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 1774CC35656 for ; Fri, 21 Feb 2020 16:35:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC28B208E4 for ; Fri, 21 Feb 2020 16:35:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726681AbgBUQf1 (ORCPT ); Fri, 21 Feb 2020 11:35:27 -0500 Received: from verein.lst.de ([213.95.11.211]:56364 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726150AbgBUQf1 (ORCPT ); Fri, 21 Feb 2020 11:35:27 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 1B84A68BFE; Fri, 21 Feb 2020 17:35:24 +0100 (CET) Date: Fri, 21 Feb 2020 17:35:23 +0100 From: Christoph Hellwig To: "Michael S. Tsirkin" Cc: Halil Pasic , Jason Wang , Marek Szyprowski , Robin Murphy , Christoph Hellwig , linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Christian Borntraeger , Janosch Frank , Viktor Mihajlovski , Cornelia Huck , Ram Pai , Thiago Jung Bauermann , David Gibson , "Lendacky, Thomas" , Michael Mueller Subject: Re: [PATCH 2/2] virtio: let virtio use DMA API when guest RAM is protected Message-ID: <20200221163523.GA10054@lst.de> References: <20200220160606.53156-1-pasic@linux.ibm.com> <20200220160606.53156-3-pasic@linux.ibm.com> <20200220154904-mutt-send-email-mst@kernel.org> <20200221141230.13eebc35.pasic@linux.ibm.com> <20200221104901-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200221104901-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 21, 2020 at 10:56:45AM -0500, Michael S. Tsirkin wrote: > > > - DMA API is giving us addresses that are actually also physical > > > addresses > > > > In case of s390 this is given. > > I talked with the power people before > > posting this, and they ensured me they can are willing to deal with > > this. I was hoping to talk abut this with the AMD SEV people here (hence > > the cc). > > We'd need a part of DMA API that promises this though. Platform > maintainers aren't going to go out of their way to do the > right thing just for virtio, and I can't track all arches > to make sure they don't violate virtio requirements. There is no way the DMA API is going to promise that you. All kinds of platforms have offsets to DMA, and they are communicated through interfaces like the device tree or ACPI. But the good thing is that your hypervisors is in control of that, neither the DMA API nor virtio have any business to interfer with that. In fact for harware virtio device we might need such an offset for them to work on lots of SOCs.