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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 085CAC433F5 for ; Fri, 28 Jan 2022 12:24:19 +0000 (UTC) Received: from localhost ([::1]:47924 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nDQIb-0005Rn-Sm for qemu-devel@archiver.kernel.org; Fri, 28 Jan 2022 07:24:17 -0500 Received: from eggs.gnu.org ([209.51.188.92]:32922) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nDPne-0005JH-67 for qemu-devel@nongnu.org; Fri, 28 Jan 2022 06:52:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:33406) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nDPna-0003fs-4H for qemu-devel@nongnu.org; Fri, 28 Jan 2022 06:52:16 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643370733; h=from:from: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=w3UIWxZKYaAiom5/G0Lf9mDViqGTootNDmyibErEoK8=; b=ej/d0yFmJhBTHnTCRhAB2tMNPtiN6HaIpiwjPBVzOE+waip0cADwouhJrmV9rzxj4pNdx4 UVs7kmafO8RT7eFznE8YUHY7olwbdmeE6a/cdR1FMvuy4P4e3qSpNPzly/cERzljDTtU+7 m6LaAhnF8PRWjxF232+eSzrfN3Ay7mU= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-532-2VQMVjPCPiuWMRusqote1g-1; Fri, 28 Jan 2022 06:52:10 -0500 X-MC-Unique: 2VQMVjPCPiuWMRusqote1g-1 Received: by mail-wr1-f71.google.com with SMTP id z1-20020adfbbc1000000b001df54394cebso1329602wrg.20 for ; Fri, 28 Jan 2022 03:52:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=w3UIWxZKYaAiom5/G0Lf9mDViqGTootNDmyibErEoK8=; b=sFk1n59Nd+XrzCSx4cwCJwfwu0CxvKOOgGTWgT0nYLI06TR/oMCk7oLlIMxopYIv79 1ZE0VirHR8ALvuvAwZiRqRqZcbwH2GCIoH8iTMoxNYu8P8Ova0HA0eggFJ/iKQCHwdj4 FEJ22y0nXKo3r3hJXlLg/57ByRvH5eim5G+rD/Wxq+FmocVdFAWijSNbcmMCNZiIBPm/ eOEoq7oGR5Li76Hi3mF/mtKR+tK+cjPoSev3g0SWdSnOGqNcEKH4lscyqYyQkNAC2PXW aBWugiSF0HtYvwMrBKKoftVBEQqz+Ktc3kxMgi5hLuTfIa5VcYhxB4diDUf9mUtbx55R PkgA== X-Gm-Message-State: AOAM533LfHloBJRvoD+v5JXDPN1iPkWxhJzEEguoBQ1ZSUh6cEv3jzcq OuPyYYzckIJMa7jLlbJX5iyBlv6iUxuWTRKjXm/Bw8Od25Mm1VmObxn/PkvVaF+SkTgFguqa7HO zYGgq9ncQUCVd/aI= X-Received: by 2002:a1c:f719:: with SMTP id v25mr7377416wmh.76.1643370729460; Fri, 28 Jan 2022 03:52:09 -0800 (PST) X-Google-Smtp-Source: ABdhPJxxvyCo1Cgm8ZoThoFwIt6L13GWoSaHHJSPnekDGjmtSlJwMogT6kvvK1YCptB7YXcxPjF3Vg== X-Received: by 2002:a1c:f719:: with SMTP id v25mr7377381wmh.76.1643370729066; Fri, 28 Jan 2022 03:52:09 -0800 (PST) Received: from redhat.com ([2.55.144.199]) by smtp.gmail.com with ESMTPSA id o8sm1662961wmc.46.2022.01.28.03.52.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Jan 2022 03:52:08 -0800 (PST) Date: Fri, 28 Jan 2022 06:52:04 -0500 From: "Michael S. Tsirkin" To: Daniel Henrique Barboza Subject: Re: [PATCH v2 1/1] virtio: fix the condition for iommu_platform not supported Message-ID: <20220128064621-mutt-send-email-mst@kernel.org> References: <20220117120238.2519239-1-pasic@linux.ibm.com> <20220125112112.44957075.pasic@linux.ibm.com> <20220127142800.11d8f1be.pasic@linux.ibm.com> <20220128032911.440323f1.pasic@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Brijesh Singh , Daniel Henrique Barboza , Cornelia Huck , qemu-devel@nongnu.org, qemu-stable@nongnu.org, Halil Pasic , Jakob Naucke Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jan 28, 2022 at 08:02:39AM -0300, Daniel Henrique Barboza wrote: > > > On 1/27/22 23:29, Halil Pasic wrote: > > On Thu, 27 Jan 2022 18:34:23 -0300 > > Daniel Henrique Barboza wrote: > > > > > On 1/27/22 10:28, Halil Pasic wrote: > > > > ping^2 > > > > > > > > Also adding Brijesh and Daniel, as I believe you guys should be > > > > interested in this, and I'm yet to receive review. > > > > > > > > @Brijesh, Daniel: Can you confirm that AMD (SEV) and Power are affected > > > > too, and that the fix works for your platforms as well? > > > > > > I failed to find a host that has Power secure execution support. I'll keep looking. > > > > > > > > > Meanwhile I have to mention that this patch re-introduced the problem that Kevin's > > > commit fixed. > > [...] > > > > > > > I made a little experiment with upstream and reverting Kevin's patch and the result is > > > the same, meaning that this is the original bug [1] Kevin fixed back then. Note that [1] > > > was reported on x86, meaning that this particular issue seems to be arch agnostic. > > > > We don't have this problem on s390, so it ain't entirely arch agnostic. > > It is arch agnostic in a way that it relies on iommu_platform support being true to this > specific device (vhost-user-fs-pci) instead of some particularity of the