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b=WXVQUnfRcR7QdAGNfG4lqnfdEi+SDlj6/QuImGNa7kvBBiZ5esx0GfFWj9JMuMO7P DTRH4vXPH4TLoQIAc1qpeEMQHmyrs2QY8I6pDSRLKRvd8gL1VyDAtPdhAXxqoYwTuc IQvgObBgcPtisgB/q9If8emoHa33ifGcpMd9ZjuLIFUGguYQpR7kRwjf/0DQJhZ1xn WCJ5JBWs6uHoF2AaZOjC5RkW2R8X08O0fgNHofo/HYX3qqJLLGWfY+PgpRnlss/uSx UFoh2CaNO8JnRAp2w9JMW3Hh1TemKaAg75UwTJcLK6bj/8LG8dBL7A/8zOFw9jN/vR ySa87WI8zNYgQ== Message-ID: <9da90d76-031f-4211-b9de-439cbf7bc63d@kernel.org> Date: Tue, 20 Oct 2026 15:58:30 +0200 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/compaction: skip folios containing hwpoisoned pages To: Kaitao Cheng , "Huang, Ying" , Yuanhe Shu Cc: akpm@linux-foundation.org, vbabka@kernel.org, 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 References: <20260928105805.1215770-1-xiangzao@linux.alibaba.com> <20260928105805.1215770-2-xiangzao@linux.alibaba.com> <99cbd960-439d-4672-aba9-6b49697db8b3@kernel.org> <20260929034123.2705745-1-xiangzao@linux.alibaba.com> <877bjowf9i.fsf@DESKTOP-5N7EMDA> <23d3756c-1a87-402d-80b4-c838dfc29f4d@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: AA4E640004 X-Stat-Signature: 3a7uteicsthnheyzuzgr96ugxtoco4tf X-Rspam-User: X-Spam-Status: No, score=-7.6 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: 1792504716-3774 X-HE-Meta: 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 cHnDGGz9 w3IdudtXLV1lYRH5g/B3rxamFKId8phnPcAZSV29Bz1rmqA8orp1GyNsNkxxrFg1Zyl5scLD/jT0CdJZMhPADTcSGUQeFtbdyygR624eLzbfX7RcrS5+OEFqRwXWtwzYldv4jzb4+DimyVD40Sn8G3GxK54325weVbHidVB5rwxbGjCLN466LCNJP3Y69VA82ltxnq56b7cNRsFhW8wNwm1pvsxA+chViyf8n5LDa7l2W2x+rkGsF4+P8xD2PxX7uyuBQZOtJ8NS318RV5PmmAyPD4aRqOEkfKZ9XGCteluZHGlGpOGjz+cyQxfEb1FGlDQgZbSol10em7bnkgErUZNQ3fe+5jHeXpU+Zf62k+rOLtz4= 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 10/20/26 15:31, Kaitao Cheng wrote: > > > 在 2026/10/20 21:07, David Hildenbrand (Arm) 写道: >> On 10/20/26 13:27, Kaitao Cheng wrote: >>> >>> >>> 在 2026/10/11 21:14, Huang, Ying 写道: >>> >>> On architectures with hardware error correction and exception recovery >>> support, accessing faulty memory automatically triggers an exception, >>> which itself guarantees atomicity. >>> >>> On architectures without such support, even if we implement this logic >>> in copy_mc_user_highpage() and copy_mc_highpage(), checking the hwpoison >>> flag and copying the data remain two separate operations. They cannot >>> be performed atomically, so there is still a race window between them, >>> however small. >> >> Yes. And you need proper architecture support to fix it? > > It does require architecture support, but that doesn't seem practical, haha. Well, but that's required when an arch wants to rule out all races. > >>> Moving the hwpoison check after the copy might address this issue. >>> Is there anything wrong with my understanding? >> >> Will architectures that are not prepared for copy_mc_user_highpage() not simply >> crash if they trigger an MCE during an access? >> > > Do we need to check both before and after the copy? This feels a bit > redundant, and I'm not sure whether such a small race window warrants > an additional check. > I don't see how checking after the copy makes any sense? :) You already crashed if there was a problem, why check? Or what am I missing? -- Cheers, David