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Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0XEX4t7B_1794362088 cluster:ay36) by smtp.aliyun-inc.com; Wed, 11 Nov 2026 09:54:49 +0800 From: "Huang, Ying" To: Yuanhe Shu Cc: akpm@linux-foundation.org, david@kernel.org, "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 In-Reply-To: <20261110112641.1196786-1-xiangzao@linux.alibaba.com> (Yuanhe Shu's message of "Tue, 10 Nov 2026 19:26:41 +0800") References: <20261110112641.1196786-1-xiangzao@linux.alibaba.com> Date: Wed, 11 Nov 2026 09:54:48 +0800 Message-ID: <87jymkt9nb.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Stat-Signature: cbzu4i5jsfjt1c5c4gy5oid3hsz36okw X-Rspamd-Queue-Id: 560DA100004 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-19.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794362093-94425 X-HE-Meta: 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 SSb8Er2e PYEUADxHxNzzHan+t8dlswo4cnudJhw6iRjPHRJmZY8LS9CjB9qQGVVFUPV79PvtG+jD7gJb0PXE1RXjG+evQYxwfTVe1dEgW2xBmJBlloWVZuEFPmQFZypKVoSaHvdFk7O36saFM9pWVcqz0Vbrrr/15URjW1Fl2A/WCaRhrGDx8cy2MvJcdi0e01hDZ1jTZnhIHZ783ttxEU3BiMgsVvNG7CQAXsNMADE6nL400iNP/j+jFnJXhke3Yx9JsRRQ4mnEv2uZad4M8iuEHAcQ0igUaM7Jzhs//kcj0fwn4fsV5mQzHZYBILRbWg6AkTu1yzEWG8/0P0/tkZpW+sfaA87NyNzc7gfjofpwagcM82w3qAQR0GtzEJI31cxwQwRxAiLsE0A7ozvjfPeqdQUpCZtCbMAoJCciPI2uv3AVhUyDJ4UO+3/gSjVBeMwFSi9dKp6e4 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 Yuanhe Shu writes: > 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. IIUC, this is just RAS debug behavior, not real-world behavior. When poisoned memory is accessed, an MCE/SEA is triggered, and the kernel will panic without a proper copy_mc_* implementation. This patch reduces the probability of a panic, which I think is its main value. > 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. > > Suggested-by: "Huang, Ying" > Suggested-by: Kaitao Cheng > Assisted-by: LLM > Signed-off-by: Yuanhe Shu > Link: https://lore.kernel.org/r/877bjowf9i.fsf@DESKTOP-5N7EMDA/ > --- --- Best Regards, Huang, Ying