selftests/mm: skip guard_regions.uffd tests when uffd is not present

Patch series "Skip mm selftests instead when kernel features are not
present", v2.

Two guard_regions tests on userfaultfd fail when userfaultfd is not
present.  Skip them instead.

hugevm test reads kernel config to get page table level information and
fails when neither /proc/config.gz nor /boot/config-* is present.  Skip it
instead.

This patch (of 2):

When userfaultfd is not compiled into kernel, userfaultfd() returns -1,
causing guard_regions.uffd tests to fail.  Skip the tests instead.

Link: https://lkml.kernel.org/r/20250516132938.356627-1-ziy@nvidia.com
Link: https://lkml.kernel.org/r/20250516132938.356627-2-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Adam Sindelar <adam@wowsignal.io>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
index 0cd9d23..93af3d3 100644 (file)
--- a/tools/testing/selftests/mm/guard-regions.c
+++ b/tools/testing/selftests/mm/guard-regions.c
@@ -1453,8 +1453,21 @@ TEST_F(guard_regions, uffd)
 
        /* Set up uffd. */
        uffd = userfaultfd(0);
-       if (uffd == -1 && errno == EPERM)
-               ksft_exit_skip("No userfaultfd permissions, try running as root.\n");
+       if (uffd == -1) {
+               switch (errno) {
+               case EPERM:
+                       SKIP(return, "No userfaultfd permissions, try running as root.");
+                       break;
+               case ENOSYS:
+                       SKIP(return, "userfaultfd is not supported/not enabled.");
+                       break;
+               default:
+                       ksft_exit_fail_msg("userfaultfd failed with %s\n",
+                                          strerror(errno));
+                       break;
+               }
+       }
+
        ASSERT_NE(uffd, -1);
 
        ASSERT_EQ(ioctl(uffd, UFFDIO_API, &api), 0);