[PATCH 23/29] selftests/mm: Move uffd minor test to unit test

Peter Xu
2023-03-30T16:10:38Z

This moves the minor test to the new unit test.

Rewrite the content check with char* opeartions to avoid fiddling with
my_bcmp().

Drop global vars test_uffdio_minor and test_collapse, just assume test them
always in common code for now.

OTOH make this single test into five tests:

- minor test on [shmem, hugetlb] with wp=false
- minor test on [shmem, hugetlb] with wp=true
- minor test + collapse on shmem only

One thing to mention that we used to test COLLAPSE+WP but that doesn't
sound right at all. It's possible it's silently broken but unnoticed
because COLLAPSE is not part of the default test suite.

Make the MADV_COLLAPSE test fail-able (by skip it when failing), because
it's not guaranteed to success anyway.

Drop a bunch of useless code after the move, because the unit test always
use aligned num of pages and has nothing to do with n_cpus.

Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
tools/testing/selftests/mm/uffd-common.c | 25 ++--
tools/testing/selftests/mm/uffd-common.h | 4 +-
tools/testing/selftests/mm/uffd-stress.c | 131 +------------------
tools/testing/selftests/mm/uffd-unit-tests.c | 120 +++++++++++++++++
4 files changed, 135 insertions(+), 145 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
index ae6b61144b53..95ad619d0df4 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -13,8 +13,8 @@ volatile bool test_uffdio_copy_eexist = true;
unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
int uffd = -1, uffd_flags, finished, *pipefd, test_type;
-bool map_shared, test_collapse, test_dev_userfaultfd;
-bool test_uffdio_wp = true, test_uffdio_minor = false;
+bool map_shared, test_dev_userfaultfd;
+bool test_uffdio_wp = true;
unsigned long long *count_verify;
uffd_test_ops_t *uffd_test_ops;

@@ -126,28 +126,27 @@ static int shmem_allocate_area(void **alloc_area, bool is_src)
char *p = NULL, *p_alias = NULL;
int mem_fd = uffd_mem_fd_create(bytes * 2, false);

- if (test_collapse) {
- p = BASE_PMD_ADDR;
- if (!is_src)
- /* src map + alias + interleaved hpages */
- p += 2 * (bytes + hpage_size);
- p_alias = p;
- p_alias += bytes;
- p_alias += hpage_size; /* Prevent src/dst VMA merge */
- }
+ /* TODO: clean this up. Use a static addr is ugly */
+ p = BASE_PMD_ADDR;
+ if (!is_src)
+ /* src map + alias + interleaved hpages */
+ p += 2 * (bytes + hpage_size);
+ p_alias = p;
+ p_alias += bytes;
+ p_alias += hpage_size; /* Prevent src/dst VMA merge */

*alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
if (*alloc_area == MAP_FAILED)
err("mmap of memfd failed");
- if (test_collapse && *alloc_area != p)
+ if (*alloc_area != p)
err("mmap of memfd failed at %p", p);

area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
if (area_alias == MAP_FAILED)
err("mmap of memfd alias failed");
- if (test_collapse && area_alias != p_alias)
+ if (area_alias != p_alias)
err("mmap of anonymous memory failed at %p", p_alias);

if (is_src)
diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h
index 51ec75f6d0c1..16d32ddf8412 100644
--- a/tools/testing/selftests/mm/uffd-common.h
+++ b/tools/testing/selftests/mm/uffd-common.h
@@ -90,8 +90,8 @@ typedef struct uffd_test_ops uffd_test_ops_t;
extern unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
extern char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
extern int uffd, uffd_flags, finished, *pipefd, test_type;
-extern bool map_shared, test_collapse, test_dev_userfaultfd;
-extern bool test_uffdio_wp, test_uffdio_minor;
+extern bool map_shared, test_dev_userfaultfd;
+extern bool test_uffdio_wp;
extern unsigned long long *count_verify;
extern volatile bool test_uffdio_copy_eexist;

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index 50738a993afc..49fa61e5c54a 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -52,8 +52,6 @@ pthread_attr_t attr;
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)

-#define factor_of_2(x) ((x) ^ ((x) & ((x) - 1)))
-
const char *examples =
"# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
"./userfaultfd anon 100 99999\n\n"
@@ -79,8 +77,6 @@ static void usage(void)
"Supported mods:\n");
fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
- fprintf(stderr, "\tcollapse - Test MADV_COLLAPSE of UFFDIO_REGISTER_MODE_MINOR\n"
- "memory\n");
fprintf(stderr, "\nExample test mod usage:\n");
fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
@@ -585,92 +581,6 @@ static int userfaultfd_sig_test(void)
return userfaults != 0;
}

