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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 70B99C76195 for ; Mon, 15 Jul 2019 20:36:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 512552145D for ; Mon, 15 Jul 2019 20:36:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731876AbfGOUgZ (ORCPT ); Mon, 15 Jul 2019 16:36:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36816 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729505AbfGOUgZ (ORCPT ); Mon, 15 Jul 2019 16:36:25 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9E07D308FEC0; Mon, 15 Jul 2019 20:36:24 +0000 (UTC) Received: from redhat.com (ovpn-125-108.rdu2.redhat.com [10.10.125.108]) by smtp.corp.redhat.com (Postfix) with SMTP id 26AFF608CA; Mon, 15 Jul 2019 20:36:17 +0000 (UTC) Date: Mon, 15 Jul 2019 16:36:11 -0400 From: "Michael S. Tsirkin" To: Thiago Jung Bauermann Cc: virtualization@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jason Wang , Christoph Hellwig , David Gibson , Alexey Kardashevskiy , Paul Mackerras , Benjamin Herrenschmidt , Ram Pai , Jean-Philippe Brucker , Michael Roth , Mike Anderson Subject: Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted Message-ID: <20190715163453-mutt-send-email-mst@kernel.org> References: <20190323165456-mutt-send-email-mst@kernel.org> <87a7go71hz.fsf@morokweng.localdomain> <20190520090939-mutt-send-email-mst@kernel.org> <877ea26tk8.fsf@morokweng.localdomain> <20190603211528-mutt-send-email-mst@kernel.org> <877e96qxm7.fsf@morokweng.localdomain> <20190701092212-mutt-send-email-mst@kernel.org> <87d0id9nah.fsf@morokweng.localdomain> <20190715103411-mutt-send-email-mst@kernel.org> <874l3nnist.fsf@morokweng.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <874l3nnist.fsf@morokweng.localdomain> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 15 Jul 2019 20:36:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 15, 2019 at 05:29:06PM -0300, Thiago Jung Bauermann wrote: > > Michael S. Tsirkin writes: > > > On Sun, Jul 14, 2019 at 02:51:18AM -0300, Thiago Jung Bauermann wrote: > >> > >> > >> Michael S. Tsirkin writes: > >> > >> > So this is what I would call this option: > >> > > >> > VIRTIO_F_ACCESS_PLATFORM_IDENTITY_ADDRESS > >> > > >> > and the explanation should state that all device > >> > addresses are translated by the platform to identical > >> > addresses. > >> > > >> > In fact this option then becomes more, not less restrictive > >> > than VIRTIO_F_ACCESS_PLATFORM - it's a promise > >> > by guest to only create identity mappings, > >> > and only before driver_ok is set. > >> > This option then would always be negotiated together with > >> > VIRTIO_F_ACCESS_PLATFORM. > >> > > >> > Host then must verify that > >> > 1. full 1:1 mappings are created before driver_ok > >> > or can we make sure this happens before features_ok? > >> > that would be ideal as we could require that features_ok fails > >> > 2. mappings are not modified between driver_ok and reset > >> > i guess attempts to change them will fail - > >> > possibly by causing a guest crash > >> > or some other kind of platform-specific error > >> > >> I think VIRTIO_F_ACCESS_PLATFORM_IDENTITY_ADDRESS is good, but requiring > >> it to be accompanied by ACCESS_PLATFORM can be a problem. One reason is > >> SLOF as I mentioned above, another is that we would be requiring all > >> guests running on the machine (secure guests or not, since we would use > >> the same configuration for all guests) to support it. But > >> ACCESS_PLATFORM is relatively recent so it's a bit early for that. For > >> instance, Ubuntu 16.04 LTS (which is still supported) doesn't know about > >> it and wouldn't be able to use the device. > > > > OK and your target is to enable use with kernel drivers within > > guests, right? > > Right. > > > My question is, we are defining a new flag here, I guess old guests > > then do not set it. How does it help old guests? Or maybe it's > > not designed to ... > > Indeed. The idea is that QEMU can offer the flag, old guests can reject > it (or even new guests can reject it, if they decide not to convert into > secure VMs) and the feature negotiation will succeed with the flag > unset. OK. And then what does QEMU do? Assume guest is not encrypted I guess? > -- > Thiago Jung Bauermann > IBM Linux Technology Center