From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout07.his.huawei.com (canpmsgout07.his.huawei.com [113.46.200.222]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5803C2F83A0 for ; Mon, 18 May 2026 15:05:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.222 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779116759; cv=none; b=sUGc9yq4LXLX/lzUzqK0reCzCBD4fJcKOIeHCpvFuCr6hYY/YHP4UKO73i6brKaKqFT8SXTyBUp4rF/v9vj3dKgiCVM+ZiQORVkZewxTErJzFTEIPnwkpoMDqlMZwKcKv7ptZ5NWOBCfeX53sm941ycxibEKcsBI2jp1Z6sua80= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779116759; c=relaxed/simple; bh=oNli51M9uH1iMZaQ7wfAUqGkngvHthCcQ0qJWOEtR90=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=QswwL1Ry3Z1ajXbFQogf7chpNC22eUea2T3lRMvwpghhbm1LxFGxgh7m7kZbNJqsWQ5z2Rr0FOnrlHxDGDRRs9rNp0LJBmSy5v+fi+LEkGQDpPiaUla9aY/0hLVrlwsERlDJdpuCAfCrToYEEeCtkKPNmz2Z0taJddB7wlI8EZ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=RX0ElzSc; arc=none smtp.client-ip=113.46.200.222 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="RX0ElzSc" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=y/0A0U2Miz8g6qlnLZ9M+S48R9RoXDn+PxaRIdMuKWw=; b=RX0ElzScjqNuMohNV0n+PGsOJK4o5h7/i9vlL2sQ9VyK6wXEJGcs3VrXf411MsQU1J6BdGm4V +QYDqtIEY2/9VB2OMtB0T6Y0dYKPAKtFDIYh53Bg6/h3V3XDWLJTBmKqy0Qb/YcoWpaXfsRJo8M kvipdlxr//vuYSo/1AAzWtA= Received: from mail.maildlp.com (unknown [172.19.162.92]) by canpmsgout07.his.huawei.com (SkyGuard) with ESMTPS id 4gK1Br0RpLzLlSx; Mon, 18 May 2026 22:58:12 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id E86F740565; Mon, 18 May 2026 23:05:51 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 18 May 2026 23:05:49 +0800 Message-ID: Date: Mon, 18 May 2026 23:05:47 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 0/8] arm64: add ARCH_HAS_COPY_MC support To: Ruidong Tian , , , , , , , , , , , , , , , , , , , , , , CC: , , , , References: <20260518084956.2538442-1-tianruidong@linux.alibaba.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: <20260518084956.2538442-1-tianruidong@linux.alibaba.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To dggpemf100008.china.huawei.com (7.185.36.138) On 5/18/2026 4:49 PM, Ruidong Tian wrote: > This series continues Tong Tiangen's work on arm64 ARCH_HAS_COPY_MC > support. We encounter the same problem, and from a forward-looking > perspective, large-memory ARM machines such as Grace and Vera will suffer > more from this class of issues, which motivates us to push this feature > upstream. > > Problem > ========= > With the increase of memory capacity and density, the probability of memory > error also increases. The increasing size and density of server RAM in data > centers and clouds have shown increased uncorrectable memory errors. > > Currently, more and more scenarios that can tolerate memory errors, such as > COW[1,2], KSM copy[3], coredump copy[4], khugepaged[5,6], uaccess copy[7], > etc. We have encountered more scenarios and have made more enhancements, eg, 658be46520ce mm: support poison recovery from copy_present_page() aa549f923f5e mm: support poison recovery from do_cow_fault() f00b295b9b61 fs: hugetlbfs: support poisoned recover from hugetlbfs_migrate_folio() 060913999d7a mm: migrate: support poisoned recover from migrate folio Hope that the architecture-related sections can receive relevant reviews and responses. Thanks. > Solution > ========= > > This patchset introduces a new processing framework on ARM64, which enables > ARM64 to support error recovery in the above scenarios, and more scenarios > can be expanded based on this in the future. > > In arm64, memory error handling in do_sea(), which is divided into two cases: > 1. If the user state consumed the memory errors, the solution is to kill > the user process and isolate the error page. > 2. If the kernel state consumed the memory errors, the solution is to > panic. > > For case 2, Undifferentiated panic may not be the optimal choice, as it can > be handled better. In some scenarios, we can avoid panic, such as uaccess, > if the uaccess fails due to memory error, only the user process will be > affected, returning an error to the caller and isolating the user page with > hardware memory errors is a better choice. > > [1] commit d302c2398ba2 ("mm, hwpoison: when copy-on-write hits poison, take page offline") > [2] commit 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage copy-on-write faults") > [3] commit 6b970599e807 ("mm: hwpoison: support recovery from ksm_might_need_to_copy()") > [4] commit 245f09226893 ("mm: hwpoison: coredump: support recovery from dump_user_range()") > [5] commit 98c76c9f1ef7 ("mm/khugepaged: recover from poisoned anonymous memory") > [6] commit 12904d953364 ("mm/khugepaged: recover from poisoned file-backed memory") > [7] commit 278b917f8cb9 ("x86/mce: Add _ASM_EXTABLE_CPY for copy user access") > > ------------------ > Test result: > > Tested on Kunpeng 920. > > 1. copy_page(), copy_mc_page() basic function test pass, and the disassembly > contents remains the same before and after refactor. > > 2. copy_to/from_user() access kernel NULL pointer raise translation fault > and dump error message then die(), test pass. > > 3. Test following scenarios: copy_from_user(), get_user(), COW. > > Before patched: trigger a hardware memory error then panic. > After patched: trigger a hardware memory error without panic. > > Testing step: > step1. start an user-process. > step2. poison(einj) the user-process's page. > step3: user-process access the poison page in kernel mode, then trigger SEA. > step4: the kernel will not panic, only the user process is killed, the poison > page is isolated. (before patched, the kernel will panic in do_sea()) > > The above tests can also be reproduced using ras-tools, which provides > einj-based injection and validation for uaccess and COW scenarios. > Example usage: > > einj_mem_uc futex # get_user > einj_mem_uc copyin # copy_to_user > einj_mem_uc copy-on-write # COW > > Link: https://git.kernel.org/pub/scm/linux/kernel/git/aegl/ras-tools.git > > ------------------ > > Benefits > ========= > According to Huawei's statistics from their storage products, memory errors > triggered in kernel-mode by COW and page cache read (uaccess) scenarios > account for more than 50%. With this patchset deployed, all kernel panics > caused by COW and page cache memory errors are eliminated. > Alibaba Cloud has also observed memory errors occurring in uaccess contexts. > > Since V13: > 1. Changed MC-safe functions to return an error rather than kill the user > process. When a user program invokes a syscall and the kernel encounters > a memory error during uaccess, killing the process is unexpected; the > syscall should return an error. > 2. Added FEAT_MOPS support for the copy_page_mc paths. > 3. Refactored copy_page() and memcpy() on top of the shared memcpy_template, > reducing duplicated assembly code. > > Since v12: > Thanks to the suggestions of Jonathan, Mark, and Mauro, the following modifications > are made: > 1. Rebase to latest kernel version. > 2. Patch1, add Jonathan's and Mauro's review-by. > 3. Patch2, modified do_apei_claim_sea() according to Mark's and Jonathan's suggestions, > and optimized the commit message according to Mark's suggestions(Added description of > the impact on regular copy_to_user()). > 4. Patch3, optimized the commit message according to Mauro's suggestions and add Jonathan's > review-by. > 5. Patch4, modified copy_mc_user_highpage() and Optimized the commit message according to > Jonathan's suggestions(no functional changes). > 6. Patch5, optimized the commit message according to Mauro's suggestions. > 7. Patch4/5, FEAT_MOPS is added to the code logic. Currently, the fixup is not performed > on the MOPS instruction. > 8. Remove patch6 in v12 according to Jonathan's suggestions. > > Since v11: > 1. Rebase to latest kernel version 6.9-rc1. > 2. Add patch 5, Since the problem described in "Since V10 Besides 3" has > been solved in a50026bdb867 ('iov_iter: get rid of 'copy_mc' flag'). > 3. Add the benefit of applying the patch set to our company to the description of patch0. > > Since V10: > Accroding Mark's suggestion: > 1. Merge V10's patch2 and patch3 to V11's patch2. > 2. Patch2(V11): use new fixup_type for ld* in copy_to_user(), fix fatal > issues (NULL kernel pointeraccess) been fixup incorrectly. > 3. Patch2(V11): refactoring the logic of do_sea(). > 4. Patch4(V11): Remove duplicate assembly logic and remove do_mte(). > > Besides: > 1. Patch2(V11): remove st* insn's fixup, st* generally not trigger memory error. > 2. Split a part of the logic of patch2(V11) to patch5(V11), for detail, > see patch5(V11)'s commit msg. > 3. Remove patch6(v10) “arm64: introduce copy_mc_to_kernel() implementation”. > During modification, some problems that cannot be solved in a short > period are found. The patch will be released after the problems are > solved. > 4. Add test result in this patch. > 5. Modify patchset title, do not use machine check and remove "-next". > > Since V9: > 1. Rebase to latest kernel version 6.8-rc2. > 2. Add patch 6/6 to support copy_mc_to_kernel(). > > Since V8: > 1. Rebase to latest kernel version and fix topo in some of the patches. > 2. According to the suggestion of Catalin, I attempted to modify the > return value of function copy_mc_[user]_highpage() to bytes not copied. > During the modification process, I