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    SubjectRe: [PATCH v4 5/5] selftests/mm: add UFFDIO_MOVE ioctl test
    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@google.com>
    > ---
    > 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?

    > +
    > +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.

    > + 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

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