Re: [PATCH v3 3/3] selftests/mm: add UFFDIO_MOVE ioctl test

From: Peter Xu
Date: Thu Oct 19 2023 - 15:34:15 EST

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In reply to: Axel Rasmussen: "Re: [PATCH v3 3/3] selftests/mm: add UFFDIO_MOVE ioctl test"
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On Thu, Oct 19, 2023 at 10:29:27AM -0700, Axel Rasmussen wrote:
> On Thu, Oct 19, 2023 at 8:43 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> >
> > On Thu, Oct 12, 2023 at 3:29 PM Peter Xu <peterx@xxxxxxxxxx> wrote:
> > >
> > > On Sun, Oct 08, 2023 at 11:42:28PM -0700, Suren Baghdasaryan wrote:
> > > > Add a test for new UFFDIO_MOVE ioctl which uses uffd to move source
> > > > into destination buffer while checking the contents of both after
> > > > remapping. After the operation the content of the destination buffer
> > > > should match the original source buffer's content while the source
> > > > buffer should be zeroed.
> > > >
> > > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > > > ---
> > > > tools/testing/selftests/mm/uffd-common.c | 41 ++++++++++++-
> > > > tools/testing/selftests/mm/uffd-common.h | 1 +
> > > > tools/testing/selftests/mm/uffd-unit-tests.c | 62 ++++++++++++++++++++
> > > > 3 files changed, 102 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
> > > > index 02b89860e193..ecc1244f1c2b 100644
> > > > --- a/tools/testing/selftests/mm/uffd-common.c
> > > > +++ b/tools/testing/selftests/mm/uffd-common.c
> > > > @@ -52,6 +52,13 @@ static int anon_allocate_area(void **alloc_area, bool is_src)
> > > > *alloc_area = NULL;
> > > > return -errno;
> > > > }
> > > > +
> > > > + /* Prevent source pages from collapsing into THPs */
> > > > + if (madvise(*alloc_area, nr_pages * page_size, MADV_NOHUGEPAGE)) {
> > > > + *alloc_area = NULL;
> > > > + return -errno;
> > > > + }
> > >
> > > Can we move this to test specific code?
> >
> > Ack. I think that's doable.
> >
> > >
> > > > +
> > > > return 0;
> > > > }
> > > >
> > > > @@ -484,8 +491,14 @@ void uffd_handle_page_fault(struct uffd_msg *msg, struct uffd_args *args)
> > > > offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
> > > > offset &= ~(page_size-1);
> > > >
> > > > - if (copy_page(uffd, offset, args->apply_wp))
> > > > - args->missing_faults++;
> > > > + /* UFFD_MOVE is supported for anon non-shared mappings. */
> > > > + if (uffd_test_ops == &anon_uffd_test_ops && !map_shared) {
> > >
> > > IIUC this means move_page() will start to run on many other tests... as
> > > long as anonymous & private. Probably not wanted, because not all tests
> > > may need this MOVE test, and it also means UFFDIO_COPY is never tested on
> > > anonymous..
> > >
> > > You can overwrite uffd_args.handle_fault(). Axel just added a hook which
> > > seems also usable here. See 99aa77215ad02.
> >
> > Yes, I was thinking about adding a completely new set of tests for
> > UFFDIO_MOVE but was not sure. With your confirmation I'll follow that
> > path so that UFFDIO_COPY tests stay the same.

Sounds good.

If you want you can also torture MOVE a bit with uffd-stress.c to do
bouncing test all with MOVE, may need a new option and some more code
changes, though.

> >
> > >
> > > > + if (move_page(uffd, offset))
> > > > + args->missing_faults++;
> > > > + } else {
> > > > + if (copy_page(uffd, offset, args->apply_wp))
> > > > + args->missing_faults++;
> > > > + }
> > > > }
> > > > }
> > > >
> > > > @@ -620,6 +633,30 @@ 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 7c4fa964c3b0..f4d79e169a3d 100644
> > > > --- a/tools/testing/selftests/mm/uffd-common.h
> > > > +++ b/tools/testing/selftests/mm/uffd-common.h
> > > > @@ -111,6 +111,7 @@ 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 2709a34a39c5..f0ded3b34367 100644
> > > > --- a/tools/testing/selftests/mm/uffd-unit-tests.c
> > > > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c
> > > > @@ -824,6 +824,10 @@ static void uffd_events_test_common(bool wp)
> > > > char c;
> > > > 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) failed");
> > >
> > > Modifying events test is weird.. I assume you don't need this anymore after
> > > you switch to the handle_fault() hook.
> >
> > I think so but let me try first and I'll get back on that.
> >
> > >
> > > > +
> > > > fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
> > > > if (uffd_register(uffd, area_dst, nr_pages * page_size,
> > > > true, wp, false))
> > > > @@ -1062,6 +1066,58 @@ static void uffd_poison_test(uffd_test_args_t *targs)
> > > > uffd_test_pass();
> > > > }
> > > >
> > > > +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 };
> > > > +
> > > > + if (uffd_register(uffd, area_dst, nr_pages * page_size,
> > > > + true, false, false))
> > > > + err("register failure");
> > > > +
> > > > + 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 remapping 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 remap 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]);
> > >
> > > All of above should see zeros, right? Because I don't think anyone boosted
> > > the counter at all..
> > >
> > > Maybe set some non-zero values to it? Then the re-check can make more
> > > sense.
> >
> > I thought uffd_test_ctx_init() is initializing area_count(area_src,
> > nr), so the source pages should contain non-zero data before the move.
> > Am I missing something?
>
> You're correct, uffd_test_ctx_init() fills in some data in area_src.

Indeed.

>
> >
> > >
> > > If you want, I think we can also make uffd-stress.c test to cover MOVE too,
> > > basically replacing all UFFDIO_COPY when e.g. user specified from cmdline.
> > > Optional, and may need some touch ups here and there, though.
> >
> > That's a good idea. I'll add that in the next version.
> > Thanks,
> > Suren.
> >
> > >
> > > Thanks,
> > >
> > > > + }
> > > > +
> > > > + 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();
> > > > +}
> > > > +
> > > > /*
> > > > * Test the returned uffdio_register.ioctls with different register modes.
> > > > * Note that _UFFDIO_ZEROPAGE is tested separately in the zeropage test.
> > > > @@ -1139,6 +1195,12 @@ 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,
> > > > + },
> > > > {
> > > > .name = "wp-fork",
> > > > .uffd_fn = uffd_wp_fork_test,
> > > > --
> > > > 2.42.0.609.gbb76f46606-goog
> > > >
> > >
> > > --
> > > Peter Xu
> > >
> > > --
> > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@xxxxxxxxxxx.
> > >
>

--
Peter Xu

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Previous message: Martin KaFai Lau: "Re: [PATCH v7 02/11] bpf: Add sockptr support for setsockopt"
In reply to: Axel Rasmussen: "Re: [PATCH v3 3/3] selftests/mm: add UFFDIO_MOVE ioctl test"
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