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[2003:d8:2f0a:2e00:89cb:c7f0:82f2:e43c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8e1f4edsm5112095f8f.83.2025.07.11.12.03.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Jul 2025 12:03:12 -0700 (PDT) Message-ID: Date: Fri, 11 Jul 2025 21:03:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 10/14] x86/mm: Simplify clear_page_* To: Ankur Arora Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20250710005926.1159009-1-ankur.a.arora@oracle.com> <20250710005926.1159009-11-ankur.a.arora@oracle.com> <377d74d6-a7f9-4e94-9276-168a26d49210@redhat.com> <874iviprkf.fsf@oracle.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C15B940015 X-Rspamd-Server: rspam07 X-Stat-Signature: egih3cjtnt6fo6qjcrgq9xhcefc1188r X-Rspam-User: X-HE-Tag: 1752260597-16858 X-HE-Meta: U2FsdGVkX19aUgK1Ue9NtIeQr2jI6KPkLQegb6TSxSqfuyhSX+nK7PoLWhXIrWofaJImUU0pIzSS/LcmIZ1Zqc9tHDQNfwcTicMoeA15Zq81Dwivn3i5x1TI15e/DvOjLxFPNpI7kgmM+XGZuK/t/WJMqikO/cb7v824gmQ51EdTJKxdqt84ck8ypqdCyY5QasRtFmT1ZISaz14XdCT3YeTYk8mOE8OJN6aKRBZlZVtLj5J12HyodCFROb38wk15/T5Uudrskc4RF5MNAqP3FeJTAVI+9Xo9zxfoXRV2ZaFNGdbSyZfrAW/nS6yYWfIuhCbVuEveRHKIC1hRmDHY4y9f0b7JVMss8Kw8Q0JQx7YwVMhiYSiUxyeM+P2PW99XokvdAw5WJTq9UvSMUnSQaRURafM+bBldV3KFpDl39sFb4POKEkV/GORVdItZXunFK36RtSPpSkgDuVYCFnVbwULdHGpSNIAqsVAcyAQrcDucWoUMJ/wVnDHg+dPiScqnUwyB3MLo7aiAa0N4Ap4jK4S7sPQYA9+UwIC7FmPzgLvnTMLRfzAbIbYFrmwM5IEBP/ji4MdWpMWMck96X9Ilp3utfE3wRfaWnmR6SRzPA/vuOyndJNqEMUtoXqWg+MrWnEt5Vxk8s5xLu/pbdpt42jbF3pAcUBmnJKc380uVL6xdStsPpWBQECH7KPRfsgmqHwpM6eu9Q5VzEJzHXqdLXVFo454Td9o/8Jv5tUl1w4Qhp3VJ62oQaDxpj8IPc63DbhBTGKWR0x89Hk4uXQqoAyPFfvD05YiFh191oXDzM5IPAuQzugfIDWef1rygp98Vq+S5k+3vRRpLFyIBTaQkhtKbMT7UFEQZNYVfLFt2iSpQ6CNSH4ujarJlJAqFUIcW+55O2IovHNdCLfF/TmuS5YMN8uJ4SXivdMN2y/8T4ufIkwc1+Xm7yb6uKMnUugCncYzY8F8B4mhbRgPPPFf zz8QYdHs 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.07.25 19:26, Ankur Arora wrote: > > David Hildenbrand writes: > >> On 10.07.25 02:59, Ankur Arora wrote: >>> clear_page_rep() and clear_page_erms() are wrappers around "REP; STOS" >>> variations. Inlining gets rid of an unnecessary CALL/RET (which isn't >>> free when using RETHUNK speculative execution mitigations.) >>> Fixup and rename clear_page_orig() to adapt to the changed calling >>> convention. >>> And, add a comment from Dave Hansen detailing various clearing mechanisms >>> used in clear_page(). >>> Signed-off-by: Ankur Arora >>> --- >>> arch/x86/include/asm/page_32.h | 6 +++++ >>> arch/x86/include/asm/page_64.h | 42 ++++++++++++++++++++++++++-------- >>> arch/x86/lib/clear_page_64.S | 39 +++++++------------------------ >>> 3 files changed, 46 insertions(+), 41 deletions(-) >>> diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h >>> index 0c623706cb7e..a8ff43bb9652 100644 >>> --- a/arch/x86/include/asm/page_32.h >>> +++ b/arch/x86/include/asm/page_32.h >>> @@ -17,6 +17,12 @@ extern unsigned long __phys_addr(unsigned long); >>> #include >>> +/* >> >> /** if this was supposed to be kernel doc (which it looks like it is) >> >>> + * clear_page() - clear kernel page. >> >> "clear a kernel page" >> >> Although I am not sure what a "kernel page" is. >> >> Did you mean "clear a page using a kernel virtual address" ? > > Thanks. Yes, this makes way more sense. FWIW, most clear_user_page() will just call clear_page(). The ones that don't, have to deal with the dcache flushing, as the page might have cache alias from another (mm) address space. So clear_page() is just about clearing page content using a kernel virtual address, and clear_user_page() is additionally taking care of any dcache aliases. -- Cheers, David / dhildenb