Re: [PATCH v4 5/5] selftests/mm: add UFFDIO_MOVE ioctl test

[Suren Baghdasaryan]

On Mon, Oct 30, 2023 at 1:14 PM Peter Xu <peterx@xxxxxxxxxx> wrote:
>
> On Fri, Oct 27, 2023 at 05:38:15PM -0700, Suren Baghdasaryan wrote:
> > Add tests for new UFFDIO_MOVE ioctl which uses uffd to move source
> > into destination buffer while checking the contents of both after
> > the move. After the operation the content of the destination buffer
> > should match the original source buffer's content while the source
> > buffer should be zeroed. Separate tests are designed for PMD aligned and
> > unaligned cases because they utilize different code paths in the kernel.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > ---
> >  tools/testing/selftests/mm/uffd-common.c     |  24 ++++
> >  tools/testing/selftests/mm/uffd-common.h     |   1 +
> >  tools/testing/selftests/mm/uffd-unit-tests.c | 141 +++++++++++++++++++
> >  3 files changed, 166 insertions(+)
> >
> > diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
> > index 69e6653ad255..98957fd788d8 100644
> > --- a/tools/testing/selftests/mm/uffd-common.c
> > +++ b/tools/testing/selftests/mm/uffd-common.c
> > @@ -643,6 +643,30 @@ int copy_page(int ufd, unsigned long offset, bool wp)
> >       return __copy_page(ufd, offset, false, wp);
> >  }
> >
> > +int move_page(int ufd, unsigned long offset)
> > +{
> > +     struct uffdio_move uffdio_move;
> > +
> > +     if (offset >= nr_pages * page_size)
> > +             err("unexpected offset %lu\n", offset);
> > +     uffdio_move.dst = (unsigned long) area_dst + offset;
> > +     uffdio_move.src = (unsigned long) area_src + offset;
> > +     uffdio_move.len = page_size;
> > +     uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES;
> > +     uffdio_move.move = 0;
> > +     if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) {
> > +             /* real retval in uffdio_move.move */
> > +             if (uffdio_move.move != -EEXIST)
> > +                     err("UFFDIO_MOVE error: %"PRId64,
> > +                         (int64_t)uffdio_move.move);
> > +             wake_range(ufd, uffdio_move.dst, page_size);
> > +     } else if (uffdio_move.move != page_size) {
> > +             err("UFFDIO_MOVE error: %"PRId64, (int64_t)uffdio_move.move);
> > +     } else
> > +             return 1;
> > +     return 0;
> > +}
> > +
> >  int uffd_open_dev(unsigned int flags)
> >  {
> >       int fd, uffd;
> > diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h
> > index 19930fd6682b..c9526b2cb6b3 100644
> > --- a/tools/testing/selftests/mm/uffd-common.h
> > +++ b/tools/testing/selftests/mm/uffd-common.h
> > @@ -121,6 +121,7 @@ void wp_range(int ufd, __u64 start, __u64 len, bool wp);
> >  void uffd_handle_page_fault(struct uffd_msg *msg, struct uffd_args *args);
> >  int __copy_page(int ufd, unsigned long offset, bool retry, bool wp);
> >  int copy_page(int ufd, unsigned long offset, bool wp);
> > +int move_page(int ufd, unsigned long offset);
> >  void *uffd_poll_thread(void *arg);
> >
> >  int uffd_open_dev(unsigned int flags);
> > diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
> > index debc423bdbf4..89e9529ce941 100644
> > --- a/tools/testing/selftests/mm/uffd-unit-tests.c
> > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c
> > @@ -1064,6 +1064,133 @@ static void uffd_poison_test(uffd_test_args_t *targs)
> >       uffd_test_pass();
> >  }
> >
> > +static void uffd_move_handle_fault(
> > +     struct uffd_msg *msg, struct uffd_args *args)
> > +{
> > +     unsigned long offset;
> > +
> > +     if (msg->event != UFFD_EVENT_PAGEFAULT)
> > +             err("unexpected msg event %u", msg->event);
> > +
> > +     if (msg->arg.pagefault.flags &
> > +         (UFFD_PAGEFAULT_FLAG_WP | UFFD_PAGEFAULT_FLAG_MINOR | UFFD_PAGEFAULT_FLAG_WRITE))
> > +             err("unexpected fault type %llu", msg->arg.pagefault.flags);
> > +
> > +     offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
> > +     offset &= ~(page_size-1);
> > +
> > +     if (move_page(uffd, offset))
> > +             args->missing_faults++;
> > +}
> > +
> > +static void uffd_move_test(uffd_test_args_t *targs)
> > +{
> > +     unsigned long nr;
> > +     pthread_t uffd_mon;
> > +     char c;
> > +     unsigned long long count;
> > +     struct uffd_args args = { 0 };
> > +
> > +     /* Prevent source pages from being mapped more than once */
> > +     if (madvise(area_src, nr_pages * page_size, MADV_DONTFORK))
> > +             err("madvise(MADV_DONTFORK) failure");
> > +
> > +     if (uffd_register(uffd, area_dst, nr_pages * page_size,
> > +                       true, false, false))
> > +             err("register failure");
> > +
> > +     args.handle_fault = uffd_move_handle_fault;
> > +     if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args))
> > +             err("uffd_poll_thread create");
> > +
> > +     /*
> > +      * Read each of the pages back using the UFFD-registered mapping. We
> > +      * expect that the first time we touch a page, it will result in a missing
> > +      * fault. uffd_poll_thread will resolve the fault by moving source
> > +      * page to destination.
> > +      */
> > +     for (nr = 0; nr < nr_pages; nr++) {
> > +             /* Check area_src content */
> > +             count = *area_count(area_src, nr);
> > +             if (count != count_verify[nr])
> > +                     err("nr %lu source memory invalid %llu %llu\n",
> > +                         nr, count, count_verify[nr]);
> > +
> > +             /* Faulting into area_dst should move the page */
> > +             count = *area_count(area_dst, nr);
> > +             if (count != count_verify[nr])
> > +                     err("nr %lu memory corruption %llu %llu\n",
> > +                         nr, count, count_verify[nr]);
> > +
> > +             /* Re-check area_src content which should be empty */
> > +             count = *area_count(area_src, nr);
> > +             if (count != 0)
> > +                     err("nr %lu move failed %llu %llu\n",
> > +                         nr, count, count_verify[nr]);
> > +     }
> > +
> > +     if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
> > +             err("pipe write");
> > +     if (pthread_join(uffd_mon, NULL))
> > +             err("join() failed");
> > +
> > +     if (args.missing_faults != nr_pages || args.minor_faults != 0)
> > +             uffd_test_fail("stats check error");
> > +     else
> > +             uffd_test_pass();
> > +}
> > +
> > +static int prevent_hugepages(void)
> > +{
> > +     /* This should be done before source area is populated */
> > +     if (madvise(area_src, nr_pages * page_size, MADV_NOHUGEPAGE)) {
> > +             /* Ignore if CONFIG_TRANSPARENT_HUGEPAGE=n */
> > +             if (errno != EINVAL)
> > +                     return -errno;
> > +     }
> > +     return 0;
> > +}
> > +
> > +struct uffd_test_case_ops uffd_move_test_case_ops = {
> > +     .post_alloc = prevent_hugepages,
> > +};
> > +
> > +#define ALIGN_UP(x, align_to) \
> > +     (__typeof__(x))((((unsigned long)(x)) + ((align_to)-1)) & ~((align_to)-1))
> > +
> > +static char *orig_area_src, *orig_area_dst;
> > +static int pmd_align_areas(void)
> > +{
> > +     orig_area_src = area_src;
> > +     orig_area_dst = area_dst;
> > +     area_src = ALIGN_UP(area_src, page_size);
> > +     area_dst = ALIGN_UP(area_dst, page_size);
> > +     nr_pages--;
> > +
> > +     return 0;
> > +}
> > +
> > +static void pmd_restore_areas(void)
> > +{
> > +     area_src = orig_area_src;
> > +     area_dst = orig_area_dst;
> > +     nr_pages++;
> > +}
>
> Please stop using more global variables.. uffd tests are even less
> maintainable.
>
> Maybe you can consider add a flag for uffd_test_ctx_init()?  For allocating
> either small/thp/default?

