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=-5.2 required=3.0 tests=BAYES_00, 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 EC1ADC433EF for ; Sat, 18 Sep 2021 05:18:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7877F610D1 for ; Sat, 18 Sep 2021 05:18:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7877F610D1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 15FFE900002; Sat, 18 Sep 2021 01:18:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 10FF76B0072; Sat, 18 Sep 2021 01:18:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F40B3900002; Sat, 18 Sep 2021 01:18:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id E25806B0071 for ; Sat, 18 Sep 2021 01:18:47 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id A17613233B for ; Sat, 18 Sep 2021 05:18:47 +0000 (UTC) X-FDA: 78599539494.24.8AA0B6B Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf13.hostedemail.com (Postfix) with ESMTP id 1C21C1032228 for ; Sat, 18 Sep 2021 05:18:46 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id A44E867357; Sat, 18 Sep 2021 07:18:43 +0200 (CEST) Date: Sat, 18 Sep 2021 07:18:43 +0200 From: Christoph Hellwig To: Mike Rapoport Cc: Catalin Marinas , David Hildenbrand , Robin Murphy , Alex Bee , Will Deacon , Andrew Morton , Anshuman Khandual , Linux Kernel Mailing List , linux-mm@kvack.org, Linux ARM , Christoph Hellwig Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases) Message-ID: <20210918051843.GA16104@lst.de> References: <20210824173741.GC623@arm.com> <0908ce39-7e30-91fa-68ef-11620f9596ae@arm.com> <60a11eba-2910-3b5f-ef96-97d4556c1596@redhat.com> <20210825102044.GA3420@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Stat-Signature: q1fkdxhwh7f85ohrg5nkdtobioxm8fuc Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=none; spf=none (imf13.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1C21C1032228 X-HE-Tag: 1631942326-409441 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: On Sat, Sep 18, 2021 at 12:22:47AM +0300, Mike Rapoport wrote: > I did some digging and it seems that the most "generic" way to check if a > page is in RAM is page_is_ram(). It's not 100% bullet proof as it'll give > false negatives for architectures that do not register "System RAM", but > those are not using dma_map_resource() anyway and, apparently, never would. The downside of page_is_ram is that it looks really expensiv for something done at dma mapping time.