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t=1783687316; bh=Ul3sRLhwjrxQoJQnvumZ0PUhmDQ8XYv0aOjCqcjQNpM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fCVFfO9m4IzAP/wLQyhgQloMt80bQ5IwGpNIuTW9LwD9oZ/XvQAcTOdJGAM/c7dJE r9Yk5/nzIgBnh1LNVNhCLeoKT26eV18U8A9jSCt0j0pLm/rdT1CNRPYczRHWWE1cQO XLBswv9UmPxB0abMYjaKn2EyKBUvcG9DL04WZ9jEOqnQG1c+D5vdeBK4X9KBOnhOdE XUfM0AMy1Lh4Xh+hTvqWoh0ICLqxxg9a/jf5K+uizSCB/32YFTH45pnS7L+qZVduIc Y2P7dZTpm7THC3xWck3OwjF7SLg3wluXoKTppqOOvGN2RfOT8qJEa5vxM2ieFTU1fj Y8mvSwMOrzgQQ== Message-ID: Date: Fri, 10 Jul 2026 14:41:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] mm/huge_memory: skip device-private PMDs in madvise_free_huge_pmd To: Usama Arif , Andrew Morton , apopple@nvidia.com, balbirs@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, dev.jain@arm.com, gourry@gourry.net, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, matthew.brost@intel.com, npache@redhat.com, rakie.kim@sk.com, ryan.roberts@arm.com, vbabka@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, shakeel.butt@linux.dev, hannes@cmpxchg.org Cc: stable@vger.kernel.org References: <20260710105557.1987433-1-usama.arif@linux.dev> <20260710105557.1987433-4-usama.arif@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: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6EAD1A0004 X-Stat-Signature: qx3d3jwowo67j3esnsij1b3mcosmf357 X-HE-Tag: 1783687317-385392 X-HE-Meta: U2FsdGVkX188dUfeaM+mbryAQVx46PSw4rDwzJx1XOjxD0BErDCfwKJDZ2WksLjxtsqMZYf1w+flfdcN2skqCQHnJV4UwPzH11bWNX1enrl46KgvpCJx8oTL4AdYIyrmz4EWUkKqz9ajdrPOg45ANhwJrGu8g27h/k8Mdsd64Q6dJmn7mIIiO5+CDXVnQYY7nLWKuT37TzwnMsHlmn3OZdftuKLCIegnE1NpI0QcYvlSYzALUuttm/DEHnNYdKT9qiLvVJPX7fszWgwzkzf1FE6RrP+L4cMa7WYM0WTe8+YnXGDUdog4vYBcuvZkmQ/3QWK/I8s66chV9H9cFHymiFkwJE3g3TLzPg0jUuu481t54hi+YaFsseOjNNvIpRnn5/gMBVbb3PHmpCn9EArPjIW0ZusWmm3wBbeWHWzTtNLn5QFVW7+jCM1sfs3TpSD1oFDTw/wpOw8uYAX0N0Y0BtquLIvrkpZnl2NFSby1cxgdSX0HvHgjEHi80drkrUqSuP8AQMJg9cHkZ5fvSEYLbC2Z/lMB3sqpjPmHrnnpvQwXhadsakRmyCYc/R8zeWW1qMZAo0qCFtjtKIbADbPlfXm2M+KDFtBC1AoB+uZFwROI9N1g5p93BhhQVbHT2i9OMr+c55PEKOnHFlMVd1xib1PMeCC4xQ185qxZo6ii4Y6vh6Je086uuwFQ4yClpcoTgx9iDRb7ixYoc8OdqlBnDlSEjqGyz2xu0SN0D1YU5J775s796wyOlmWs0Us8EO8xhAePfbeU8lecRUxa0Z68SNC1QnzFc0t1cjoGW5zrQiCrOy+Xf2N4IDRe/Ut3ATziBodJG/oLaRZUp3RwC5y4Rr7IcIIa3NXDImaig5RCJNURuXHYID6DBcQ/R9QV99IAy3u1FRMUVZvnemk0PxVe1ce3i1siF0EkDMW2D9M5cPdujrk5FULLFFqm4wjPJo9bQ44z/sWapynPA7iFfEt kJ286F01 +3y/mj26xKOB99xhnqMRUJkTf5jULpDYs850LrF4cpNEAq+KXsVwRQOoQ8Qj6BZO16OtrrPlMn/j6NLV0Hlbam3Fbhwe3oXb8RE5ycikbuUcIehe7hpm9NW4DZ/O+ZGY74Tx5wV9G+bYgizq8yQGJF63P3HgmEFJkZF8C5GvqesmHitGtOtWs14LTn92613+QWHosws2BuTv9wSeN5RbD+NymMJDXCb9I98uZx4b9hmr7rnLna6Da+DbX4OZS4/X+qH173TwiQlwv0g0erKjLJkFHsZHLZuDEWQ5YoGtcNNWxsuXwVKD4fabnZy4TRbbidJAK9ycos2+t1UCJnxf2ScMOYp6al7rCX6eQeiAvoOJkIFw7F+jr3Npdnma6JOeWxE0PM4OiwJZKy0cSals4CLM7CXAby7YFWckmrXiC2gRkswmJRfgE+HHmZmFHxnzN//FYuOxNtnsV5dQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/10/26 12:55, Usama Arif wrote: > madvise_free_pte_range() checks pmd_trans_huge(*pmd) unlocked, then > madvise_free_huge_pmd() takes pmd_trans_huge_lock(). pmd_is_huge() > returns true for a device-private PMD, so orig_pmd can be device-private > and enter the !pmd_present() branch. > > Skip device-private PMDs in that non-present branch and continue to out > before calling pmd_folio(). Downgrade the check to VM_WARN_ON_ONCE() so > an unexpected PMD softleaf logs a warning rather than panicking. Drop > the thp_migration_supported() guard: it expands to > IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_SOFTLEAF), and both > pmd_is_migration_entry() and pmd_is_device_private_entry() already > return false when that config is not selected, so the guard suppresses > only the case where the warning would already be silent. > > Potential trigger: an HMM-based GPU driver races with madvise(MADV_FREE): > migrate_vma_pages() flips the PMD to a device-private entry between the > caller's pmd_trans_huge() check and the callee's pmd_trans_huge_lock(). > > Fixes: 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations") > Cc: > Reviewed-by: Joshua Hahn > Reviewed-by: Zi Yan > Reviewed-by: Balbir Singh > Signed-off-by: Usama Arif > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David