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Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0X6dH8g._1783422486 cluster:ay36) by smtp.aliyun-inc.com; Tue, 07 Jul 2026 19:08:07 +0800 From: "Huang, Ying" To: "David Hildenbrand (Arm)" , Kaitao Cheng Cc: Andrew Morton , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Alistair Popple , Naoya Horiguchi , Andi Kleen , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kaitao Cheng Subject: Re: [PATCH v2] mm/migrate: Avoid copying hwpoisoned folios during migration In-Reply-To: (David Hildenbrand's message of "Tue, 7 Jul 2026 12:08:26 +0200") References: <20260707090136.52904-1-kaitao.cheng@linux.dev> Date: Tue, 07 Jul 2026 19:08:06 +0800 Message-ID: <87o6gjnjl5.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6DDE040006 X-Stat-Signature: oqb4mhkyfzswkcho5kntnez6rjugouzk X-HE-Tag: 1783422492-986019 X-HE-Meta: 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 XYmi0fXM zsfV9RbEvwIQFpH9igWVsQ6AqNzjjF6s1uKXZsLvu+6pX2cum8LVW0YbCEmSHUQJLUSHHCDA4PQVnXLEtGqFGMVhddBfNlrua4bNQyy4sCy3zOzwav65GtBClO4pMP4fTOOw1z4zu31IMMPSpsg2esCJaMNfvePwUYUHeAyffmAmEuxtAGZBLC8JH4S5TiTNpgIuyDTjg+0msnQEfPycwjHLweg9JB2+hJ9VJgM6mINMsA01VX7hTcmMh3S1JCoxmvgbvrvSUeCCbDv59V76k1IvcO5sSdAjSTHU7yktR1wRxkmMCRz7V4fNyg7UJDJen1ObTpANhfyWHaIys7vj9CyVXuDL4HI5NMqlOnxgOLS6RkUavS22g0ffpPw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: "David Hildenbrand (Arm)" writes: > On 7/7/26 11:01, Kaitao Cheng wrote: >> From: Kaitao Cheng >> >> The generic folio migration path can copy the source folio after it has >> been unmapped. For normal and THP folios this goes through >> move_to_new_folio(), then the filesystem or anonymous migration callback, >> and commonly reaches folio_mc_copy(). >> >> folio_mc_copy() uses copy_mc_highpage(), but architectures without >> copy_mc_to_kernel support fall back to copy_highpage(). If the source >> folio already contains a hwpoisoned page, a normal copy can consume the >> poisoned memory and trigger a synchronous machine check. > > Well, but the code can still race with memory_failure() IIUC, so it's not really > safe either? Yes. So the better way to fix this is to implement copy_mc_to_kernel() for the target architectures, or to implement the trick in the fallback? --- Best Regards, Huang, Ying