Re: [PATCH v1 2/3] selftests/ksm: ksm_functional_tests: add prctl unmerge test

David Hildenbrand david@redhat.com writes:

Let's test whether setting PR_SET_MEMORY_MERGE to 0 after setting it to 1 will unmerge pages, similar to how setting MADV_UNMERGEABLE after setting MADV_MERGEABLE would.

Signed-off-by: David Hildenbrand david@redhat.com

.../selftests/mm/ksm_functional_tests.c | 46 ++++++++++++++++--- 1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c index 7bc9fc17c9f0..26853badae70 100644 --- a/tools/testing/selftests/mm/ksm_functional_tests.c +++ b/tools/testing/selftests/mm/ksm_functional_tests.c @@ -91,9 +91,10 @@ static int ksm_merge(void) return 0; }

-static char *mmap_and_merge_range(char val, unsigned long size) +static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl) { char *map;

• int ret;

  map = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);

@@ -110,7 +111,17 @@ static char *mmap_and_merge_range(char val, unsigned long size)

/* Make sure each page contains the same values to merge them. */ memset(map, val, size);

• if (madvise(map, size, MADV_MERGEABLE)) {

• if (use_prctl) {

• ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
  

• if (ret < 0 && errno == EINVAL) {
  

• 	ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
  

• 	goto unmap;
  

• } else if (ret) {
  

• 	ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
  

• 	goto unmap;
  

• }
  

• } else if (madvise(map, size, MADV_MERGEABLE)) { ksft_test_result_fail("MADV_MERGEABLE failed\n"); goto unmap; }

@@ -133,7 +144,7 @@ static void test_unmerge(void)

ksft_print_msg("[RUN] %s\n", __func__);

• map = mmap_and_merge_range(0xcf, size);

• map = mmap_and_merge_range(0xcf, size, false); if (map == MAP_FAILED) return;

@@ -155,7 +166,7 @@ static void test_unmerge_discarded(void)

ksft_print_msg("[RUN] %s\n", __func__);

• map = mmap_and_merge_range(0xcf, size);

• map = mmap_and_merge_range(0xcf, size, false); if (map == MAP_FAILED) return;

@@ -187,7 +198,7 @@ static void test_unmerge_uffd_wp(void)

ksft_print_msg("[RUN] %s\n", __func__);

• map = mmap_and_merge_range(0xcf, size);

• map = mmap_and_merge_range(0xcf, size, false); if (map == MAP_FAILED) return;

@@ -323,9 +334,31 @@ static void test_prctl_fork(void) ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n"); }

+static void test_prctl_unmerge(void) +{

• const unsigned int size = 2 * MiB;
• char *map;
• ksft_print_msg("[RUN] %s\n", __func__);
• map = mmap_and_merge_range(0xcf, size, true);
• if (map == MAP_FAILED)

• return;
  

• if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {

• ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
  

• goto unmap;
  

• }
• ksft_test_result(!range_maps_duplicates(map, size),

• 	 "Pages were unmerged\n");
  

+unmap:

• munmap(map, size);

+}

int main(int argc, char **argv) {

• unsigned int tests = 4;

• unsigned int tests = 5; int err;

#ifdef __NR_userfaultfd @@ -355,6 +388,7 @@ int main(int argc, char **argv)

test_prctl(); test_prctl_fork();

• test_prctl_unmerge();

  err = ksft_get_fail_cnt(); if (err)

Acked-by: Stefan Roesch shr@devkernel.io