From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12EBDC10DC3 for ; Mon, 4 Dec 2023 09:27:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232058AbjLDJ1t (ORCPT ); Mon, 4 Dec 2023 04:27:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229699AbjLDJ1q (ORCPT ); Mon, 4 Dec 2023 04:27:46 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7F3BBD8; Mon, 4 Dec 2023 01:27:52 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 702AA1650; Mon, 4 Dec 2023 01:28:38 -0800 (PST) Received: from [10.57.73.130] (unknown [10.57.73.130]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A46113F6C4; Mon, 4 Dec 2023 01:27:47 -0800 (PST) Message-ID: <744be4e0-48e0-4c77-825c-711386dd205f@arm.com> Date: Mon, 4 Dec 2023 09:27:45 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 5/5] selftests/mm: add UFFDIO_MOVE ioctl test Content-Language: en-GB To: Suren Baghdasaryan , David Hildenbrand Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com, lokeshgidra@google.com, peterx@redhat.com, hughd@google.com, mhocko@suse.com, axelrasmussen@google.com, rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.com, jannh@google.com, zhangpeng362@huawei.com, bgeffon@google.com, kaleshsingh@google.com, ngeoffray@google.com, jdduke@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-team@android.com References: <20231121171643.3719880-1-surenb@google.com> <20231121171643.3719880-6-surenb@google.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/2023 04:09, Suren Baghdasaryan wrote: > On Sat, Dec 2, 2023 at 2:11 AM David Hildenbrand 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 >>>>>> --- >>>>>> 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! > Thanks, > Suren. > >> >> -- >> Cheers, >> >> David / dhildenb >>