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_supported() into vm_util.c/h to ensure tests are properly skipped when the feature is not enabled.

Acked-by: David Hildenbrand david@redhat.com Suggested-by: David Hildenbrand david@redhat.com Signed-off-by: Lance Yang lance.yang@linux.dev --- v2 -> v3: - Optimize softdirty_supported() by directly assigning check_vmflag() result (per David) - Pick AB from David - thanks! - https://lore.kernel.org/lkml/20250917122750.36608-1-lance.yang@linux.dev

v1 -> v2: - Rename softdirty_is_supported() to softdirty_supported() (per David) - Drop aarch64 specific handling (per David) - https://lore.kernel.org/lkml/20250917055913.49759-1-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 | 17 +++++++++++++++++ tools/testing/selftests/mm/vm_util.h | 1 + 4 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c index b6fabd5c27ed..d8d11bc67ddc 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_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_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..4ee4db3750c1 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_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..e33cda301dad 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -449,6 +449,23 @@ bool check_vmflag_pfnmap(void *addr) return check_vmflag(addr, "pf"); }

+bool softdirty_supported(void) +{ + char *addr; + bool supported = false; + const size_t pagesize = getpagesize(); + + /* 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"); + + supported = check_vmflag(addr, "sd"); + munmap(addr, pagesize); + return supported; +} + /* * Open an fd at /proc/$pid/maps and configure procmap_out ready for * PROCMAP_QUERY query. Returns 0 on success, or an error code otherwise. diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index 07c4acfd84b6..26c30fdc0241 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -104,6 +104,7 @@ bool find_vma_procmap(struct procmap_fd *procmap, void *address); int close_procmap(struct procmap_fd *procmap); int write_sysfs(const char *file_path, unsigned long val); int read_sysfs(const char *file_path, unsigned long *val); +bool softdirty_supported(void);

static inline int open_self_procmap(struct procmap_fd *procmap_out) {