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b=FWr7oYXOt5Tp+K6Ek8q6APpXSMD+p/aNq4SvRIWBniP6sobBE8u2g/45GuabtZ7Lh 5E6jKvT6FbQ902LJvZk8l9k4niP2mOqpY3EAy0PXbjEdEmkzyqGxqmXJfvqHOtrnHp 7W8TPuCgfYN9bK/6++23sY3tVDsVYxqEXnEpRnKA= Date: Sun, 5 Jul 2026 00:35:59 -0700 From: Andrew Morton To: Dev Jain Cc: muchun.song@linux.dev, osalvador@suse.de, ljs@kernel.org, david@kernel.org, liam@infradead.org, 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 Subject: Re: [PATCH v3 1/6] arm64: make huge_ptep_get handled unaligned addresses Message-Id: <20260705003559.8b124d2b94b685cc2e4e77ae@linux-foundation.org> In-Reply-To: <20260703114202.365553-2-dev.jain@arm.com> References: <20260703114202.365553-1-dev.jain@arm.com> <20260703114202.365553-2-dev.jain@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8F1C340007 X-Stat-Signature: 3cifjobuf5zgatnc5jobx786pr8tbh14 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1783236962-984912 X-HE-Meta: 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 bGqg0erB LNtkQkp2l9gzps150/UUdSn08uf6T6kuZwtybrxgGE44dq9qg+GlTQKeSfeV7KKsBliTA7DQT/YlfSevt/AQPMFvNYVZFFgDVvTkdjZt/useosAD+5vrAmQ5RCIhpnTuG9qhFwAsChHete1Qgn2LWsH/3KtfxHmAhUMGrL2+5xALvxxdHxteprc1VxY9YSobNG15rqWK49xZZ1KIBbQeOIrLeyycFAdofIJjvwJWBudnLV4WmX2J8l7ckBPMSYUvQK/zwOYyh9Rb4f4uOCTKzVza0hbZ6qaFDiXuAbVyznnBi0qc/GI+43MtxeZEHUNNytMWFIwutDkpaK2TA/1ydbBH69aw0QJfpUvT5Y0PnGfNvkrt256iRqTMXRpFGhDvR1hQXyBj40uxwIDfHyVZ8JwEaYcAKHI9lMl3JbJROX49R+w77wrrDrccLmmfu3BzM9zU9z3a/b4RSi5g= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 3 Jul 2026 11:41:54 +0000 Dev Jain wrote: > huge_ptep_get() can be handed a virtual address pointing to the middle of > a contpmd/contpte mapped hugetlb folio (examples of callers are > pagemap_hugetlb_range, page_mapped_in_vma). > > The arm64 helper rewalks the pgtables in find_num_contig to answer whether > the huge pte we have maps a contpmd or a contpte hugetlb folio, and > returns CONT_PMDS or CONT_PTES, so that it can collect a/d bits over the > contiguous ptes. We can falsely return CONT_PTES instead of CONT_PMDS > if the addr is not aligned. > > Fix this by aligning the pmdp pointer down to a contpmd base before > checking equality with the passed huge pte pointer, to correctly answer > whether the huge pte is the base of a contpmd block. > > Fixes: 29cb80519689 ("arm64: hugetlb: Cleanup huge_pte size discovery mechanisms") > Cc: stable@vger.kernel.org Please describe the userspace-visible effects of bugs when fixing them. Particularly when cc:stable is proposed. Thanks.