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b=n+h/dgKkcBlo/dGQjj1ub3s9bjOa0M2la6urtdxD0te37aVSmCofz0hyWaifbPk20 mS8IHjwYOyPvqcGFKrUnRefPCHeAQFySphnvGxKPQLj4KzCYeGzPYq+BCR3cj4vCA6 viFy8LB1SAvbHyu/PXVcxGxXFGzLV4lIpsWxWktEtHo8/sTXJB2/0K71s+fSdPIhB3 nX9RflZcxKhiUeUSMoVeyVE4jZT8zOB7eNZFF7cKPGRJ0xB0z3EYGyPa61BN7W9knN 4GxyBMUDop4P3Sk7/axoqTQA3bJ8OeJqcVc3VI47d8arWIzRyxwP4RvDi6JVUKjcj3 qAM2UyRRNtqIg== Message-ID: <3603c37b-95b1-4d29-ab6f-fa3360dc17db@kernel.org> Date: Fri, 12 Jun 2026 13:14:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V2 0/3] lib/vsprintf: Add support for pgtable entries To: Matthew Wilcox , Andy Shevchenko Cc: Anshuman Khandual , linux-mm@kvack.org, Rasmus Villemoes , Sergey Senozhatsky , Petr Mladek , Steven Rostedt , Jonathan Corbet , Andrew Morton , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org References: <20260610043545.3725735-1-anshuman.khandual@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 89DA0160015 X-Stat-Signature: ngub1jmjgd869faaj1une88bapaw49hn X-Rspam-User: X-HE-Tag: 1781262857-172078 X-HE-Meta: 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 rUalJQXo 7FjfNLQXQzwT50bI6KtyGUNOUNhNZfL480FAGscvCi2uFLtqVrF/i9WK7FCBN19289LYtEm5zOGZIUhEyYA09y3A/NFNxvegK9+khcaVd2pyikyjzbRloOBtl4y+7W+w0ZrPP+eFrtBJGXR+eBgtwo8gYD7gVOFv1ftCwDyzwzkafywmjjwsKxFFEEtakWIuRxoavoYEURF5be0prUuAnvvPfUS59LpwiDyzjbHMAl+anWJvJtTGXo9kXGjpI/3Aknkd6IzJYW8K7J8mIsYmEHaXr2GVLdUCNtqCxw/hkct8TcTRbHnbAjrY201d4f/HPwtWcimg4Z4XhcnVpBllQ8GZj9Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/11/26 21:37, Matthew Wilcox wrote: > On Thu, Jun 11, 2026 at 10:33:35PM +0300, Andy Shevchenko wrote: >> On Thu, Jun 11, 2026 at 08:15:57PM +0100, Matthew Wilcox wrote: >>> >>> You didn't address my objection here: >>> >>> https://lore.kernel.org/linux-mm/aFQP8LzVMctf6XH5@casper.infradead.org/ >>> >>> ie there is now no typechecking possible. So you've made it more >>> dangerous. I reiterate my NACK to the concept, not to the implementation. >> >> But this is more of a global question, how do we check the validity of >> the parameters of pointer extensions in the kernel? Does anybody go to >> commit into GCC plugin or so for this job? > > I agree that it's a global question that it would be great for somebody > to answer. But it's specifically a problem for this patchset because: > > - It's really easy to get confused about which page table level you're > working on. And hugetlbfs deliberately increases that confusion. Yeah ... so far I was assuming that for hugetlb, all relevant entries (what we call a PTE although it isn't ....) would have to be the same size. I mean, at least in the callers they are the same size (pte_t) > - Different levels of the page tables actually do have different sizes > on some architectures, so if you think you're looking at a pointer to a > 64-bit quantity when it's really a pointer to a 32-bit quantity, things > Will Go Wrong (or vice-versa. And some architctures are big-endian) I see your point with the pass-by-pointer. > - But on x86-64, Everything Is Fine because all levels of the page table > are basically identical, so you'll never notice there's a problem. I assume on most architectures. Let's see if we can stop printing that information completely, so we can avoid messing with this at all. -- Cheers, David