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b=cfweDhmY3uzvwT/ivKj11445D9BHzpepvwDhcWWBY0Ax9ECQOnkIy2JdCFBTcQh+O OL5bc+sjjh6g1WZpz3gftwLq3vURxlcGhKoQlk3w1QcGdY5BCWKL3qNxOepmz9mnHw hLf8zsYFvcrlxKTU2kIii7Q9VvyYogkTc9t2AndndPnTcQ+2jYibLpoixg1z4E2qHw 3ZKVmPO5NGQEfdRfmdvnPu4KES5JWkbJaMtwRLpstX//I7D3xenCII9qgmhmfLP9zx zh226Qdu3vaRu6SDP2qO8V1dLSuWZZGFYZ3k5Es3tJa5Lf3fTt4n+n4Z/Z+Ijpxi/J QSIKNgtpyQ+zA== Message-ID: Date: Mon, 6 Jul 2026 15:49:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 6/8] string: introduce memcpy_nt() helpers To: Li Zhe Cc: akpm@linux-foundation.org, apopple@nvidia.com, arnd@arndb.de, bp@alien8.de, dave.hansen@linux.intel.com, kees@kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org, x86@kernel.org References: <20260706115313.50524-1-lizhe.67@bytedance.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: <20260706115313.50524-1-lizhe.67@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: jb5r15gdfcpoqdts4f38ti189gkr9sxp X-Rspamd-Queue-Id: 580424000C X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783345768-672179 X-HE-Meta: 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 UOXT7mL+ Q8+IQuTwAMyLntfZBdHaB09J0BtLtdjNELu1vWv7VLl4GvtSBu5wMhP4d0nBv2ViWBvTN6jH+U4O6gtAYp10tnPUz7ActmHWrwLFGgW1T8IQmCJtnrpNNuzuboDWWEr7GBImAvkC8V7j4C3aCO9rSmfYjDfe3jaHKb4/YJyV4gfKwbcHp7pmiB+hCSHg0lu4+qKnvDrJ/zaX3cQ/aSrFHyZO+Crfxp1MUiKaQAZ9ZDMVnELGjyRPOuDF3b4/0mbJYdWKElvLgPrSU5ahzLnT8sbirsZ6Ci/DSOry0fu8Ph7BHxRQcxvS8B5T6QsPmxC2VSx4S7gwwEeIqfZdnRsIjS6NiOgdmey+3Qw6B Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/6/26 13:53, Li Zhe wrote: > On Mon, Jul 6, 2026 at 11:18:48AM +0200, david@kernel.org wrote: > >>> + >>> +#define __HAVE_ARCH_MEMCPY_NT 1 >>> +/* >>> + * Reuse the existing x86 flushcache backend as the nt copy primitive. >>> + * Callers pair it with memcpy_nt_drain() when later stores must be >>> + * ordered after the copy. >>> + */ >>> +static __always_inline void memcpy_nt(void *dst, const void *src, size_t cnt) >>> +{ >>> + memcpy_flushcache(dst, src, cnt); >>> +} >> >> In particular if you end up with a single function (that jsut requires a write >> memory barrier afterwards), please make this >> >> #define memcpy_nt memcpy_nt >> >> instead. > > Thanks for the review. > > Just to make sure I understood this correctly: do you mean that, rather > than using a separate __HAVE_ARCH_MEMCPY_NT feature macro, you would > prefer the usual self-macro override pattern, with > > #define memcpy_nt memcpy_nt > > in arch/x86/include/asm/string_64.h and the generic fallback kept under > #ifndef memcpy_nt in include/linux/string.h? Yes, that's what Linus suggested as the preferred way for single functions when it came up in different context recently. -- Cheers, David