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t=1783687324; bh=Ul3sRLhwjrxQoJQnvumZ0PUhmDQ8XYv0aOjCqcjQNpM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iTPZDjsZPGmzN5+vwYYtBkEavSQKPLJaVniKtsesqVlHMN/bvuWdgrvmGVDmu/eiH 0mFYun3HE1zMV87WcauZgUZ/3c/TWL/epVu6UgyTKU6mIKmXn7kfrvo30JHrExzZ93 X0yO+L4gkL0ZeJ8rrZMydc/xZP7/aqXzrgI1pMOUdKVJ/q7uKoXfnCOKh1wwLD1krj czDViz5NaH24tW3yoRoR5Pqt+4HEm3xe8wt1/sHbty9xwk2Utg+lnbWql4zc8/5uzf P+K3LuDd6voF3tR0LCtb6Ov5bHRppYcfIbXZUIAiSUDzyZN8xMRW6a1G2fNe2yGFp4 oFryCi5+eL3wg== Message-ID: <82607f71-8fdd-4a97-8350-810bb6c65f75@kernel.org> Date: Fri, 10 Jul 2026 14:41:57 +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: 429CF40002 X-Stat-Signature: qx3d3jwowo67j3esnsij1b3mcosmf357 X-HE-Tag: 1783687325-449522 X-HE-Meta: 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 GgYNTsEz Cs3tOZdseMgBCA4eYBcJ1CJHPq6u4hgyI5EeRTq4TUoIrFW+8v563vvfv/AifQ6PIFzPWOzmdoreMuHYDtW5EWilr0QhEYasZG7C1eqyvKDqlq9U6B1Sy8/ruVub9ucjEtTXVo8PJ08P+G4kOqz+YcR7Q1Nc84UGEO91E/KpRKMNoNYHHu0LrX/5CdTjM1cCZ2a65DTObQPcmNPCJedLhSyDuCy0NzTEYRgUD6skmkviGi5tdqH9h7CjibBSGX/Pdx6+ln975CsRZORRxeIpcv2xY/t/KeEleRNYlNOtEYFoImjWYBRMdUBwcsPmAWfYyn87Y8anRGbTtbEkWn6qeSSekan7e16YLm0UvxyZ9d0sPyj2w56jdgZD/x6+Poudvhrw6GktVTyOqj5YdePStboZYZ01JoYA6bdYeGgtx49fC82cxlf84hkGpwMBFlIeuM+ZbyE02WXiowOc= 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