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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 812C1C433F5 for ; Sat, 18 Sep 2021 11:39:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0A4C961260 for ; Sat, 18 Sep 2021 11:39:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0A4C961260 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 94F7C6B0071; Sat, 18 Sep 2021 07:39:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8FFCB900002; Sat, 18 Sep 2021 07:39:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C6CA6B0073; Sat, 18 Sep 2021 07:39:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0171.hostedemail.com [216.40.44.171]) by kanga.kvack.org (Postfix) with ESMTP id 6CA896B0071 for ; Sat, 18 Sep 2021 07:39:58 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 26C1D1824229D for ; Sat, 18 Sep 2021 11:39:58 +0000 (UTC) X-FDA: 78600500076.21.CD47117 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf30.hostedemail.com (Postfix) with ESMTP id CD63AE001985 for ; Sat, 18 Sep 2021 11:39:57 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 95D1B61244; Sat, 18 Sep 2021 11:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631965196; bh=BzRo8ApXY7trnCJ4YSP1u1W1GLdyywjRf4lzNkQ9II0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Rk5GtKtSkrKOa37Armo/WbiMF40SMYf8Z/yR7wQLJ4tq9WvlEnBIZRkh/v7avyV+1 F3jWBZaBjcyK3s4MIFrizkLVTv3itkj4orR1Mq67lK2PEa9dn09GJS3+kyQJ5Ek1k0 jDipUzBhNz72d8ZC/6axWHaQV/QZJgpAOpSiGdC+SlkNm4f/n/D8CKTX2p15oT2QM2 0TAsWlAbZWDnB4N4h513W1swEMpj+nQs7sW0PNjH5scL+6KIqqW+Tn+1ZyL6RhO3OQ UcZfnBAVhOCmMQjNufRvsycfCDXV/v2wltAP2a8387XaTVOCoMThTvANyB2vffLdSt dxUydgSy7D22Q== Date: Sat, 18 Sep 2021 14:39:49 +0300 From: Mike Rapoport To: Christoph Hellwig 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 Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases) Message-ID: References: <20210824173741.GC623@arm.com> <0908ce39-7e30-91fa-68ef-11620f9596ae@arm.com> <60a11eba-2910-3b5f-ef96-97d4556c1596@redhat.com> <20210825102044.GA3420@arm.com> <20210918051843.GA16104@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: CD63AE001985 X-Stat-Signature: 4wtacj5drqpeygmxxpk3tw6nprzetyxp Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Rk5GtKtS; spf=pass (imf30.hostedemail.com: domain of rppt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-HE-Tag: 1631965197-745034 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 11:37:22AM +0300, Mike Rapoport wrote: > On Sat, Sep 18, 2021 at 07:18:43AM +0200, Christoph Hellwig wrote: > > 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. > > Indeed :( > But pfn_valid is plain wrong... > I'll keep digging. I did some more archaeology and it that check for pfn_valid() was requested by arm folks because their MMU may have troubles with alias mappings with different attributes and so they made the check to use a false assumption that pfn_valid() == "RAM". As this WARN_ON(pfn_valid()) is only present in dma_map_resource() it's probably safe to drop it entirely. Otherwise the simplest way would be to hide it behind something like ARCH_WANTS_DMA_NOT_RAM and make arm/arm64 select it. Thoughts? -- Sincerely yours, Mike.