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 78A55C18E5B for ; Wed, 25 Mar 2020 08:37:50 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2B3FF206F6 for ; Wed, 25 Mar 2020 08:37:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2B3FF206F6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 0632C88253; Wed, 25 Mar 2020 08:37:50 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PCekhSxAfm3l; Wed, 25 Mar 2020 08:37:49 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 8EADC88252; Wed, 25 Mar 2020 08:37:49 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6F1CBC1D74; Wed, 25 Mar 2020 08:37:49 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id E089AC0177 for ; Wed, 25 Mar 2020 08:37:46 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id D337288253 for ; Wed, 25 Mar 2020 08:37:46 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id w7bwYwXPBW8k for ; Wed, 25 Mar 2020 08:37:45 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by hemlock.osuosl.org (Postfix) with ESMTPS id 5DBFC88252 for ; Wed, 25 Mar 2020 08:37:45 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 8C21B68BFE; Wed, 25 Mar 2020 09:37:40 +0100 (CET) Date: Wed, 25 Mar 2020 09:37:40 +0100 From: Christoph Hellwig To: Alexey Kardashevskiy Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device Message-ID: <20200325083740.GC21605@lst.de> References: <20200320141640.366360-1-hch@lst.de> <20200320141640.366360-2-hch@lst.de> <2f31d0dd-aa7e-8b76-c8a1-5759fda5afc9@ozlabs.ru> <20200323083705.GA31245@lst.de> <20200323085059.GA32528@lst.de> <87sghz2ibh.fsf@linux.ibm.com> <20200323172256.GB31269@lst.de> <20200324075402.GJ23447@lst.de> <41975da3-3a4a-fc3c-2b90-8d607cf220e6@ozlabs.ru> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <41975da3-3a4a-fc3c-2b90-8d607cf220e6@ozlabs.ru> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: Greg Kroah-Hartman , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, "Aneesh Kumar K.V" , linuxppc-dev@lists.ozlabs.org, Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Mar 25, 2020 at 03:51:36PM +1100, Alexey Kardashevskiy wrote: > >> This is for persistent memory which you can DMA to/from but yet it does > >> not appear in the system as a normal memory and therefore requires > >> special handling anyway (O_DIRECT or DAX, I do not know the exact > >> mechanics). All other devices in the system should just run as usual, > >> i.e. use 1:1 mapping if possible. > > > > On other systems (x86 and arm) pmem as long as it is page backed does > > not require any special handling. This must be some weird way powerpc > > fucked up again, and I suspect you'll have to suffer from it. > > > It does not matter if it is backed by pages or not, the problem may also > appear if we wanted for example p2p PCI via IOMMU (between PHBs) and > MMIO might be mapped way too high in the system address space and make > 1:1 impossible. How can it be mapped too high for a direct mapping with a 64-bit DMA mask? _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu