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b=fm4pYk+i6DilsXsT+t8GY4iXYWcW035fNURZeBfTqXB9B2RHLiHuFxqigp1rueLf2 IGKW4LWsJv2ucGAUoKuh2azO8SS5Wre66FjKiCABx/HucXfyegCmGc9lzI6vXZm9TK IRIn/uNZIhUCkHmI5GvnB0izbKU55WHY8/qhSYDgLF+SJ/S2EgfLoWg9Cy++NZmfVV zBhwO2uVX1GHHK9yz42oCR5YFqm6oBIxDibRsv1V8zutdmVYIKkkil68x+IhfAdKQ3 G2j6eq6FwzrPCG9IfEdd/fZKO+YrDfABRPtn4RywDcud+oDOGYsONZgdcI5cfhD47D KWN2m7RrTEYHg== Message-ID: Date: Wed, 8 Apr 2026 14:13:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V1 00/16] arm64/mm: Enable 128 bit page table entries To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , Mike Rapoport , Linu Cherian , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260224051153.3150613-1-anshuman.khandual@arm.com> <8d2c9ecb-ae33-42f2-a8ed-66b3286b9286@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <8d2c9ecb-ae33-42f2-a8ed-66b3286b9286@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 617D2A0013 X-Stat-Signature: 5rub1xhyzd1pdjhdukptpshiuanh667k X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775650423-57731 X-HE-Meta: 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 OFCLqNDb fydEVthcaJWpmb/jfHNpCu0mevCtkgSoiCvDZn82E+c55aXhuDoEzuuK66/cdX9cMNBMJUEeA7kxe34+GenBgDmI0kYa6XAV+ohTc6Kp3j3l6GlFqx2c5DoSAnTLdAM0BKmyIJNs8OnUB1u/286xpO3vLX7CgEJh0oj31zNvwyqCrXi5sKLoKh/KIAXXV60EIo3v39WuCBiGWEOJUexENSVn/Jhu+yGhd9lY5YnB/mpG6QmWyNl/BAe0idD+9xctOj7v3 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/8/26 12:53, Anshuman Khandual wrote: > On 07/04/26 8:14 PM, David Hildenbrand (Arm) wrote: >> On 2/24/26 06:11, Anshuman Khandual wrote: >>> FEAT_D128 is a new arm architecture feature adding support for VMSAv9-128 >>> translation system. FEAT_D128 is an optional feature from ARMV9.3 onwards. >>> So with this feature arm64 platforms could have two different translation >>> systems, VMSAv8-64 and VMSAv9-128 could selectively be enabled. >>> >>> FEAT_D128 adds 128 bit page table entries, thus supporting larger physical >>> and virtual address range while also expanding available room for more MMU >>> management feature bits both for HW and SW. >>> >>> This series has been split into two parts. Generic MM changes followed by >>> arm64 platform changes, finally enabling D128 with a new config ARM64_D128. >>> >>> READ_ONCE() on page table entries get routed via level specific pxdp_get() >>> helpers which platforms could then override when required. These accessors >>> on arm64 platform help in ensuring page table accesses are performed in an >>> atomic manner while reading 128 bit page table entries. >>> >>> All ARM64_VA_BITS and ARM64_PA_BITS combinations for all page sizes are now >>> supported both on D64 and D128 translation regimes. Although new 56 bits VA >>> space is not yet supported. Similarly FEAT_D128 skip level is not supported >>> currently. >>> >>> Basic page table geometry has been changed with D128 as there are now fewer >>> entries per level. Please refer to the following table for leaf entry sizes >>> >>> D64 D128 >>> ------------------------------------------------ >>> | PAGE_SIZE | PMD | PUD | PMD | PUD | >>> -----------------------------|-----------------| >>> | 4K | 2M | 1G | 1M | 256M | >>> | 16K | 32M | 64G | 16M | 16G | >>> | 64K | 512M | 4T | 256M | 1T | >>> ------------------------------------------------ >>> >> >> Interesting. That means user space will have it even harder to optimize >> for THP sizes. >> >> What's the effect on cont-pte? Do they still span the same number of >> entries and there is effectively no change? > > The numbers are the same for 4K base page size but will need > some changes for 16K and 64K base page sizes. Something that > git missed in this series, will fix it. Oh, and it would be great to also clearly spell out the effect on hugetlb as well. I assume the available hugetlb sizes will change as well. -- Cheers, David