Re: [PATCH v3 34/54] selftests/mm: hmm-tests: add setup of HugeTLB pages

Sarthak Sharma
2026-05-04T11:47:50Z

Hi Mike!

On 4/29/26 2:12 AM, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> hmm-tests skips HugeTLB tests if there are no free huge pages prepared by a
> wrapper script.
>
> Add setup of HugeTLB pages to the test and make sure that the original
> settings are restored on the test exit.
>
> Since kselftest_harness runs fixture setup and the tests in child
> processes, use HUGETLB_SETUP_DEFAULT_PAGES() that defines a constructor
> that runs in the main process and add verification that there are enough
> free huge pages to the tests that use them.
>
> Replace exit() calls with _exit() to avoid restoring HugeTLB settings in
> the middle of test and use SIGLILL to kill a child process in
> hmm_cow_in_device test to avoid interference with signal handlers in
> hugepage_restore_settings().
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 409b11cad4bc..70c7ae989c01 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -69,6 +69,9 @@ enum {
> #ifndef FOLL_LONGTERM
> #define FOLL_LONGTERM 0x100 /* mapping lifetime is indefinite */
> #endif
> +
> +HUGETLB_SETUP_DEFAULT_PAGES(1)
> +
> FIXTURE(hmm)
> {
> int fd;
> @@ -632,7 +635,7 @@ TEST_F(hmm, anon_write_child)
> }
>
> close(child_fd);
> - exit(0);
> + _exit(0);
> }
> }
> }
> @@ -712,7 +715,7 @@ TEST_F(hmm, anon_write_child_shared)
> ASSERT_EQ(ptr[i], -i);
>
> close(child_fd);
> - exit(0);
> + _exit(0);
> }
>
> /*
> @@ -784,8 +787,9 @@ TEST_F(hmm, anon_write_hugetlbfs)
> int *ptr;
> int ret;
>
> - if (!default_hsize)
> - SKIP(return, "Huge page size could not be determined");
> + if (!hugetlb_free_default_pages())
> + SKIP(return, "Not enough huge pages");
> + default_hsize = default_huge_page_size();

default_hsize has already been initialized at declaration above, so this
reassignment seems redundant. Shall we drop this?

>
> size = ALIGN(TWOMEG, default_hsize);
> npages = size >> self->page_shift;
> @@ -1564,9 +1568,9 @@ TEST_F(hmm, compound)
> unsigned long i;
>
> /* Skip test if we can't allocate a hugetlbfs page. */
> -
> - if (!default_hsize)
> - SKIP(return, "Huge page size could not be determined");
> + if (!hugetlb_free_default_pages())
> + SKIP(return, "Not enough huge pages");
> + default_hsize = default_huge_page_size();

Same thing here as well.

>
> size = ALIGN(TWOMEG, default_hsize);
> npages = size >> self->page_shift;
> @@ -2025,10 +2029,10 @@ TEST_F(hmm, hmm_cow_in_device)
> ptr[i] = i;
>
> /* Terminate child and wait */
> - EXPECT_EQ(0, kill(pid, SIGTERM));
> + EXPECT_EQ(0, kill(pid, SIGKILL));
> EXPECT_EQ(pid, waitpid(pid, &status, 0));
> EXPECT_NE(0, WIFSIGNALED(status));
> - EXPECT_EQ(SIGTERM, WTERMSIG(status));
> + EXPECT_EQ(SIGKILL, WTERMSIG(status));
>
> /* Take snapshot to CPU pagetables */
> ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);