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Date: Thu, 13 Jul 2023 16:09:13 +0200
From: David Hildenbrand <david@...hat.com>
To: Ryan Roberts <ryan.roberts@....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 13.07.23 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;
+
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)
--
Cheers,
David / dhildenb
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