We currently assume that the hugetlb page size is 2 MiB, which is why we mmap() a 2 MiB range.

Is the default hugetlb size is larger, mmap() will fail because the range is not suitable. If the default hugetlb size is smaller (e.g., s390x), mmap() will fail because we would need more than one hugetlb page, but just asserted that we have exactly one.

So let's simply use the default hugetlb page size instead of hard-coded 2 MiB, so the test isn't unconditionally skipped on architectures like s390x.

Before this patch on s390x: $ ./hugetlb_fault_after_madv 1..0 # SKIP Failed to allocated huge page

With this change on s390x: $ ./hugetlb_fault_after_madv

While at it, make "huge_ptr" static.

Reported-by: Mario Casquero mcasquer@redhat.com Signed-off-by: David Hildenbrand david@redhat.com --- .../selftests/mm/hugetlb_fault_after_madv.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c index 73b81c632366..ff3ba675278d 100644 --- a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c @@ -9,10 +9,10 @@ #include "vm_util.h" #include "../kselftest.h"

-#define MMAP_SIZE (1 << 21) #define INLOOP_ITER 100

-char *huge_ptr; +static char *huge_ptr; +static size_t huge_page_size;

/* Touch the memory while it is being madvised() */ void *touch(void *unused) @@ -30,7 +30,7 @@ void *madv(void *unused) usleep(rand() % 10);

for (int i = 0; i < INLOOP_ITER; i++) - madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); + madvise(huge_ptr, huge_page_size, MADV_DONTNEED);

return NULL; } @@ -47,6 +47,10 @@ int main(void)

srand(getpid());

+ huge_page_size = default_huge_page_size(); + if (!huge_page_size) + ksft_exit_skip("Could not detect default hugetlb page size."); + free_hugepages = get_free_hugepages(); if (free_hugepages != 1) { ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", @@ -54,7 +58,7 @@ int main(void) }

while (max--) { - huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, + huge_ptr = mmap(NULL, huge_page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);

@@ -66,7 +70,7 @@ int main(void)

pthread_join(thread1, NULL); pthread_join(thread2, NULL); - munmap(huge_ptr, MMAP_SIZE); + munmap(huge_ptr, huge_page_size); }

return KSFT_PASS;

Let's improve the test output. For example, print the proper test result. Install a SIGBUS handler to catch any SIGBUS instead of crashing the test on failure.

With unsuitable hugetlb page count: $ ./hugetlb_fault_after_madv TAP version 13 1..1 # [INFO] detected default hugetlb page size: 2048 KiB ok 2 # SKIP This test needs one and only one page to execute. Got 0 # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0

On a failure: $ ./hugetlb_fault_after_madv TAP version 13 1..1 not ok 1 SIGBUS behavior Bail out! 1 out of 1 tests failed

On success: $ ./hugetlb_fault_after_madv TAP version 13 1..1 # [INFO] detected default hugetlb page size: 2048 KiB ok 1 SIGBUS behavior # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: David Hildenbrand david@redhat.com --- .../selftests/mm/hugetlb_fault_after_madv.c | 34 ++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c index ff3ba675278d..e2640529dbb2 100644 --- a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c @@ -5,6 +5,8 @@ #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> +#include <setjmp.h> +#include <signal.h>

#include "vm_util.h" #include "../kselftest.h" @@ -14,11 +16,25 @@ static char *huge_ptr; static size_t huge_page_size;

+static sigjmp_buf sigbuf; +static bool sigbus_triggered; + +static void signal_handler(int signal) +{ + if (signal == SIGBUS) { + sigbus_triggered = true; + siglongjmp(sigbuf, 1); + } +} + /* Touch the memory while it is being madvised() */ void *touch(void *unused) { char *ptr = (char *)huge_ptr;

+ if (sigsetjmp(sigbuf, 1)) + return NULL; + for (int i = 0; i < INLOOP_ITER; i++) ptr[0] = '.';

@@ -44,13 +60,23 @@ int main(void) * interactions */ int max = 10000; + int err; + + ksft_print_header(); + ksft_set_plan(1);

srand(getpid());

+ if (signal(SIGBUS, signal_handler) == SIG_ERR) + ksft_exit_skip("Could not register signal handler."); + huge_page_size = default_huge_page_size(); if (!huge_page_size) ksft_exit_skip("Could not detect default hugetlb page size.");

+ ksft_print_msg("[INFO] detected default hugetlb page size: %zu KiB\n", + huge_page_size / 1024); + free_hugepages = get_free_hugepages(); if (free_hugepages != 1) { ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", @@ -73,5 +99,11 @@ int main(void) munmap(huge_ptr, huge_page_size); }

- return KSFT_PASS; + ksft_test_result(!sigbus_triggered, "SIGBUS behavior\n"); + + err = ksft_get_fail_cnt(); + if (err) + ksft_exit_fail_msg("%d out of %d tests failed\n", + err, ksft_test_num()); + ksft_exit_pass(); }