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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 B813FC43331 for ; Thu, 2 Apr 2020 16:39:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E7D82074D for ; Thu, 2 Apr 2020 16:39:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ZDDJU7hB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389863AbgDBQj0 (ORCPT ); Thu, 2 Apr 2020 12:39:26 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:60362 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388555AbgDBQjZ (ORCPT ); Thu, 2 Apr 2020 12:39:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nqbyCH5YSO8hIQBl5BFO0PKfAkJhFfHblJDOEjQg06c=; b=ZDDJU7hB9Y4BeEoEvq0ZWkjyes tWNN5+Q8Aps1yopdwx/p7ZC6pREcjUvJJLCTUIAKT04nXEe3PzZrjvSNYzCVCqQFZRWEazN+c3QTZ xl2RxTS8yF5XbLZkoMHpcMAHS113mDStUTeONM4nTwPGsvJVpNteBsVGMAIFmkxS8mzQfD6te1RaO mDcD9NE4oQrHAR8vMkY2jvhU+ry6apicMyChVMa2J1ugjNeOq7kjtD/iQ/I1U1sph25pL9wiqjf94 XlzEBxuOYYnCJgC3Sq0ClRadrVU0iOj53lr8qxteStNrPPWiLH0W8tPfLtPf+9Bn+a2qafP8SLIcm 9PmisVRQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jK2rk-0007bD-EF; Thu, 02 Apr 2020 16:38:52 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7F0B03056DE; Thu, 2 Apr 2020 18:38:49 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 423372B0DE293; Thu, 2 Apr 2020 18:38:49 +0200 (CEST) Date: Thu, 2 Apr 2020 18:38:49 +0200 From: Peter Zijlstra To: Zhenyu Ye Cc: mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, npiggin@gmail.com, arnd@arndb.de, rostedt@goodmis.org, maz@kernel.org, suzuki.poulose@arm.com, tglx@linutronix.de, yuzhao@google.com, Dave.Martin@arm.com, steven.price@arm.com, broonie@kernel.org, guohanjun@huawei.com, corbet@lwn.net, vgupta@synopsys.com, tony.luck@intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, arm@kernel.org, xiexiangyou@huawei.com, prime.zeng@hisilicon.com, zhangshaokun@hisilicon.com, kuhn.chenqun@huawei.com Subject: Re: [RFC PATCH v5 4/8] mm: tlb: Pass struct mmu_gather to flush_pmd_tlb_range Message-ID: <20200402163849.GM20713@hirez.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53675fb9-21c7-5309-07b8-1bbc1e775f9b@huawei.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. But that is all legacy code; eventually we'll get all archs a native tlb_flush() and this can go away.