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Message-ID: <556d05f0-7103-1079-fce1-1fb6bd40b17c@arm.com>
Date: Thu, 13 Jul 2023 15:14:07 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: David Hildenbrand <david@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Shuah Khan <shuah@...nel.org>,
Jérôme Glisse <jglisse@...hat.com>,
Mark Brown <broonie@...nel.org>,
John Hubbard <jhubbard@...dia.com>,
Florent Revest <revest@...omium.org>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v1 3/9] selftests/mm: Skip soft-dirty tests on arm64
On 13/07/2023 15:09, David Hildenbrand wrote:
> On 13.07.23 16:03, Ryan Roberts wrote:
>> On 13/07/2023 14:56, David Hildenbrand wrote:
>>> On 13.07.23 15:54, Ryan Roberts wrote:
>>>> arm64 does not support the soft-dirty PTE bit. However there are tests
>>>> in `madv_populate` and `soft-dirty` which assume it is supported and
>>>> cause spurious failures to be reported when preferred behaviour would be
>>>> to mark the tests as skipped.
>>>>
>>>> Unfortunately, the only way to determine if the soft-dirty dirty bit is
>>>> supported is to write to a page, then see if the bit is set in
>>>> /proc/self/pagemap. But the tests that we want to conditionally execute
>>>> are testing precicesly this. So if we introduced this feature check, we
>>>> could accedentally turn a real failure (on a system that claims to
>>>> support soft-dirty) into a skip.
>>>>
>>>> So instead, do the check based on architecture; for arm64, we report
>>>> that soft-dirty is not supported. This is wrapped up into a utility
>>>> function `system_has_softdirty()`, which is used to skip the whole
>>>> `soft-dirty` suite, and mark the soft-dirty tests in the `madv_populate`
>>>> suite as skipped.
>>>>
>>>> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
>>>> ---
>>>> tools/testing/selftests/mm/madv_populate.c | 18 +++++++++++++-----
>>>> tools/testing/selftests/mm/soft-dirty.c | 3 +++
>>>> tools/testing/selftests/mm/vm_util.c | 17 +++++++++++++++++
>>>> tools/testing/selftests/mm/vm_util.h | 1 +
>>>> 4 files changed, 34 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/tools/testing/selftests/mm/madv_populate.c
>>>> b/tools/testing/selftests/mm/madv_populate.c
>>>> index 60547245e479..5a8c176d7fec 100644
>>>> --- a/tools/testing/selftests/mm/madv_populate.c
>>>> +++ b/tools/testing/selftests/mm/madv_populate.c
>>>> @@ -232,6 +232,14 @@ static bool range_is_not_softdirty(char *start, ssize_t
>>>> size)
>>>> return ret;
>>>> }
>>>>
>>>> +#define ksft_test_result_if_softdirty(cond, ...) \
>>>> +do { \
>>>> + if (system_has_softdirty()) \
>>>> + ksft_test_result(cond, __VA_ARGS__); \
>>>> + else \
>>>> + ksft_test_result_skip(__VA_ARGS__); \
>>>> +} while (0)
>>>> +
>>>> static void test_softdirty(void)
>>>> {
>>>> char *addr;
>>>> @@ -246,19 +254,19 @@ static void test_softdirty(void)
>>>>
>>>> /* Clear any softdirty bits. */
>>>> clear_softdirty();
>>>> - ksft_test_result(range_is_not_softdirty(addr, SIZE),
>>>> + ksft_test_result_if_softdirty(range_is_not_softdirty(addr, SIZE),
>>>> "range is not softdirty\n");
>>>>
>>>> /* Populating READ should set softdirty. */
>>>> ret = madvise(addr, SIZE, MADV_POPULATE_READ);
>>>> - ksft_test_result(!ret, "MADV_POPULATE_READ\n");
>>>> - ksft_test_result(range_is_not_softdirty(addr, SIZE),
>>>> + ksft_test_result_if_softdirty(!ret, "MADV_POPULATE_READ\n");
>>>> + ksft_test_result_if_softdirty(range_is_not_softdirty(addr, SIZE),
>>>> "range is not softdirty\n");
>>>>
>>>> /* Populating WRITE should set softdirty. */
>>>> ret = madvise(addr, SIZE, MADV_POPULATE_WRITE);
>>>> - ksft_test_result(!ret, "MADV_POPULATE_WRITE\n");
>>>> - ksft_test_result(range_is_softdirty(addr, SIZE),
>>>> + ksft_test_result_if_softdirty(!ret, "MADV_POPULATE_WRITE\n");
>>>> + ksft_test_result_if_softdirty(range_is_softdirty(addr, SIZE),
>>>> "range is softdirty\n");
>>>
>>> We probably want to skip the whole test_*softdirty* test instead of adding this
>>> (IMHO suboptimal) ksft_test_result_if_softdirty.
>>
>> Yeah I thought about doing it that way, but then the output just looks like
>> there were fewer tests and they all passed. But thinking about it now, I guess
>> the TAP header outputs the number of planned tests and the number of tests
>> executed are fewer, so a machine parser would still notice. I just don't like
>> that it outputs skipped:0.
>>
>> But it a lightly held view. Happy to just do:
>>
>> if (system_has_softdirty())
>> test_softdirty()
>>
>> If you insist. ;-)
>
> diff --git a/tools/testing/selftests/mm/madv_populate.c
> b/tools/testing/selftests/mm/madv_populate.c
> index 60547245e479..33fda0337b32 100644
> --- a/tools/testing/selftests/mm/madv_populate.c
> +++ b/tools/testing/selftests/mm/madv_populate.c
> @@ -266,12 +266,16 @@ static void test_softdirty(void)
>
> int main(int argc, char **argv)
> {
> + int nr_tests = 16;
> int err;
>
> pagesize = getpagesize();
>
> + if (system_has_softdirty())
> + nr_tests += 5;
This is the opposite of the point I was trying to make; If there are 21 tests in
a suite, I'd like to know that there are 21 tests, 16 of which passed and 5 of
which were skipped. This will hide the 5 from the test report.
> +
> ksft_print_header();
> - ksft_set_plan(21);
> + ksft_set_plan(nr_tests);
>
> sense_support();
> test_prot_read();
> @@ -279,7 +283,8 @@ int main(int argc, char **argv)
> test_holes();
> test_populate_read();
> test_populate_write();
> - test_softdirty();
> + if (system_has_softdirty())
> + test_softdirty();
>
> err = ksft_get_fail_cnt();
> if (err)
>
>
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