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Message-ID: <99dead0d-08e2-ab1c-46dc-d3f4f97a71e8@redhat.com>
Date: Mon, 17 Jul 2023 19:20:30 +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>,
Peter Xu <peterx@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 2/8] selftests/mm: Skip soft-dirty tests on arm64
On 17.07.23 12:31, Ryan Roberts wrote:
> arm64 does not support the soft-dirty PTE bit. However, the `soft-dirty`
> test suite is currently run unconditionally and therefore generates
> spurious test failures on arm64. There are also some tests in
> `madv_populate` which assume it is supported.
>
> For `soft-dirty` lets disable the whole suite for arm64; it is no longer
> built and run_vmtests.sh will skip it if its not present.
>
> For `madv_populate`, we need a runtime mechanism so that the remaining
> tests continue to be run. 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.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
> tools/testing/selftests/mm/Makefile | 5 ++++-
> tools/testing/selftests/mm/madv_populate.c | 26 ++++++++++++++++++++--
> tools/testing/selftests/mm/run_vmtests.sh | 5 ++++-
> 3 files changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index 66d7c07dc177..3514697fc2db 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -63,12 +63,15 @@ TEST_GEN_PROGS += thuge-gen
> TEST_GEN_PROGS += transhuge-stress
> TEST_GEN_PROGS += uffd-stress
> TEST_GEN_PROGS += uffd-unit-tests
> -TEST_GEN_PROGS += soft-dirty
> TEST_GEN_PROGS += split_huge_page_test
> TEST_GEN_PROGS += ksm_tests
> TEST_GEN_PROGS += ksm_functional_tests
> TEST_GEN_PROGS += mdwe_test
>
> +ifneq ($(ARCH),arm64)
> +TEST_GEN_PROGS += soft-dirty
> +endif
> +
> ifeq ($(ARCH),x86_64)
> CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh "$(CC)" ../x86/trivial_32bit_program.c -m32)
> CAN_BUILD_X86_64 := $(shell ./../x86/check_cc.sh "$(CC)" ../x86/trivial_64bit_program.c)
> diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c
> index 60547245e479..17bcb07f19f3 100644
> --- a/tools/testing/selftests/mm/madv_populate.c
> +++ b/tools/testing/selftests/mm/madv_populate.c
> @@ -264,14 +264,35 @@ static void test_softdirty(void)
> munmap(addr, SIZE);
> }
>
> +static int system_has_softdirty(void)
> +{
> + /*
> + * There is no way to check if the kernel supports soft-dirty, other
> + * than by writing to a page and seeing if the bit was set. But the
> + * tests are intended to check that the bit gets set when it should, so
> + * doing that check would turn a potentially legitimate fail into a
> + * skip. Fortunately, we know for sure that arm64 does not support
> + * soft-dirty. So for now, let's just use the arch as a corse guide.
> + */
> +#if defined(__aarch64__)
> + return 0;
> +#else
> + return 1;
> +#endif
> +}
I guess that will also make the compiler remove any traces of
test_softdirty()( from the binary.
Acked-by: David Hildenbrand <david@...hat.com>
--
Cheers,
David / dhildenb
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