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=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 024D4C433DF for ; Fri, 19 Jun 2020 10:13:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE4152073E for ; Fri, 19 Jun 2020 10:13:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="S5mY+iIa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732225AbgFSKNG (ORCPT ); Fri, 19 Jun 2020 06:13:06 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:52775 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729195AbgFSKNF (ORCPT ); Fri, 19 Jun 2020 06:13:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592561584; 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:in-reply-to:in-reply-to: references:references; bh=9TgD00zswi6kpjxkdsGTBBsyLXcp4Zg0SPr+uYeXtzY=; b=S5mY+iIaXu43BWW4WtEWto9PA+8uDxcWVkjJ+wJZgqaku6qY1Am4uybsE4IstvrAF9B6fj Gwqdc03OWAlT8mZMiHwXXxw/qXPgyTG1vmtCVNjVYfMkPgI1+6griZvKtffD+QnGCmXuy0 k5GuwSN/ARK2Q5uCXUg1WhsriSPLQ4g= 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-493-Vl5k1qLxM66UqSBccjOoCw-1; Fri, 19 Jun 2020 06:13:00 -0400 X-MC-Unique: Vl5k1qLxM66UqSBccjOoCw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0A448800053; Fri, 19 Jun 2020 10:12:59 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8F75F71661; Fri, 19 Jun 2020 10:12:48 +0000 (UTC) Date: Fri, 19 Jun 2020 11:12:45 +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: <20200619101245.GC700896@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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200619020602.118306-10-david@gibson.dropbear.id.au> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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 is a bad idea. The "disable-legacy" option in particular is undesirable as that switches the device to virtio-1.0 only mode, which exposes a different PCI ID to the guest. If some options are incompatible with encryption, then we should raise a fatal error at startup, so applications/admins are aware that their requested config is broken. 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 :|