On 3/18/26 05:18, 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]>
> ---
> 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?");
Wouldn't a check for 0 be
"!pmd_size" ? :)
But yes, this is unexpected. Maybe simply
"Could not detect PMD size"
> + return;
> + }
> + if (!detect_huge_zeropage()) {
> + uffd_test_skip("transparent huge zeropage disabled");
> + return;
> + }
> +
> + pmd_pages = pmd_size / gopts->page_size;
Might consider s/pmd_pages/nr_pages_per_pmd/
[...]
>
> +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);
A slightly nicer way to write it might be
const uint64_t expected = PAGE_IS_PRESENT | PAGE_IS_PFNZERO |
PAGE_IS_HUGE;
...
return (categories & expected) == huge_zero;
In general, lgtm, thanks!
--
Cheers,
David
