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bh=BFKdbCnvgEnPUCR+piUdwFlucy5SNy4ZmkD3FremwV0=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793761972; v=1; x=1794366772; b=MC8VPNm74Ok18sfdmxnpsI6xRh7R0Zk5W//KSoh4oQqgT/S/C7qdI564Yzn9q9U82YW5fQUa bHEVLCzq9Vqzf9FcDE7exA0+xlnDu1bTQ6V7pBzRG57qh+3OeK8awrDIx3MWDyYkXpPcFBKY+AD RqEEVje7E40Z3XH7oOIjjkYY= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 888f0105953f8a83; Wed, 04 Nov 2026 03:12:52 +0000 X-Mizu-Trace-ID: 888f0105953f8a83 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kees@kernel.org, peterz@infradead.org, jannh@google.com, pfalcato@suse.de, hughd@google.com, pasha.tatashin@soleen.com, pratyush@kernel.org, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, lance.yang@linux.dev, riel@surriel.com, harry@kernel.org, apopple@nvidia.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, jhubbard@nvidia.com, peterx@redhat.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, osalvador@suse.de, minchan@kernel.org, muchun.song@linux.dev, xu.xin@linux.dev, chengming.zhou@linux.dev, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, youngjun.park@lge.com, gourry@gourry.net, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, jgg@ziepe.ca, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, usama.anjum@arm.com Subject: Re: [PATCH v3 43/47] mm/huge_memory: split huge PUDs when adjusting VMA boundaries Date: Wed, 4 Nov 2026 11:12:45 +0800 Message-ID: <20261104031245.9524-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261031-fixes_core-v3-43-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-43-d6437171ecc3@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Sat, Oct 31, 2026 at 10:40:12AM +0100, David Hildenbrand (Arm) wrote: >PFN mappings such as VFIO PCI BAR mappings can use PUD leaves while >allowing VMA splits at page granularity. However, vma_adjust_trans_huge() >only handles PMDs. > >After faulting a writable PUD-sized VFIO BAR mapping, changing its first >page to read-only with mprotect() makes the PMD walk treat the PUD leaf >as a PMD table. Applying MADV_DONTFORK to the first PMD-sized chunk leaves >the PUD spanning two VMAs: the PMD-aligned boundary skips splitting. > >Walk the page tables once at each adjusted boundary and split a huge >PUD or PMD leaf as needed. Handle PUD leaves even when the boundary is >PMD-aligned. > >Fixes: f9e54c3a2f5b7 ("vfio/pci: implement huge_fault support") >Cc: stable@vger.kernel.org >Tested-by: Muhammad Usama Anjum >Reviewed-by: Kiryl Shutsemau (Meta) >Signed-off-by: David Hildenbrand (Arm) >--- Nice work! Reviewed-by: Lance Yang