From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE780C433E1 for ; Wed, 27 May 2020 01:06:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 987B2207CB for ; Wed, 27 May 2020 01:06:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728091AbgE0BG5 (ORCPT ); Tue, 26 May 2020 21:06:57 -0400 Received: from mail.loongson.cn ([114.242.206.163]:53282 "EHLO loongson.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727852AbgE0BG4 (ORCPT ); Tue, 26 May 2020 21:06:56 -0400 Received: from [10.20.42.25] (unknown [10.20.42.25]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9AxJuoOvc1eSHI5AA--.349S3; Wed, 27 May 2020 09:06:23 +0800 (CST) Subject: Re: [PATCH v6 1/4] MIPS: Do not flush tlb page when updating PTE entry To: Andrew Morton References: <1590375160-6997-1-git-send-email-maobibo@loongson.cn> <20200525144241.f0e55183a846607cdbb0d819@linux-foundation.org> Cc: Thomas Bogendoerfer , Jiaxun Yang , Huacai Chen , Paul Burton , Dmitry Korotin , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Stafford Horne , Steven Price , Anshuman Khandual , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, Mike Rapoport , Sergei Shtylyov , "Maciej W. Rozycki" , linux-mm@kvack.org, David Hildenbrand From: maobibo Message-ID: Date: Wed, 27 May 2020 09:06:22 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20200525144241.f0e55183a846607cdbb0d819@linux-foundation.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-CM-TRANSID: AQAAf9AxJuoOvc1eSHI5AA--.349S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Kw18JFy5CF13ZF1rZr17Awb_yoW8GFWDpF ZrJan5ta97Wry8CrW8Zwsa9FZIy397Jr4vgrn8GrZIv3W5t3WfKrsxG3yrtas5XryUG3W8 tr40grsrXw1jg37anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUU9Ib7Iv0xC_Kw4lb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_JFI_Gr1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4 A2jsIEc7CjxVAFwI0_Gr0_Gr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI 64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r106r15McIj6I8E87Iv67AKxVWUJVW8Jw Am72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l c7I2V7IY0VAS07AlzVAYIcxG8wCY02Avz4vE-syl42xK82IYc2Ij64vIr41l4I8I3I0E4I kC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWU WwC2zVAF1VAY17CE14v26r4a6rW5MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr 0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVW8 JVW3JwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJb IYCTnIWIevJa73UjIFyTuYvjxUqhvKUUUUU X-CM-SenderInfo: xpdruxter6z05rqj20fqof0/ Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/26/2020 05:42 AM, Andrew Morton wrote: > On Mon, 25 May 2020 10:52:37 +0800 Bibo Mao wrote: > >> It is not necessary to flush tlb page on all CPUs if suitable PTE >> entry exists already during page fault handling, just updating >> TLB is fine. >> >> Here redefine flush_tlb_fix_spurious_fault as empty on MIPS system. >> >> ... >> >> --- a/arch/mips/include/asm/pgtable.h >> +++ b/arch/mips/include/asm/pgtable.h >> @@ -478,6 +478,8 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot) >> return __pgprot(prot); >> } >> >> +#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0) >> + > > static inline C would be preferred, if that works. For a number of reasons: > > - looks nicer > > - more likely to get a code comment (for some reason) > > - adds typechecking. So right now a MIPS developer could do > > struct wibble a; > struct wobble b; > > flush_tlb_fix_spurious_fault(&a, &b); > > and there would be no compiler warning. Then the code gets merged > upstream and in come the embarrassing emails! > > - avoids unused-var warnings > > foo() > { > struct address_space a; > struct vm_area_struct v; > > flush_tlb_fix_spurious_fault(&v, &a); > } > > will generate unused-variable warnings if > flush_tlb_fix_spurious_fault() is a macro. Making > flush_tlb_fix_spurious_fault() inlined C prevents this. > Sure, I will modify this and send another version.