[PATCH v3 09/13] selftests/mm: skip uffd-wp-mremap if UFFD write-protect is unsupported

Sayali Patil
2026-03-27T07:18:02Z

The uffd-wp-mremap test requires the UFFD_FEATURE_PAGEFAULT_FLAG_WP
capability. On systems where userfaultfd write-protect is
not supported, uffd_register() fails and the test reports failures.

Check for the required feature at startup and skip the test when the
UFFD_FEATURE_PAGEFAULT_FLAG_WP capability is not present,
preventing false failures on unsupported configurations.

Before patch:
running ./uffd-wp-mremap
------------------------
[INFO] detected THP size: 256 KiB
[INFO] detected THP size: 512 KiB
[INFO] detected THP size: 1024 KiB
[INFO] detected THP size: 2048 KiB
[INFO] detected hugetlb page size: 2048 KiB
[INFO] detected hugetlb page size: 1048576 KiB
1..24
[RUN] test_one_folio(size=65536, private=false, swapout=false,
hugetlb=false)
not ok 1 uffd_register() failed
[RUN] test_one_folio(size=65536, private=true, swapout=false,
hugetlb=false)
not ok 2 uffd_register() failed
[RUN] test_one_folio(size=65536, private=false, swapout=true,
hugetlb=false)
not ok 3 uffd_register() failed
[RUN] test_one_folio(size=65536, private=true, swapout=true,
hugetlb=false)
not ok 4 uffd_register() failed
[RUN] test_one_folio(size=262144, private=false, swapout=false,
hugetlb=false)
not ok 5 uffd_register() failed
[RUN] test_one_folio(size=524288, private=false, swapout=false,
hugetlb=false)
not ok 6 uffd_register() failed
.
.
.
Bail out! 24 out of 24 tests failed
Totals: pass:0 fail:24 xfail:0 xpass:0 skip:0 error:0
[FAIL]
not ok 1 uffd-wp-mremap # exit=1

After patch:
running ./uffd-wp-mremap
------------------------
1..0 # SKIP uffd-wp feature not supported
[SKIP]
ok 1 uffd-wp-mremap # SKIP

Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
tools/testing/selftests/mm/uffd-wp-mremap.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/tools/testing/selftests/mm/uffd-wp-mremap.c b/tools/testing/selftests/mm/uffd-wp-mremap.c
index 17186d4a4147..6edbd09f0ca6 100644
--- a/tools/testing/selftests/mm/uffd-wp-mremap.c
+++ b/tools/testing/selftests/mm/uffd-wp-mremap.c
@@ -19,6 +19,17 @@ static size_t thpsizes[20];
static int nr_hugetlbsizes;
static size_t hugetlbsizes[10];

+static void check_uffd_wp_feature_supported(void)
+{
+ uint64_t features;
+
+ if (uffd_get_features(&features) && errno == ENOENT)
+ ksft_exit_skip("failed to get available features (%d)\n", errno);
+
+ if (!(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP))
+ ksft_exit_skip("uffd-wp feature not supported\n");
+}
+
static int detect_thp_sizes(size_t sizes[], int max)
{
int count = 0;
@@ -336,6 +347,8 @@ int main(int argc, char **argv)
struct thp_settings settings;
int i, j, plan = 0;

+ check_uffd_wp_feature_supported();
+
pagesize = getpagesize();
nr_thpsizes = detect_thp_sizes(thpsizes, ARRAY_SIZE(thpsizes));
nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,
--
2.52.0