Re: [PATCH v1 3/9] selftests/mm: Skip soft-dirty tests on arm64

[David Hildenbrand <david@redhat.com>]

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@arm.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