-void check_memory_contents(char *p)
-{
- unsigned long i;
- uint8_t expected_byte;
- void *expected_page;
-
- if (posix_memalign(&expected_page, page_size, page_size))
- err("out of memory");
-
- for (i = 0; i < nr_pages; ++i) {
- expected_byte = ~((uint8_t)(i % ((uint8_t)-1)));
- memset(expected_page, expected_byte, page_size);
- if (my_bcmp(expected_page, p + (i * page_size), page_size))
- err("unexpected page contents after minor fault");
- }
-
- free(expected_page);
-}
-
-static int userfaultfd_minor_test(void)
-{
- unsigned long p;
- pthread_t uffd_mon;
- char c;
- struct uffd_stats stats = { 0 };
-
- if (!test_uffdio_minor)
- return 0;
-
- printf("testing minor faults: ");
- fflush(stdout);
-
- uffd_test_ctx_init(uffd_minor_feature());
-
- if (uffd_register(uffd, area_dst_alias, nr_pages * page_size,
- false, test_uffdio_wp, true))
- err("register failure");
-
- /*
- * After registering with UFFD, populate the non-UFFD-registered side of
- * the shared mapping. This should *not* trigger any UFFD minor faults.
- */
- for (p = 0; p < nr_pages; ++p) {
- memset(area_dst + (p * page_size), p % ((uint8_t)-1),
- page_size);
- }
-
- stats.apply_wp = test_uffdio_wp;
- if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
- err("uffd_poll_thread create");
-
- /*
- * Read each of the pages back using the UFFD-registered mapping. We
- * expect that the first time we touch a page, it will result in a minor
- * fault. uffd_poll_thread will resolve the fault by bit-flipping the
- * page's contents, and then issuing a CONTINUE ioctl.
- */
- check_memory_contents(area_dst_alias);
-
- if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
- err("pipe write");
- if (pthread_join(uffd_mon, NULL))
- return 1;
-
- uffd_stats_report(&stats, 1);
-
- if (test_collapse) {
- printf("testing collapse of uffd memory into PMD-mapped THPs:");
- if (madvise(area_dst_alias, nr_pages * page_size,
- MADV_COLLAPSE))
- err("madvise(MADV_COLLAPSE)");
-
- uffd_test_ops->check_pmd_mapping(area_dst,
- nr_pages * page_size /
- read_pmd_pagesize());
- /*
- * This won't cause uffd-fault - it purely just makes sure there
- * was no corruption.
- */
- check_memory_contents(area_dst_alias);
- printf(" done.\n");
- }
-
- return stats.missing_faults != 0 || stats.minor_faults != nr_pages;
-}
-
static int userfaultfd_stress(void)
{
void *area;
@@ -783,7 +693,7 @@ static int userfaultfd_stress(void)
}

return userfaultfd_zeropage_test() || userfaultfd_sig_test()
- || userfaultfd_events_test() || userfaultfd_minor_test();
+ || userfaultfd_events_test();
}

static void set_test_type(const char *type)
@@ -798,13 +708,10 @@ static void set_test_type(const char *type)
map_shared = true;
test_type = TEST_HUGETLB;
uffd_test_ops = &hugetlb_uffd_test_ops;
- /* Minor faults require shared hugetlb; only enable here. */
- test_uffdio_minor = true;
} else if (!strcmp(type, "shmem")) {
map_shared = true;
test_type = TEST_SHMEM;
uffd_test_ops = &shmem_uffd_test_ops;
- test_uffdio_minor = true;
}
}

@@ -822,8 +729,6 @@ static void parse_test_type_arg(const char *raw_type)
test_dev_userfaultfd = true;
else if (!strcmp(token, "syscall"))
test_dev_userfaultfd = false;
- else if (!strcmp(token, "collapse"))
- test_collapse = true;
else
err("unrecognized test mod '%s'", token);
}
@@ -831,9 +736,6 @@ static void parse_test_type_arg(const char *raw_type)
if (!test_type)
err("failed to parse test type argument: '%s'", raw_type);

- if (test_collapse && test_type != TEST_SHMEM)
- err("Unsupported test: %s", raw_type);
-
if (test_type == TEST_HUGETLB)
page_size = default_huge_page_size();
else
@@ -855,8 +757,6 @@ static void parse_test_type_arg(const char *raw_type)

test_uffdio_wp = test_uffdio_wp &&
(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
- test_uffdio_minor = test_uffdio_minor &&
- (features & uffd_minor_feature());

close(uffd);
uffd = -1;
@@ -873,7 +773,6 @@ static void sigalrm(int sig)
int main(int argc, char **argv)
{
size_t bytes;
- size_t hpage_size = read_pmd_pagesize();

if (argc < 4)
usage();
@@ -885,36 +784,8 @@ int main(int argc, char **argv)
parse_test_type_arg(argv[1]);
bytes = atol(argv[2]) * 1024 * 1024;

- if (test_collapse && bytes & (hpage_size - 1))
- err("MiB must be multiple of %lu if :collapse mod set",
- hpage_size >> 20);
-
nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);

