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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 0FC17C282CC for ; Tue, 5 Feb 2019 16:14:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD81820844 for ; Tue, 5 Feb 2019 16:14:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729515AbfBEQNz (ORCPT ); Tue, 5 Feb 2019 11:13:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:30918 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729392AbfBEQNv (ORCPT ); Tue, 5 Feb 2019 11:13:51 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 257B0804E9; Tue, 5 Feb 2019 16:13:51 +0000 (UTC) Received: from redhat.com (ovpn-116-138.sin2.redhat.com [10.67.116.138]) by smtp.corp.redhat.com (Postfix) with SMTP id CFDB560BF1; Tue, 5 Feb 2019 16:13:41 +0000 (UTC) Date: Tue, 5 Feb 2019 11:13:39 -0500 From: "Michael S. Tsirkin" To: Christoph Hellwig Cc: Thiago Jung Bauermann , Jason Wang , virtualization@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, David Gibson , Alexey Kardashevskiy , Paul Mackerras , Benjamin Herrenschmidt , Ram Pai , Jean-Philippe Brucker Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190205111128-mutt-send-email-mst@kernel.org> References: <87zhrj8kcp.fsf@morokweng.localdomain> <87womn8inf.fsf@morokweng.localdomain> <20190129134750-mutt-send-email-mst@kernel.org> <6c68f7f7-1b28-6eba-9b8b-2c32efac9701@redhat.com> <20190129213137-mutt-send-email-mst@kernel.org> <20190130074427.GA29516@lst.de> <875ztzxvw2.fsf@morokweng.localdomain> <20190204152416-mutt-send-email-mst@kernel.org> <20190205072407.GA4311@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190205072407.GA4311@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 05 Feb 2019 16:13:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 05, 2019 at 08:24:07AM +0100, Christoph Hellwig wrote: > On Mon, Feb 04, 2019 at 04:38:21PM -0500, Michael S. Tsirkin wrote: > > It was designed to make, when set, as many guests as we can work > > correctly, and it seems to be successful in doing exactly that. > > > > Unfortunately there could be legacy guests that do work correctly but > > become slow. Whether trying to somehow work around that > > can paint us into a corner where things again don't > > work for some people is a question worth discussing. > > The other problem is that some qemu machines just throw passthrough > devices and virtio devices on the same virtual PCI(e) bus, and have a > common IOMMU setup for the whole bus / root port / domain. I think > this is completely bogus, but unfortunately it is out in the field. > > Given that power is one of these examples I suspect that is what > Thiago referes to. But in this case the answer can't be that we > pile on hack ontop of another, but instead introduce a new qemu > machine that separates these clearly, and make that mandatory for > the secure guest support. That could we one approach, assuming one exists that guests already support. -- MST