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@xxxxxxx>
>> ---
>> 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. ;-)
>
