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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bPUGyJe8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6FFFC606A33D; Wed, 4 Nov 2026 09:11:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=bPUGyJe8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD4141F00A16; Wed, 4 Nov 2026 09:11:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793783492; bh=+BWGMpp+CGdBx3er7fkKiPSgFKGZi9UN3j89ZX4ZK/I=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=bPUGyJe8jTsIlbF1xVTN5nX4l/yeQqqr6KUSLqOk5CwA8zaane6up/uXHy/A6ETFN 8GMdYQkC/9pvmhBP2zcSqtRvRTHOksDMwvx7gtNR3V/dSa5XbcrFjusMb5bbHlPAqY FtbHm8MMjkmKP//Sey/LKddohMLPyRf4C7s+5IntPmGQ+G5m0rp18ZxLjCBmoTbsqX 6+sBf9cofe3crMJ9E65oq/xyI3vlQ9WK8JdqiYXb7nE+wHWgrx4QfKgjh+C53e4xEw hQtZGro3VXx5kNioH4KUnh6d9IwsWjAmh0kD1m7YN8VI3LyBQcu4wnCHz5d6QOS+Jm 8qsGDtkKaCKQw== Message-ID: <45508a75-7549-40e2-a71a-807a824ea026@kernel.org> Date: Wed, 4 Nov 2026 10:11:14 +0100 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 43/47] mm/huge_memory: split huge PUDs when adjusting VMA boundaries To: Lance Yang 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, 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 References: <20261031-fixes_core-v3-43-d6437171ecc3@kernel.org> <20261104031245.9524-1-lance.yang@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 On 11/4/26 04:12, Lance Yang wrote: > > 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 Thanks for the review! Please do keep reviewing, but note that more trailers (including this one) will likely not make it upstream as I am about to prepare the PR to get most of these things here upstream. -- Cheers, David