ip_fast_csum and csum_ipv6_magic were failing on a
> variety of architectures that are big endian or do not support
> misalgined accesses. Both of these test cases are changed to support big
> and little endian architectures.
> 
> The test for ip_fast_csum is changed to align the data along (14 +
> NET_IP_ALIGN) bytes which is the alignment of an IP header. The test for
> csum_ipv6_magic aligns the data using a struct. An extra padding field
> is added to the struct to ensure that the size of the struct is the same
> on all architectures (44 bytes).
> 
> Fixes: 6f4c45cbcb00 ("kunit: Add tests for csum_ipv6_magic and ip_fast_csum")
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>

This thing really wants to annoy me. Now I get:

      # test_csum_ipv6_magic: ASSERTION FAILED at lib/checksum_kunit.c:494
      Expected ( u64)csum_result == ( u64)expected, but
          ( u64)csum_result == 46543 (0xb5cf)
          ( u64)expected == 46544 (0xb5d0)
      not ok 5 test_csum_ipv6_magic

with the parisc64 tests. All other architectures / platforms work fine
after applying the various pending fixes. It looks like a carry gets
lost somewhere, but I have not been able to figure out where exactly
that happens. This only happens with the 64-bit hppa assembler code.

Guenter