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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-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: 9stbys1gndnhag1w3wt63eog5u9m755t X-Rspam-User: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: AE566180002 X-HE-Tag: 1793761974-140659 X-HE-Meta: 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 DFYjVCFd E3J4xrRrGVKjHt2JZhDjIm4lsKCP8slN/FckVvITEVK0Agxa/4CMDUh5FdiTEW8hETskXO8U5xcG5vlwYuaXsvS8ExiSUdw3CVRpoc0v2Pi5s/3CN9KTL/7kgNysHgIOuakOfuaYK27y/AsHKLf2sUv4sALWnm7mSLjvlc6k3Ge20MppLVpfl6PRbAqM3JvGppA7ytT5vmUZ2DGmqtve8i30I+FOoYVdbh0wyZ5XKHWYjn8Ljqzl6lDUUXvkPhgRMuMTK9vRGNLIqYQ8OAJmcyFBuYHHzduo2T+iq6c3sQlJd62ZS7bttGn5wGD1+9pDD5whJcVfFByzjSw8IEJXr6sL7q28Tx+Vp/e6BTsxUCignu1bW/jW9nOw0bW5kGLLS+8MLPTUxc7cHEV16Zqug2miOVHbd5IAmJIGnigDGsz1YYQ/UylTF3989pA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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