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b=ec5EmqEi8Tuh9mTsaLR2NyeFZLdI9fBDmozhfEZ4YpGe2RFN2Iyl61G2P5gtlxp3y VTn8OXE3D/Lm/yvrWsIKkTSDETCKnR9MU1VlqG/AbVWvH6JssNSLT2ZuNF2lvdzJJl Ony94uN9+P6ItRlZD0y0VZZMFuLOUSip3ayAhmQXfc6+c2MPRqsMR5nJCUSseJjHCw s1dpzIhmQJsCsqbsPU/z4cgaHimb+rB72zF7FBAVtCWy153opI7bU7Xa16mHsMTG4Z Xxunnz2J25EbvKNvep0Ylb+cyXxLf8CUUmfUw1r3cAq+/A+4ghhKTzGg1e7lBk2fEM 38QyluppoKojw== Message-ID: <74f0b99f-5184-448f-a5b0-fb8c827028ee@kernel.org> Date: Fri, 27 Feb 2026 21:55:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] perf/events: Replace READ_ONCE() with standard pgtable accessors To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260227062744.2215491-1-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: <20260227062744.2215491-1-anshuman.khandual@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 8D288160002 X-Rspamd-Server: rspam08 X-Stat-Signature: 933qog3wgerrfo1eoeogaimnxd4mwrjq X-HE-Tag: 1772225750-655149 X-HE-Meta: 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 irrNuYUC 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 07:27, Anshuman Khandual wrote: > Replace raw READ_ONCE() dereferences of pgtable entries with corresponding > standard page table accessors pxdp_get() in perf_get_pgtable_size(). These > accessors default to READ_ONCE() on platforms that don't override them. So > there is no functional change on such platforms. > > However arm64 platform is being extended to support 128 bit page tables via > a new architecture feature i.e FEAT_D128 in which case READ_ONCE() will not > provide required single copy atomic access for 128 bit page table entries. > Although pxdp_get() accessors can later be overridden on arm64 platform to > extend required single copy atomicity support on 128 bit entries. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Namhyung Kim > Cc: linux-perf-users@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Peter Zijlstra (Intel) > Signed-off-by: Anshuman Khandual > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David