found that it would be more > reasonable to return -EFAULT when copy error occurs (referring to the > newly added patch 4). > > For ARM64, the implementation of copy_mc_[user]_highpage() needs to > consider MTE. Considering the scenario where data copying is successful > but the MTE tag copying fails, it is also not reasonable to return > bytes not copied. > 3. Considering the recent addition of machine check safe support for > multiple scenarios, modify commit message for patch 5 (patch 4 for V8). > > Since V7: > Currently, there are patches supporting recover from poison > consumption for the cow scenario[1]. Therefore, Supporting cow > scenario under the arm64 architecture only needs to modify the relevant > code under the arch/. > [1]https://lore.kernel.org/lkml/20221031201029.102123-1-tony.luck@intel.com/ > > Since V6: > Resend patches that are not merged into the mainline in V6. > > Since V5: > 1. Add patch2/3 to add uaccess assembly helpers. > 2. Optimize the implementation logic of arm64_do_kernel_sea() in patch8. > 3. Remove kernel access fixup in patch9. > All suggestion are from Mark. > > Since V4: > 1. According Michael's suggestion, add patch5. > 2. According Mark's suggestiog, do some restructuring to arm64 > extable, then a new adaptation of machine check safe support is made based > on this. > 3. According Mark's suggestion, support machine check safe in do_mte() in > cow scene. > 4. In V4, two patches have been merged into -next, so V5 not send these > two patches. > > Since V3: > 1. According to Robin's suggestion, direct modify user_ldst and > user_ldp in asm-uaccess.h and modify mte.S. > 2. Add new macro USER_MC in asm-uaccess.h, used in copy_from_user.S > and copy_to_user.S. > 3. According to Robin's suggestion, using micro in copy_page_mc.S to > simplify code. > 4. According to KeFeng's suggestion, modify powerpc code in patch1. > 5. According to KeFeng's suggestion, modify mm/extable.c and some code > optimization. > > Since V2: > 1. According to Mark's suggestion, all uaccess can be recovered due to > memory error. > 2. Scenario pagecache reading is also supported as part of uaccess > (copy_to_user()) and duplication code problem is also solved. > Thanks for Robin's suggestion. > 3. According Mark's suggestion, update commit message of patch 2/5. > 4. According Borisllav's suggestion, update commit message of patch 1/5. > > Since V1: > 1.Consistent with PPC/x86, Using CONFIG_ARCH_HAS_COPY_MC instead of > ARM64_UCE_KERNEL_RECOVERY. > 2.Add two new scenes, cow and pagecache reading. > 3.Fix two small bug(the first two patch). > > V1 in here: > https://lore.kernel.org/lkml/20220323033705.3966643-1-tongtiangen@huawei.com/ > > Ruidong Tian (3): > ACPI: APEI: GHES: use exception context to gate SIGBUS on poison > consumption > lib/test: memcpy_kunit: add copy_page() and copy_mc_page() tests > lib/tests: memcpy_kunit: add memcpy_mc() and memcpy_mc_large() test > > Tong Tiangen (5): > uaccess: add generic fallback version of copy_mc_to_user() > arm64: add support for ARCH_HAS_COPY_MC > mm/hwpoison: return -EFAULT when copy fail in > copy_mc_[user]_highpage() > arm64: support copy_mc_[user]_highpage() > arm64: introduce copy_mc_to_kernel() implementation > > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/asm-extable.h | 22 ++- > arch/arm64/include/asm/asm-uaccess.h | 4 + > arch/arm64/include/asm/extable.h | 1 + > arch/arm64/include/asm/mte.h | 9 + > arch/arm64/include/asm/page.h | 10 ++ > arch/arm64/include/asm/string.h | 5 + > arch/arm64/include/asm/uaccess.h | 17 ++ > arch/arm64/kernel/acpi.c | 2 +- > arch/arm64/lib/Makefile | 2 + > arch/arm64/lib/copy_mc_page.S | 44 +++++ > arch/arm64/lib/copy_page.S | 62 +------ > arch/arm64/lib/copy_page_template.S | 71 ++++++++ > arch/arm64/lib/copy_to_user.S | 10 +- > arch/arm64/lib/memcpy.S | 253 ++------------------------- > arch/arm64/lib/memcpy_mc.S | 56 ++++++ > arch/arm64/lib/memcpy_template.S | 249 ++++++++++++++++++++++++++ > arch/arm64/lib/mte.S | 29 +++ > arch/arm64/mm/copypage.c | 75 ++++++++ > arch/arm64/mm/extable.c | 21 +++ > arch/arm64/mm/fault.c | 30 +++- > arch/powerpc/include/asm/uaccess.h | 1 + > arch/x86/include/asm/uaccess.h | 1 + > drivers/acpi/apei/ghes.c | 36 ++-- > include/acpi/ghes.h | 6 +- > include/linux/highmem.h | 16 +- > include/linux/uaccess.h | 8 + > lib/tests/memcpy_kunit.c | 178 ++++++++++++++++++- > mm/kasan/shadow.c | 12 ++ > mm/khugepaged.c | 4 +- > 30 files changed, 904 insertions(+), 331 deletions(-) > create mode 100644 arch/arm64/lib/copy_mc_page.S > create mode 100644 arch/arm64/lib/copy_page_template.S > create mode 100644 arch/arm64/lib/memcpy_mc.S > create mode 100644 arch/arm64/lib/memcpy_template.S >