Re: [PATCH v10] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6_magic tests

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On 2/28/24 02:15, Geert Uytterhoeven wrote:
CC testing

On Wed, Feb 28, 2024 at 8:59 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 2/27/24 23:25, Christophe Leroy wrote:
[ ... ]

This test case is supposed to be as true to the "general case" as
possible, so I have aligned the data along 14 + NET_IP_ALIGN. On ARM
this will be a 16-byte boundary since NET_IP_ALIGN is 2. A driver that
does not follow this may not be appropriately tested by this test case,
but anyone is welcome to submit additional test cases that address this
additional alignment concern.

But then this test case is becoming less and less true to the "general
case" with this patch, whereas your initial implementation was almost
perfect as it was covering most cases, a lot more than what we get with
that patch applied.

NP with me if that is where people want to go. I'll simply disable checksum
tests on all architectures which don't support unaligned accesses (so far
it looks like that is only arm with thumb instructions, and possibly nios2).
I personally find that less desirable and would have preferred a second
configurable set of tests for unaligned accesses, but I have no problem
with it.

IMHO the tests should validate the expected functionality.  If a test
fails, either functionality is missing or behaves wrong, or the test
is wrong.

What is the point of writing tests for a core functionality like network
checksumming that do not match the expected functionality?

Tough one. I can't enable CONFIG_NET_TEST on nios2, parisc, and arm with THUMB
enabled due to crashes or hangs in gso tests. I accept that. Downside is that I
have to disable CONFIG_NET_TEST on those architectures/platforms entirely,
meaning a whole class of tests are missing for those architectures. I would
prefer to have a configuration option such as CONFIG_NET_GSO_TEST to let me
disable the problematic tests for the affected platforms so I can run all
the other network unit tests. Yes, obviously something is wrong either with
the affected tests or with the implementation of the tested functionality
on the affected systems, but that could be handled separately if a separate
configuration option existed, and new regressions in other tests on the affected
architectures could be identified as they happen.

This case is similar. I'd prefer to have a separate configuration option,
say, CONFIG_CHECKSUM_MISALIGNED_KUNIT, which I can disable to be able to
run the common checksum tests on platforms / architectures which don't
support unaligned accesses.

However, as I said, if the community wants to take a harsh stance, I have no
problem with just disabling groups of tests entirely on platforms which have
a problem with part of it.


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