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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Cj5Tvm3GOgQ6hwsYhv5MYuKsZdtkk5Gxs/yjbSHzfcAJbDMNnsmY077R/ag8kn/wg 7wi6Zvd1tg/X9S2bA3EtIvFKuopik1Auxq+lW5Ku+MDefJSPklDMDjSXkW0lw2MCC6 +QzpnS9PTiDv/BBv5Fw2y6/jB1jiKY0wjM4snZoM= Date: Wed, 11 Nov 2026 18:19:34 +0000 From: Catalin Marinas To: "David Hildenbrand (Arm)" Cc: Yuanhe Shu , akpm@linux-foundation.org, "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 Subject: Re: [PATCH v3] mm/highmem: refuse to copy hwpoisoned folios in the !copy_mc fallbacks Message-ID: References: <20261110112641.1196786-1-xiangzao@linux.alibaba.com> <16cf88a0-6652-4276-95fb-12306e417701@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16cf88a0-6652-4276-95fb-12306e417701@kernel.org> X-Rspamd-Queue-Id: 7155A4000C X-Rspamd-Server: rspam12 X-Stat-Signature: s4nz8wp9b6h56p6nmtbt9yp6n1h1wknb X-Rspam-User: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794421181-769610 X-HE-Meta: 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 /c1mubZs 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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 Wed, Nov 11, 2026 at 10:36:40AM +0100, David Hildenbrand wrote: > 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). I think is_page_hwpoison() is compiled out unless CONFIG_MEMORY_FAILURE is enabled. Only arm64, parisc, powerpc and x86 enable it with the latter two having proper mc support. > > 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. Yeah, it's been around for some time. Lack of review cycles on our side as well. -- Catalin