selftests/mm: skip uffd-wp-mremap if UFFD write-protect is unsupported

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

Link: https://lore.kernel.org/c3c5af76d71d5f4446f773f4de94882efc33ebe4.1779296493.git.sayalip@linux.ibm.com
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/uffd-wp-mremap.c b/tools/testing/selftests/mm/uffd-wp-mremap.c
index 90ac410c6c6fb70546de6fafd72bcd4270c05561..c973d6722720c3afc66c5eabec5a810399adb400 100644 (file)
--- 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 unsigned long 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;
@@ -338,6 +349,8 @@ int main(int argc, char **argv)
 
        hugepage_save_settings(true, true);
 
+       check_uffd_wp_feature_supported();
+
        pagesize = getpagesize();
        nr_thpsizes = detect_thp_sizes(thpsizes, ARRAY_SIZE(thpsizes));
        nr_hugetlbsizes = hugetlb_setup(1, hugetlbsizes, ARRAY_SIZE(hugetlbsizes));