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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: p4mto9rtmxn1xrn8k51srzq5eztqyefw X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6CBC0A0013 X-HE-Tag: 1750778285-482869 X-HE-Meta: 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 I94kTRmT 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 24.06.25 06:24, Li Wang wrote: > The current implementation of test_unmerge_uffd_wp() explicitly sets > `uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP` before calling > UFFDIO_API. This can cause the ioctl() call to fail with EINVAL on kernels > that do not support UFFD-WP, leading the test to fail unnecessarily: > > # ------------------------------ > # running ./ksm_functional_tests > # ------------------------------ > # TAP version 13 > # 1..9 > # # [RUN] test_unmerge > # ok 1 Pages were unmerged > # # [RUN] test_unmerge_zero_pages > # ok 2 KSM zero pages were unmerged > # # [RUN] test_unmerge_discarded > # ok 3 Pages were unmerged > # # [RUN] test_unmerge_uffd_wp > # not ok 4 UFFDIO_API failed <----- > # # [RUN] test_prot_none > # ok 5 Pages were unmerged > # # [RUN] test_prctl > # ok 6 Setting/clearing PR_SET_MEMORY_MERGE works > # # [RUN] test_prctl_fork > # # No pages got merged > # # [RUN] test_prctl_fork_exec > # ok 7 PR_SET_MEMORY_MERGE value is inherited > # # [RUN] test_prctl_unmerge > # ok 8 Pages were unmerged > # Bail out! 1 out of 8 tests failed > # # Planned tests != run tests (9 != 8) > # # Totals: pass:7 fail:1 xfail:0 xpass:0 skip:0 error:0 > # [FAIL] > > This patch improves compatibility and robustness of the UFFD-WP test > (test_unmerge_uffd_wp) by correctly implementing the UFFDIO_API > two-step handshake as recommended by the userfaultfd(2) man page. > > Key changes: > > 1. Use features=0 in the initial UFFDIO_API call to query supported > feature bits, rather than immediately requesting WP support. > > 2. Skip the test gracefully if: > - UFFDIO_API fails with EINVAL (e.g. unsupported API version), or > - UFFD_FEATURE_PAGEFAULT_FLAG_WP is not advertised by the kernel. > > 3. Close the initial userfaultfd and create a new one before enabling > the required feature, since UFFDIO_API can only be called once per fd. > > 4. Improve diagnostics by distinguishing between expected and unexpected > failures, using strerror() to report errors. > > This ensures the test behaves correctly across a wider range of kernel > versions and configurations, while preserving the intended behavior on > kernels that support UFFD-WP. > > Suggestted-by: David Hildenbrand > Signed-off-by: Li Wang > Cc: Aruna Ramakrishna > Cc: Bagas Sanjaya > Cc: Catalin Marinas > Cc: Dave Hansen > Cc: Joey Gouly > Cc: Johannes Weiner > Cc: Keith Lucas > Cc: Ryan Roberts > Cc: Shuah Khan > --- > > Notes: > v1 --> v2: > * Close the original userfaultfd and open a new one before enabling features > * Reworked UFFDIO_API negotiation to follow the official two-step handshake > > .../selftests/mm/ksm_functional_tests.c | 28 +++++++++++++++++-- > 1 file changed, 26 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c > index b61803e36d1c..19e5b741893a 100644 > --- a/tools/testing/selftests/mm/ksm_functional_tests.c > +++ b/tools/testing/selftests/mm/ksm_functional_tests.c > @@ -393,9 +393,13 @@ static void test_unmerge_uffd_wp(void) > > /* See if UFFD-WP is around. */ > uffdio_api.api = UFFD_API; > - uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP; > + uffdio_api.features = 0; > if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) { > - ksft_test_result_fail("UFFDIO_API failed\n"); > + if (errno == EINVAL) > + ksft_test_result_skip("The API version requested is not supported\n"); > + else > + ksft_test_result_fail("UFFDIO_API failed: %s\n", strerror(errno)); > + > goto close_uffd; > } > if (!(uffdio_api.features & UFFD_FEATURE_PAGEFAULT_FLAG_WP)) { > @@ -403,6 +407,26 @@ static void test_unmerge_uffd_wp(void) > goto close_uffd; > } > > + /* > + * UFFDIO_API must only be called once to enable features. > + * So we close the old userfaultfd and create a new one to > + * actually enable UFFD_FEATURE_PAGEFAULT_FLAG_WP. > + */ > + close(uffd); > + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); > + if (uffd < 0) { > + ksft_test_result_skip("__NR_userfaultfd failed\n"); If it now suddenly fails (after it working above), this sure is a fail, right? Apart from that Acked-by: David Hildenbrand -- Cheers, David / dhildenb