- if (test_collapse) {
- /* nr_cpus must divide (bytes / page_size), otherwise,
- * area allocations of (nr_pages * paze_size) won't be a
- * multiple of hpage_size, even if bytes is a multiple of
- * hpage_size.
- *
- * This means that nr_cpus must divide (N * (2 << (H-P))
- * where:
- * bytes = hpage_size * N
- * hpage_size = 2 << H
- * page_size = 2 << P
- *
- * And we want to chose nr_cpus to be the largest value
- * satisfying this constraint, not larger than the number
- * of online CPUs. Unfortunately, prime factorization of
- * N and nr_cpus may be arbitrary, so have to search for it.
- * Instead, just use the highest power of 2 dividing both
- * nr_cpus and (bytes / page_size).
- */
- int x = factor_of_2(nr_cpus);
- int y = factor_of_2(bytes / page_size);
-
- nr_cpus = x < y ? x : y;
- }
nr_pages_per_cpu = bytes / page_size / nr_cpus;
if (!nr_pages_per_cpu) {
_err("invalid MiB");
diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index bcd67bd4ec90..ecb8ba658736 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -332,6 +332,103 @@ static void uffd_pagemap_test(void)
uffd_test_pass();
}

+static void check_memory_contents(char *p)
+{
+ unsigned long i, j;
+ uint8_t expected_byte;
+
+ for (i = 0; i < nr_pages; ++i) {
+ expected_byte = ~((uint8_t)(i % ((uint8_t)-1)));
+ for (j = 0; j < page_size; j++) {
+ uint8_t v = *(uint8_t *)(p + (i * page_size) + j);
+ if (v != expected_byte)
+ err("unexpected page contents");
+ }
+ }
+}
+
+static void uffd_minor_test_common(bool test_collapse, bool test_wp)
+{
+ unsigned long p;
+ pthread_t uffd_mon;
+ char c;
+ struct uffd_stats stats = { 0 };
+
+ /*
+ * NOTE: MADV_COLLAPSE is not yet compatible with WP, so testing
+ * both do not make much sense.
+ */
+ assert(!(test_collapse && test_wp));
+
+ if (uffd_register(uffd, area_dst_alias, nr_pages * page_size,
+ /* NOTE! MADV_COLLAPSE may not work with uffd-wp */
+ false, test_wp, true))
+ err("register failure");
+
+ /*
+ * After registering with UFFD, populate the non-UFFD-registered side of
+ * the shared mapping. This should *not* trigger any UFFD minor faults.
+ */
+ for (p = 0; p < nr_pages; ++p)
+ memset(area_dst + (p * page_size), p % ((uint8_t)-1),
+ page_size);
+
+ stats.apply_wp = test_wp;
+ if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &stats))
+ err("uffd_poll_thread create");
+
+ /*
+ * Read each of the pages back using the UFFD-registered mapping. We
+ * expect that the first time we touch a page, it will result in a minor
+ * fault. uffd_poll_thread will resolve the fault by bit-flipping the
+ * page's contents, and then issuing a CONTINUE ioctl.
+ */
+ check_memory_contents(area_dst_alias);
+
+ if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+ err("pipe write");
+ if (pthread_join(uffd_mon, NULL))
+ err("join() failed");
+
+ if (test_collapse) {
+ if (madvise(area_dst_alias, nr_pages * page_size,
+ MADV_COLLAPSE)) {
+ /* It's fine to fail for this one... */
+ uffd_test_skip("MADV_COLLAPSE failed");
+ return;
+ }
+
+ uffd_test_ops->check_pmd_mapping(area_dst,
+ nr_pages * page_size /
+ read_pmd_pagesize());
+ /*
+ * This won't cause uffd-fault - it purely just makes sure there
+ * was no corruption.
+ */
+ check_memory_contents(area_dst_alias);
+ }
+
+ if (stats.missing_faults != 0 || stats.minor_faults != nr_pages)
+ uffd_test_fail("stats check error");
+ else
+ uffd_test_pass();
+}
+
+void uffd_minor_test(void)
+{
+ uffd_minor_test_common(false, false);
+}
+
+void uffd_minor_wp_test(void)
+{
+ uffd_minor_test_common(false, true);
+}
+
+void uffd_minor_collapse_test(void)
+{
+ uffd_minor_test_common(true, false);
+}
+
uffd_test_case_t uffd_tests[] = {
{
.name = "pagemap",
@@ -346,6 +443,29 @@ uffd_test_case_t uffd_tests[] = {
.uffd_feature_required =
UFFD_FEATURE_PAGEFAULT_FLAG_WP | UFFD_FEATURE_WP_UNPOPULATED,
},
+ {
+ .name = "minor",
+ .uffd_fn = uffd_minor_test,
+ .mem_targets = MEM_SHMEM | MEM_HUGETLB,
+ .uffd_feature_required =
+ UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM,
+ },
+ {
+ .name = "minor-wp",
+ .uffd_fn = uffd_minor_wp_test,
+ .mem_targets = MEM_SHMEM | MEM_HUGETLB,
+ .uffd_feature_required =
+ UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM |
+ UFFD_FEATURE_PAGEFAULT_FLAG_WP,
+ },
+ {
+ .name = "minor-collapse",
+ .uffd_fn = uffd_minor_collapse_test,
+ /* MADV_COLLAPSE only works with shmem */
+ .mem_targets = MEM_SHMEM,
+ /* We can't test MADV_COLLAPSE, so try our luck */
+ .uffd_feature_required = UFFD_FEATURE_MINOR_SHMEM,
+ },
};

int main(int argc, char *argv[])
--
2.39.1