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=-0.8 required=3.0 tests=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 EBB86C2D0E8 for ; Tue, 31 Mar 2020 09:45:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B6374208E0 for ; Tue, 31 Mar 2020 09:45:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6374208E0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4D38E6B0032; Tue, 31 Mar 2020 05:45:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 484836B0037; Tue, 31 Mar 2020 05:45:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 372846B006C; Tue, 31 Mar 2020 05:45:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0101.hostedemail.com [216.40.44.101]) by kanga.kvack.org (Postfix) with ESMTP id 1C0456B0032 for ; Tue, 31 Mar 2020 05:45:27 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B98288248047 for ; Tue, 31 Mar 2020 09:45:26 +0000 (UTC) X-FDA: 76655174652.21.skirt12_86cb7f310cd02 X-HE-Tag: skirt12_86cb7f310cd02 X-Filterd-Recvd-Size: 2690 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Tue, 31 Mar 2020 09:45:26 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6081430E; Tue, 31 Mar 2020 02:45:25 -0700 (PDT) Received: from C02TD0UTHF1T.local (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DDBD43F52E; Tue, 31 Mar 2020 02:45:22 -0700 (PDT) Date: Tue, 31 Mar 2020 10:45:11 +0100 From: Mark Rutland To: Andrea Arcangeli Cc: Catalin Marinas , Will Deacon , Rafael Aquini , Mark Salter , Jon Masters , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Michal Hocko , QI Fuli Subject: Re: [PATCH 3/3] arm64: tlb: skip tlbi broadcast Message-ID: <20200331094034.GA1131@C02TD0UTHF1T.local> References: <20200223192520.20808-1-aarcange@redhat.com> <20200223192520.20808-4-aarcange@redhat.com> <20200309112242.GB2487@mbp> <20200314031609.GB2250@redhat.com> <20200316140906.GA6220@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200316140906.GA6220@lakrids.cambridge.arm.com> 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: Hi Andrea, On Mon, Mar 16, 2020 at 02:09:07PM +0000, Mark Rutland wrote: > AFAICT, this series relies on: > > * An ISB completing prior page table walks when updating TTBR. I don't > believe this is necessarily the case, given how things work for an > EL1->EL2 transition where there can be ongoing EL1 walks. I've had confirmation that a DSB is necessary (after the MSR and ISB) to complete any ongoing translation table walks for the stale context. Without a DSB, those walks can observe subsequent stores and encounter the usual set of CONSTRAINED UNPREDICTABLE behaviours (e.g. walking into MMIO with side-effects, continuing from amalgamted entries, etc). Those issues are purely to do with the walk, and apply regardless of whether the resulting translations are architecturally consumed. > * Walks never being initiated for `inactive` contexts within the current > translation regime. e.g. while ASID x is installed, never starting a > walk for ASID y. I can imagine that the architecture may permit a form > of this starting with intermediate walk entries in the TLBs. I'm still chasing this point. Thanks, Mark.