On 05.12.23 05:46, Suren Baghdasaryan wrote:
On Mon, Dec 4, 2023 at 10:44 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
On Mon, Dec 4, 2023 at 10:27 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 04.12.23 17:35, Suren Baghdasaryan wrote:
On Mon, Dec 4, 2023 at 1:27 AM Ryan Roberts <ryan.roberts@xxxxxxx> wrote:
On 04/12/2023 04:09, Suren Baghdasaryan wrote:
On Sat, Dec 2, 2023 at 2:11 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 02.12.23 09:04, Ryan Roberts wrote:
On 01/12/2023 20:47, David Hildenbrand wrote:
On 01.12.23 10:29, Ryan Roberts wrote:
On 21/11/2023 17:16, 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 | 189 +++++++++++++++++++
3 files changed, 214 insertions(+)
diff --git a/tools/testing/selftests/mm/uffd-common.c
b/tools/testing/selftests/mm/uffd-common.c
index fb3bbc77fd00..b0ac0ec2356d 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -631,6 +631,30 @@ 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, unsigned long len)
+{
+ struct uffdio_move uffdio_move;
+
+ if (offset + len > nr_pages * page_size)
+ err("unexpected offset %lu and length %lu\n", offset, len);
+ uffdio_move.dst = (unsigned long) area_dst + offset;
+ uffdio_move.src = (unsigned long) area_src + offset;
+ uffdio_move.len = len;
+ 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);
Hi Suren,
FYI this error is triggering in mm-unstable (715b67adf4c8):
Testing move-pmd on anon... ERROR: UFFDIO_MOVE error: -16 (errno=16,
@uffd-common.c:648)
I'm running in a VM on Apple M2 (arm64). I haven't debugged any further, but
happy to go deeper if you can direct.
Does it trigger reliably? Which pagesize is that kernel using?
Yep, although very occasionally it fails with EAGAIN. 4K kernel; see other email
for full config.
I can spot that uffd_move_pmd_test()/uffd_move_pmd_handle_fault() uses
default_huge_page_size(), which reads the default hugetlb size.
My kernel command line is explicitly seting the default huge page size to 2M.
Okay, so that likely won't affect it.
I can only guess that it has to do with the alignment of the virtual
area we are testing with, and that we do seem to get more odd patterns
on arm64.
uffd_move_test_common() is a bit more elaborate, but if we aligned the
src+start area up, surely "step_count" cannot be left unmodified?
So assuming we get either an unaligned source or an unaligned dst from
mmap(), I am not convinced that we won't be moving areas that are not
necessarily fully backed by PMDs and maybe don't even fall into the VMA
of interest?
Not sure if that could trigger the THP splitting issue, though.
But I just quickly scanned that test setup, could be I am missing
something. It might make sense to just print the mmap'ed range and the
actual ranges we are trying to move. Maybe something "obvious" can be
observed.
I was able to reproduce the issue on an Android device and after
implementing David's suggestions to split the large folio and after
replacing default_huge_page_size() with read_pmd_pagesize(), the
move-pmd test started working for me. Ryan, could you please apply
attached patches (over mm-unstable) and try the test again?
Yep, all fixed with those patches!
Great! Thanks for testing and confirming. I'll post an updated
patchset later today and will ask Andrew to replace the current one
with it.
I'll also look into the reasons we need to split PMD on ARM64 in this
test. It's good that this happened and we were able to test the PMD
split path but I'm curious about the reason. It's possible my address
alignment calculations are somehow incorrect.
I only skimmed the diff briefly, but likely you also want to try
splitting in move_pages_pte(), if you encounter an already-pte-mapped THP.
Huh, good point. I might be able to move the folio splitting code into
pte-mapped case and do a retry after splitting. That should minimize
the additional code required. Will do and post a new set shortly.
Thanks!
Was planning to post an update today but need some more time. Will try
to send it tomorrow.
It would be great to have tests that cover these cases (having to
PTE-map a PMD-mapped THP, and stumbling over an already-PTE-mapped one).
--
Cheers,
David / dhildenb