I was considering that but was not sure which way would be more
preferable - using these new callbacks or adding new page size
requirements. I'll change to the latter.

>
>
> > +
> > +static int adjust_page_size(void)
> > +{
> > +     page_size = default_huge_page_size();
>
> This is hacky too, currently page_size is the real page_size backing the
> memory.
>
> To make thp test simple, maybe just add one more test to MOVE a large chunk
> to replace the thp test, which may contain a few thps?  It also doesn't
> need to be fault based.

Sorry, I didn't get your suggestion. Could you please clarify? Which
thp test are you referring to?

Thanks,
Suren.

>
> > +     nr_pages = UFFD_TEST_MEM_SIZE / page_size;
> > +
> > +     return 0;
> > +}
> > +
> > +struct uffd_test_case_ops uffd_move_pmd_test_case_ops = {
> > +     .pre_alloc = adjust_page_size,
> > +     .post_alloc = pmd_align_areas,
> > +     .pre_release = pmd_restore_areas,
> > +};
> > +
> >  /*
> >   * Test the returned uffdio_register.ioctls with different register modes.
> >   * Note that _UFFDIO_ZEROPAGE is tested separately in the zeropage test.
> > @@ -1141,6 +1268,20 @@ uffd_test_case_t uffd_tests[] = {
> >               .mem_targets = MEM_ALL,
> >               .uffd_feature_required = 0,
> >       },
> > +     {
> > +             .name = "move",
> > +             .uffd_fn = uffd_move_test,
> > +             .mem_targets = MEM_ANON,
> > +             .uffd_feature_required = UFFD_FEATURE_MOVE,
> > +             .test_case_ops = &uffd_move_test_case_ops,
> > +     },
> > +     {
> > +             .name = "move-pmd",
> > +             .uffd_fn = uffd_move_test,
> > +             .mem_targets = MEM_ANON,
> > +             .uffd_feature_required = UFFD_FEATURE_MOVE,
> > +             .test_case_ops = &uffd_move_pmd_test_case_ops,
> > +     },
> >       {
> >               .name = "wp-fork",
> >               .uffd_fn = uffd_wp_fork_test,
> > --
> > 2.42.0.820.g83a721a137-goog
> >
>
> --
> Peter Xu
>