Re: [PATCH RESEND 1/1] selftests/mm: skip soft-dirty tests when CONFIG_MEM_SOFT_DIRTY is disabled

On 17.09.25 07:59, Lance Yang wrote:

From: Lance Yang lance.yang@linux.dev

The madv_populate and soft-dirty kselftests currently fail on systems where CONFIG_MEM_SOFT_DIRTY is disabled.

Introduce a new helper softdirty_is_supported() into vm_util.c/h to ensure tests are properly skipped when the feature is not enabled.

I'll note that tools/testing/selftests/mm/config contains

CONFIG_MEM_SOFT_DIRTY=y

But yes, the current arm64 handling is nasty, because some other archs (e.g., riscv) also don't support it yet.

LGTM, some nits below:

Suggested-by: David Hildenbrand david@redhat.com Signed-off-by: Lance Yang lance.yang@linux.dev

---

tools/testing/selftests/mm/madv_populate.c | 21 ++-------------- tools/testing/selftests/mm/soft-dirty.c | 5 +++- tools/testing/selftests/mm/vm_util.c | 28 ++++++++++++++++++++++ tools/testing/selftests/mm/vm_util.h | 1 + 4 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c index b6fabd5c27ed..43dac7783004 100644 --- a/tools/testing/selftests/mm/madv_populate.c +++ b/tools/testing/selftests/mm/madv_populate.c @@ -264,23 +264,6 @@ static void test_softdirty(void) munmap(addr, SIZE); } -static int system_has_softdirty(void) -{

• /*

• * There is no way to check if the kernel supports soft-dirty, other
  

• * than by writing to a page and seeing if the bit was set. But the
  

• * tests are intended to check that the bit gets set when it should, so
  

• * doing that check would turn a potentially legitimate fail into a
  

• * skip. Fortunately, we know for sure that arm64 does not support
  

• * soft-dirty. So for now, let's just use the arch as a corse guide.
  

• */
  

-#if defined(__aarch64__)

• return 0;

-#else

• return 1;

-#endif -}

• int main(int argc, char **argv) { int nr_tests = 16;

@@ -288,7 +271,7 @@ int main(int argc, char **argv) pagesize = getpagesize();

• if (system_has_softdirty())

• if (softdirty_is_supported()) nr_tests += 5;

ksft_print_header(); @@ -300,7 +283,7 @@ int main(int argc, char **argv) test_holes(); test_populate_read(); test_populate_write();

• if (system_has_softdirty())

• if (softdirty_is_supported()) test_softdirty();

err = ksft_get_fail_cnt(); diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c index 8a3f2b4b2186..98e42d2ac32a 100644 --- a/tools/testing/selftests/mm/soft-dirty.c +++ b/tools/testing/selftests/mm/soft-dirty.c @@ -200,8 +200,11 @@ int main(int argc, char **argv) int pagesize; ksft_print_header();

• ksft_set_plan(15);

• if (!softdirty_is_supported())

• ksft_exit_skip("soft-dirty is not support\n");
  

• ksft_set_plan(15); pagemap_fd = open(PAGEMAP_FILE_PATH, O_RDONLY); if (pagemap_fd < 0) ksft_exit_fail_msg("Failed to open %s\n", PAGEMAP_FILE_PATH);

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index 56e9bd541edd..3173335df775 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -449,6 +449,34 @@ bool check_vmflag_pfnmap(void *addr) return check_vmflag(addr, "pf"); } +bool softdirty_is_supported(void)

I'd just call it "softdirty_supported" similar to "pagemap_scan_supported()".

+{

• char *addr;
• int ret = 0;

bool supported = false;

• size_t pagesize;
• /* We know for sure that arm64 does not support soft-dirty. */

+#if defined(__aarch64__)

• return ret;

+#endif

Just drop this arm special case now.

• pagesize = getpagesize();

const size_t pagesize = getpagesize();

• /*

• * __mmap_complete() always sets VM_SOFTDIRTY for new VMAs, so we
  

• * just mmap a small region and check its VmFlags in /proc/self/smaps
  

• * for the "sd" flag.
  

• */
  

/* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */

• addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,

•     MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
  

• if (!addr)

• ksft_exit_fail_msg("mmap failed\n");
  

• if (check_vmflag(addr, "sd"))

• ret = 1;
  

supported = true;

• munmap(addr, pagesize);
• return ret;

+}