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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 04CA1C2D0EA for ; Wed, 8 Apr 2020 09:01:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D69BE20768 for ; Wed, 8 Apr 2020 09:01:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727302AbgDHJBQ (ORCPT ); Wed, 8 Apr 2020 05:01:16 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:12624 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726663AbgDHJBP (ORCPT ); Wed, 8 Apr 2020 05:01:15 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 58A6D33585B02A6E0622; Wed, 8 Apr 2020 17:01:09 +0800 (CST) Received: from [127.0.0.1] (10.173.220.25) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.487.0; Wed, 8 Apr 2020 17:01:01 +0800 Subject: Re: [RFC PATCH v5 4/8] mm: tlb: Pass struct mmu_gather to flush_pmd_tlb_range From: Zhenyu Ye To: Peter Zijlstra CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20200331142927.1237-1-yezhenyu2@huawei.com> <20200331142927.1237-5-yezhenyu2@huawei.com> <20200331151331.GS20730@hirez.programming.kicks-ass.net> <20200401122004.GE20713@hirez.programming.kicks-ass.net> <53675fb9-21c7-5309-07b8-1bbc1e775f9b@huawei.com> <20200402163849.GM20713@hirez.programming.kicks-ass.net> Message-ID: <1770a141-3c97-94df-eac9-2d1f537516b1@huawei.com> Date: Wed, 8 Apr 2020 17:00:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.220.25] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 2020/4/3 13:14, Zhenyu Ye wrote: > Hi Peter, > > On 2020/4/3 0:38, Peter Zijlstra wrote: >> On Thu, Apr 02, 2020 at 07:24:04PM +0800, Zhenyu Ye wrote: >>> Thanks for your detailed explanation. I notice that you used >>> `tlb_end_vma` replace `flush_tlb_range`, which will call `tlb_flush`, >>> then finally call `flush_tlb_range` in generic code. However, some >>> architectures define tlb_end_vma|tlb_flush|flush_tlb_range themselves, >>> so this may cause problems. >>> >>> For example, in s390, it defines: >>> >>> #define tlb_end_vma(tlb, vma) do { } while (0) >>> >>> And it doesn't define it's own flush_pmd_tlb_range(). So there will be >>> a mistake if we changed flush_pmd_tlb_range() using tlb_end_vma(). >>> >>> Is this really a problem or something I understand wrong ? >> >> If tlb_end_vma() is a no-op, then tlb_finish_mmu() will do: >> tlb_flush_mmu() -> tlb_flush_mmu_tlbonly() -> tlb_flush() >> >> And s390 has tlb_flush(). >> >> If tlb_end_vma() is not a no-op and it calls tlb_flush_mmu_tlbonly(), >> then tlb_finish_mmu()'s invocation of tlb_flush_mmu_tlbonly() will >> terniate early due o no flags set. >> >> IOW, it should all just work. >> >> >> FYI the whole tlb_{start,end}_vma() thing is a only needed when the >> architecture doesn't implement tlb_flush() and instead default to using >> flush_tlb_range(), at which point we need to provide a 'fake' vma. >> >> At the time I audited all architectures and they only look at VM_EXEC >> (to do $I invalidation) and VM_HUGETLB (for pmd level invalidations), >> but I forgot which architectures that were. > > Many architectures, such as alpha, arc, arm and so on. > I really understand why you hate making vma->vm_flags more important for > tlbi :). > >> But that is all legacy code; eventually we'll get all archs a native >> tlb_flush() and this can go away. >> > > Thanks for your reply. Currently, to enable the TTL feature, extending > the flush_*tlb_range() may be more convenient. > I will send a formal PATCH soon. > > Thanks, > Zhenyu > I had sent [PATCH v1] a few days ago[1]. Do you have time to review my changes? Are those changes appropriate? Waiting for your suggestion. [1] https://lore.kernel.org/linux-arm-kernel/20200403090048.938-1-yezhenyu2@huawei.com/ Thanks, Zhenyu