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b=L3DTPkDZIUqx8Nk3kg9DUA6JR3HqOcCsSX4NbFsz4WFSgtNVQMdkoN5a41c62uDHv icaF8G3VgRIoGP6n4uD6rhGTP4oP3JqTLGKokoFQU50Q90ccE8OW7ZBi+a78i6djhh OV5Am7CETroE8xw1t6J4CsHdIuLYlbRsI1YALg2ZU9eL5UaEHal9eJxV5DRfSL/M1h B5nZuUCJFgaqeKICeh80D9+yBsHHLKezZHfHDc/raytvewe6gOcTukVLhi0/qQ5r6p LFQtXgKP47EPzEWteN1rHgtc6PM8M7bgUbfSp+oCHMzp6qPzikCzYqLMDhUe80knPC s4xvfwYyVo7Ew== Message-ID: <2e20d635-6326-48d1-af0b-776b15f47ce8@kernel.org> Date: Mon, 6 Jul 2026 10:46:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/6] mm/rmap: use huge_ptep_get() in try_to_migrate_one() To: Dev Jain , muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, apopple@nvidia.com, rcampbell@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, ak@linux.intel.com, nao.horiguchi@gmail.com, mel@csn.ul.ie, j-nomura@ce.jp.nec.com, pfalcato@suse.de, tglx@kernel.org, dave.hansen@intel.com, jpoimboe@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org References: <20260703114202.365553-1-dev.jain@arm.com> <20260703114202.365553-4-dev.jain@arm.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-Server: rspam06 X-Rspamd-Queue-Id: E367280005 X-Stat-Signature: eq9domg1r3uhtu9ir83tkxu94kp147ng X-Rspam-User: X-HE-Tag: 1783327613-137541 X-HE-Meta: U2FsdGVkX19RgoubQbnNNHYvj43cDJPUQoE3yw6w4GZDkEyEVG5pSt71v6bSJKiq5xKISPNUCkg3uLIFv+xzXdt/+t7cLdL9Z11Lo7tjv+4CymZ9OTAt2g2uU89MUyEZcdB8XR8PWXdNc4rM9wwVUP9u65slOunzpxJcvs31OtqUZqqawDC0o8VyFqx11j7iz7m4YHU8W+8DhoirpNkgrUIe+zELIIW5kdW1/R6vUc0D41Qyd5ZxZXIjMtRMB14uiFGvwo1LnWqTEjaNpr2tRRk2fxdfbPpRQTPkadYGwRP4GF9J34iSkNNUyvbSe57sJeVpptqExk0sf0BvvUkPWLv91Yb9pN/w3FDB8GTewDE2xO/7v8RobQgQYd2EUU6C7Cc0LPnjP5z2zWtT1gWAvC+Sp1C9/w7WyeFLUtcCgAUkkKUKxMaXDyvbUHZ8jnmNe7RjxhwMz+/naVv+TfX/Um5qFIwr4xTdgS5q9DY7L/1Wezq7AF8K817lTpeeqmRMuuTg4SbbrcL5eG2JyVLCpLnKE2oABxZy1eegFbi52W2GEHMiDhr7ztS1Rb5eA5gJf1lMLu88Xv/zCoxkFhqiHTUNR0p7Lo+mCTz4K/e28KVWoTPuN3N2szOKn3smzQTk7DOvPK1VgaVnA7/Tj305wMxirvIgJWYh6Dwg1Jy6vw7oU2tWFT9FQH7F1gGzUR4x/ObmfYo8dbW0a+1sgg9QJGA/b5YjJVD7YIu3XjmbrDurgeQComXtIZ3zArdh5TphDY5V4bidfK52K/gCNoXNbSp99SJsK29C78MLROQnQqBJB21wpT8ZaHUzG5Xl/aSpk2J3HzvWpXyfKtz8ofryRnPY7NHgznVSvbiLnXnnTLi3YzXhg0cDQGv3noBRx/CcEgh9K/3+57qaDuVs0EDG7ZjaL/bb++VAG2kMQBYrpAw3Y/P2x0czKFupkKX3ayhPnDEtyb0gcP0HpAjuOGi FaTsMgoi 2FOhANWcuTNe0IfR15KleSyzZ2RiyLVwrFRMPqLHTW0M0gZ/s4+KktOktWKpOgwenH2DKPuXKmkKDyQIxBsbSj3whVhKQ2cUXNw+T+upFFnZzUxIkgecSFQo/AeqGbNQ0X+ZTg1t6JXPHZ6hriaqkoDE9eflTP9HcgR6GDJ+o1gVOyElof02VfdDjCMPfItGM4WsQ5yM2rva+UEmBVXY69mFqKYSvMVZrbsVepkEz7zffRYAi/r6Y3o8fXx2C+eLTI/D2LivY01Kyo6d//aHzit0JesQeu1hRis68sM2B6s3SdLpKVft9FNWeZ18kudUIv7EobFs39iyXef3b3YqDcrlX+cpCxzrtGLlylhBO1B8uTW0AXJA+zrkqWyx4SQEtpHJAOEkThPrLzdNfBPeJRLS/Wo9ozgn3aBcoekG8Xd/M6iBskYYDWsKqMte3jxfu45nQzsDlNOP/Cvkcwl5SGJcp8Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/3/26 13:41, Dev Jain wrote: > try_to_migrate_one() is used by folio migration to replace a present > mapping with a migration entry. For hugetlb folios, page_vma_mapped_walk() > returns the pte pointer to the hugetlb folio in pvmw.pte, but the code > reads the huge pte entry with ptep_get(). > > On arches which provide their own huge_ptep_get() to dereference a huge > pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present() > etc to misbehave. > > It is not clear whether this has a trivially visible effect to userspace. > > Use huge_ptep_get() to dereference a huge pte pointer. > > Commit a98a2f0c8ce1 copied the bug from try_to_unmap_one into > try_to_migrate_one. > > Fixes: a98a2f0c8ce1 ("mm/rmap: split migration into its own function") > Cc: stable@vger.kernel.org > Acked-by: Muchun Song > Signed-off-by: Dev Jain > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David