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b=FmhZfTAo1X3X3nFSSyzD8frnc24Y9FbVvba8A95uU6qmtT5PRbmLfFC7voQTFDjkX hCNouXYuHBhZH1e41jreW3yR5nJUJGcyVoBwH80C7Xvg7qsmjz3apEnn31zvJgzHtF ZiFQTydKCmtQlmlryMiEQJoMK59Xl+9kgai1vaBuWoMIqZdmf7sMsb41/JBCjmIzeR ff+hsJtKrJrVcqCXzHPa73frEXjQMVTENjEYDK+4jl1YcN9a0crZoi8aGQgo1Gh+DU qjV0eJZQENUMAFAFXbpEhIPJwSJ0IJ4l1VxOhgHx+X13U0kTeEvyK33AbKfmrxmWsH BiK7CCEW3H4UA== Message-ID: <16cf88a0-6652-4276-95fb-12306e417701@kernel.org> Date: Wed, 11 Nov 2026 10:36:40 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/highmem: refuse to copy hwpoisoned folios in the !copy_mc fallbacks To: Yuanhe Shu , akpm@linux-foundation.org Cc: "Huang, Ying" , Kaitao Cheng , "Garg, Shivank" , vbabka@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linmiaohe@huawei.com, nao.horiguchi@gmail.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, tujinjiang@huawei.com, mgorman@techsingularity.net, chengkaitao@kylinos.cn, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Catalin Marinas References: <20261110112641.1196786-1-xiangzao@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: BF64F140009 X-Rspamd-Server: rspam12 X-Stat-Signature: 8dxrguw8dyq6gy4w385k33us36f1dmjq X-Rspam-User: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794389812-776724 X-HE-Meta: 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 3MMSoXfV 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/10/26 12:26, Yuanhe Shu wrote: While the file touches highmem.h, this really isn't about highmem at all, right? This really affects any architecture except the ones that define copy_mc_to_kernel (x86+powerpc). Or am I missing something? Would be good to clarify that. > The !copy_mc fallbacks of copy_mc_user_highpage() and > copy_mc_highpage() return 0 after a plain copy. With PG_hwpoison > set while the data stays readable, there is no fault to recover > from: the copy completes, the destination folio carries no poison > marker, and the poison is consumed silently. > > Check the source page with is_page_hwpoison() in both fallbacks, > before the copy, and return PAGE_SIZE, the not-copied-bytes > convention of the real copy_mc paths, so the callers take their > existing error paths. On archs with copy_mc this code does not > compile. > > Measured on arm64, where the fallback code compiles: a > kernel-space microbenchmark measures 90.00 ns per copy before the > patch and 90.71 ns after, 0.8% of the copy itself. CCing Catalin. I'm surprised that arm64 cannot recover from a copy from a hwpoisoned page. -- Cheers, David