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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 1088FC433DF for ; Fri, 19 Jun 2020 16:10:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E34B421707 for ; Fri, 19 Jun 2020 16:10:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OzJifZ3H" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391470AbgFSPGi (ORCPT ); Fri, 19 Jun 2020 11:06:38 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:40517 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2391454AbgFSPGg (ORCPT ); Fri, 19 Jun 2020 11:06:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592579194; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lr+LUOaLSBgm41JBpkX79KrfQBxFPphNoXJMk//1n6g=; b=OzJifZ3HrW0zP7g1jhAs49nT9SgA5eYVeWnD7h2xPxrEF2LH00yt+/H38GKbtadKpM5Rbt 5Skr2kr8/D1r1gxV2kJJ4bSqlXPulKWaCi52XF0qVR8CnEE3SQQZeMnvQ4McMOlhhRDWG1 ObgkEKdsdrv/OvjTRSwb/9snIsdGhx0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-112-Nn_I5OnqOAaEp7tXeJv0cQ-1; Fri, 19 Jun 2020 11:06:07 -0400 X-MC-Unique: Nn_I5OnqOAaEp7tXeJv0cQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 178EF106C01C; Fri, 19 Jun 2020 15:06:05 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 13C135C1D0; Fri, 19 Jun 2020 15:05:59 +0000 (UTC) Date: Fri, 19 Jun 2020 16:05:56 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: David Gibson Cc: qemu-devel@nongnu.org, brijesh.singh@amd.com, pair@us.ibm.com, pbonzini@redhat.com, dgilbert@redhat.com, frankja@linux.ibm.com, Eduardo Habkost , kvm@vger.kernel.org, mst@redhat.com, cohuck@redhat.com, david@redhat.com, mdroth@linux.vnet.ibm.com, pasic@linux.ibm.com, qemu-s390x@nongnu.org, qemu-ppc@nongnu.org, Richard Henderson Subject: Re: [PATCH v3 9/9] host trust limitation: Alter virtio default properties for protected guests Message-ID: <20200619150556.GW700896@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20200619020602.118306-1-david@gibson.dropbear.id.au> <20200619020602.118306-10-david@gibson.dropbear.id.au> <20200619101245.GC700896@redhat.com> <20200619144541.GM17085@umbus.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200619144541.GM17085@umbus.fritz.box> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Sat, Jun 20, 2020 at 12:45:41AM +1000, David Gibson wrote: > On Fri, Jun 19, 2020 at 11:12:45AM +0100, Daniel P. Berrangé wrote: > > On Fri, Jun 19, 2020 at 12:06:02PM +1000, David Gibson wrote: > > > The default behaviour for virtio devices is not to use the platforms normal > > > DMA paths, but instead to use the fact that it's running in a hypervisor > > > to directly access guest memory. That doesn't work if the guest's memory > > > is protected from hypervisor access, such as with AMD's SEV or POWER's PEF. > > > > > > So, if a host trust limitation mechanism is enabled, then apply the > > > iommu_platform=on option so it will go through normal DMA mechanisms. > > > Those will presumably have some way of marking memory as shared with the > > > hypervisor or hardware so that DMA will work. > > > > > > Signed-off-by: David Gibson > > > --- > > > hw/core/machine.c | 11 +++++++++++ > > > 1 file changed, 11 insertions(+) > > > > > > diff --git a/hw/core/machine.c b/hw/core/machine.c > > > index a71792bc16..8dfc1bb3f8 100644 > > > --- a/hw/core/machine.c > > > +++ b/hw/core/machine.c > > > @@ -28,6 +28,8 @@ > > > #include "hw/mem/nvdimm.h" > > > #include "migration/vmstate.h" > > > #include "exec/host-trust-limitation.h" > > > +#include "hw/virtio/virtio.h" > > > +#include "hw/virtio/virtio-pci.h" > > > > > > GlobalProperty hw_compat_5_0[] = { > > > { "virtio-balloon-device", "page-poison", "false" }, > > > @@ -1165,6 +1167,15 @@ void machine_run_board_init(MachineState *machine) > > > * areas. > > > */ > > > machine_set_mem_merge(OBJECT(machine), false, &error_abort); > > > + > > > + /* > > > + * Virtio devices can't count on directly accessing guest > > > + * memory, so they need iommu_platform=on to use normal DMA > > > + * mechanisms. That requires disabling legacy virtio support > > > + * for virtio pci devices > > > + */ > > > + object_register_sugar_prop(TYPE_VIRTIO_PCI, "disable-legacy", "on"); > > > + object_register_sugar_prop(TYPE_VIRTIO_DEVICE, "iommu_platform", "on"); > > > } > > > > Silently changing the user's request configuration like this > > It doesn't, though. register_sugar_prop() effectively registers a > default, so if the user has explicitly specified something, that will > take precedence. Don't assume that the user has set "disable-legacy=off". People who want to have a transtional device are almost certainly pasing "-device virtio-blk-pci", because historical behaviour is that this is sufficient to give you a transitional device. Changing the default of disable-legacy=on has not honoured the users' requested config. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|