On Wed, Mar 18, 2026 at 12:18:11PM +0800, Chris Down wrote: > The existing uffd-unit-tests move-pmd coverage exercises PMD-sized > UFFDIO_MOVE on anonymous THPs, but it does not force the huge zeropage > PMD path in move_pages_huge_pmd(). > > Add a dedicated anonymous UFFDIO_MOVE PMD test that exercises this > relatively comprehensively. > > Signed-off-by: Chris Down <[email protected]>
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> > --- > tools/testing/selftests/mm/uffd-unit-tests.c | 100 +++++++++++++++++++ > tools/testing/selftests/mm/vm_util.c | 12 +++ > tools/testing/selftests/mm/vm_util.h | 1 + > 3 files changed, 113 insertions(+) > > diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c > b/tools/testing/selftests/mm/uffd-unit-tests.c > index 6f5e404a446c..9cc4cbab9a23 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -1227,6 +1227,99 @@ static void uffd_move_pmd_test(uffd_global_test_opts_t > *gopts, uffd_test_args_t > uffd_move_pmd_handle_fault); > } > > +static void uffd_move_pmd_huge_zeropage_test(uffd_global_test_opts_t *gopts, > + uffd_test_args_t *targs) > +{ > + unsigned long pmd_size = read_pmd_pagesize(); > + unsigned long pmd_pages; > + unsigned long bytes = gopts->nr_pages * gopts->page_size; > + char *orig_area_src = gopts->area_src, *orig_area_dst = gopts->area_dst; > + char *aligned_src, *aligned_dst; > + unsigned long src_offs, dst_offs, max_offs; > + pthread_t uffd_mon; > + struct uffd_args args = { 0 }; > + char c = '\0'; > + int pagemap_fd; > + > + if (pmd_size <= gopts->page_size) { > + uffd_test_skip("huge page size is 0, feature missing?"); > + return; > + } > + if (!detect_huge_zeropage()) { > + uffd_test_skip("transparent huge zeropage disabled"); > + return; > + } > + > + pmd_pages = pmd_size / gopts->page_size; > + if (bytes < pmd_size) { > + uffd_test_skip("not enough pages for one PMD-sized move"); > + return; > + } > + > + aligned_src = ALIGN_UP(orig_area_src, pmd_size); > + aligned_dst = ALIGN_UP(orig_area_dst, pmd_size); > + src_offs = (aligned_src - orig_area_src) / gopts->page_size; > + dst_offs = (aligned_dst - orig_area_dst) / gopts->page_size; > + max_offs = src_offs > dst_offs ? src_offs : dst_offs; > + if (max_offs + pmd_pages > gopts->nr_pages) { > + uffd_test_skip("could not find aligned PMD-sized src/dst > window"); > + return; > + } > + > + if (madvise(orig_area_dst, bytes, MADV_HUGEPAGE)) > + err("madvise(MADV_HUGEPAGE) failure"); > + if (madvise(orig_area_src, bytes, MADV_DONTFORK)) > + err("madvise(MADV_DONTFORK) failure"); > + if (madvise(aligned_src, pmd_size, MADV_DONTNEED)) > + err("madvise(MADV_DONTNEED) failure"); > + > + /* Fault in a PMD-sized huge zeropage mapping in the source. */ > + force_read_pages(aligned_src, pmd_pages, gopts->page_size); > + > + pagemap_fd = pagemap_open(); > + if (!pagemap_is_huge_zero(pagemap_fd, aligned_src)) { > + close(pagemap_fd); > + uffd_test_skip("could not fault in the huge zeropage"); > + return; > + } > + gopts->area_src = aligned_src; > + gopts->area_dst = aligned_dst; > + > + if (uffd_register(gopts->uffd, gopts->area_dst, pmd_size, true, false, > false)) > + err("register failure"); > + > + args.gopts = gopts; > + args.handle_fault = uffd_move_pmd_handle_fault; > + if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) > + err("uffd_poll_thread create"); > + > + /* > + * One fault on dst should trigger a single PMD-sized UFFDIO_MOVE from > + * the huge zeropage PMD we populated in the source. > + */ > + force_read_pages(gopts->area_dst, pmd_pages, gopts->page_size); > + > + if (write(gopts->pipefd[1], &c, sizeof(c)) != sizeof(c)) > + err("pipe write"); > + if (pthread_join(uffd_mon, NULL)) > + err("join() failed"); > + > + if (args.missing_faults != 1 || args.minor_faults != 0) { > + uffd_test_fail("stats check error"); > + } else if (!pagemap_is_huge_zero(pagemap_fd, gopts->area_dst)) { > + uffd_test_fail("moved destination is not a huge zeropage PMD"); > + } else if (!check_huge_anon(gopts->area_dst, 0, pmd_size)) { > + /* vm_normal_page_pmd() must continue to treat the moved PMD as > special. */ > + uffd_test_fail("moved huge zeropage PMD counted as > AnonHugePages"); > + } else { > + uffd_test_pass(); > + } > + > + gopts->area_src = orig_area_src; > + gopts->area_dst = orig_area_dst; > + close(pagemap_fd); > +} > + > static void uffd_move_pmd_split_test(uffd_global_test_opts_t *gopts, > uffd_test_args_t *targs) > { > if (madvise(gopts->area_dst, gopts->nr_pages * gopts->page_size, > MADV_NOHUGEPAGE)) > @@ -1550,6 +1643,13 @@ uffd_test_case_t uffd_tests[] = { > .uffd_feature_required = UFFD_FEATURE_MOVE, > .test_case_ops = &uffd_move_test_pmd_case_ops, > }, > + { > + .name = "move-pmd-huge-zeropage", > + .uffd_fn = uffd_move_pmd_huge_zeropage_test, > + .mem_targets = MEM_ANON, > + .uffd_feature_required = UFFD_FEATURE_MOVE, > + .test_case_ops = &uffd_move_test_pmd_case_ops, > + }, > { > .name = "move-pmd-split", > .uffd_fn = uffd_move_pmd_split_test, > diff --git a/tools/testing/selftests/mm/vm_util.c > b/tools/testing/selftests/mm/vm_util.c > index a6d4ff7dfdc0..55cc4cc058a2 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -120,6 +120,18 @@ bool pagemap_is_populated(int fd, char *start) > PAGE_IS_PRESENT | PAGE_IS_SWAPPED); > } > > +bool pagemap_is_huge_zero(int fd, char *start) > +{ > + uint64_t categories; > + > + if (!pagemap_scan_supported(fd, start)) > + return false; > + > + categories = pagemap_scan_get_categories(fd, start); > + return (categories & (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | > PAGE_IS_HUGE)) == > + (PAGE_IS_PRESENT | PAGE_IS_PFNZERO | PAGE_IS_HUGE); > +} > + > unsigned long pagemap_get_pfn(int fd, char *start) > { > uint64_t entry = pagemap_get_entry(fd, start); > diff --git a/tools/testing/selftests/mm/vm_util.h > b/tools/testing/selftests/mm/vm_util.h > index e9c4e24769c1..e0b6ae1b12f5 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -85,6 +85,7 @@ uint64_t pagemap_get_entry(int fd, char *start); > bool pagemap_is_softdirty(int fd, char *start); > bool pagemap_is_swapped(int fd, char *start); > bool pagemap_is_populated(int fd, char *start); > +bool pagemap_is_huge_zero(int fd, char *start); > unsigned long pagemap_get_pfn(int fd, char *start); > void clear_softdirty(void); > bool check_for_pattern(FILE *fp, const char *pattern, char *buf, size_t len); > > base-commit: f0caa1d49cc07b30a7e2f104d3853ec6dc1c3cad > -- > 2.53.0 > -- Sincerely yours, Mike.
