[PATCH v4 11/15] selftests/mm: skip uffd-wp-mremap if UFFD write-protect is unsupported

[Sayali Patil <sayalip@linux.ibm.com>]

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

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..8f288484d5f5 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 = 0;
+
+	if (uffd_get_features(&features))
+		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