machine. But it is specific to VMs with an IOMMU or other ways to restrict access such as cgs, right? Without a vIOMMU or cgs in the VM the ACCESS_PLATFORM flag is a nop for the guest, it doesn't affect anything except slowing things down somewhat, right? > > > > > > > > > > > My point here is that your patch fixes the situation for s390x, and Brijesh already chimed > > > in claiming that it fixed for AMD SEV, but it reintroduced a bug. I believe you should > > > include this test case with vhost-user in your testing to figure out a way to fix what > > > is needed without adding this particular regression. > > > > Can you help me with this? IMHO the big problem is that iommu_platform > > is used for two distinct things. I've described that in the commit > > message. > > > > We may be able to differentiate between the two using ->dma_as, but for > > that it needs to be set up correctly: whenever you require translation > > it should be something different than address_space_memory. The question > > is why do you require translation but don't have your ->dma_as set up > > properly? It can be a guest thing, i.e. guest just assumes it has to do > > bus addresses, while it actually does not have to, or we indeed do have > > an IOMMU which polices the devices access to the guest memory, but for > > some strange reason we failed to set up ->dma_as to reflect that. > > > I have 2 suggestions. First is to separate how we interpret iommu_platform. I find it > hard to do this properly without creating a new flag/command line option. We do want to switch to call it access_platform at some point anyway. When we do, we can make it only mean the guest flag. > > My second suggestion is, well .... I think it's proved that s390x-PV and AMD SEV are > being impacted (and probably Power secure guests as well), so why not check for > confidential guest support to skip that check entirely? Something like this patch: > > diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c > index d23db98c56..4305fdd1b7 100644 > --- a/hw/virtio/virtio-bus.c > +++ b/hw/virtio/virtio-bus.c > @@ -29,6 +29,7 @@ > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio.h" > #include "exec/address-spaces.h" > +#include "hw/boards.h" > /* #define DEBUG_VIRTIO_BUS */ > @@ -42,6 +43,7 @@ do { printf("virtio_bus: " fmt , ## __VA_ARGS__); } while (0) > /* A VirtIODevice is being plugged */ > void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > { > + MachineState *machine = MACHINE(qdev_get_machine()); > DeviceState *qdev = DEVICE(vdev); > BusState *qbus = BUS(qdev_get_parent_bus(qdev)); > VirtioBusState *bus = VIRTIO_BUS(qbus); > @@ -69,7 +71,18 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > return; > } > - if (has_iommu && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > + /* > + * Confidential guest technologies such as AMD SEV and s390x-PV relies > + * on device/hypervisor offering _F_ACCESS_PLATFORM so the guest grants > + * access to the portions of memory the device needs to see. For these > + * guests, _F_ACCESS_PLATFORM is about the restricted access to memory, > + * but not about infering whether iommu_platform is supported in the > + * device. > + * > + * Skip this check for these guests by checking machine->cgs. > + */ > + if (!machine->cgs && has_iommu && > + !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > error_setg(errp, "iommu_platform=true is not supported by the device"); > return; > } > -- > 2.34.1 In fact I proposed setting _F_ACCESS_PLATFORM automatically in the past, > > This will not break anything for non-secure guests and, granted that machine->cgs is already > set at this point, this will fix the problem for s390x-PV and AMD SEV. And we won't have to > dive deep into a virtio-bus feature negotiation saga because of something that can be easily > handled for machine->cgs guests only. > > If this patch works for you and Brijesh I believe this is a good option. > > > > Thanks, > > > Daniel > > > > > > > @Michael: what is your opinion? > > > > > > > > > > > In fact, I have a feeling that this is not the first time this kind of situation is discussed > > > around here. This reminds me of [2] and a discussion about the order virtiofs features > > > are negotiated versus when/how QEMU inits the devices. > > > > > > > > > > > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=1935019 > > > [2] https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg05644.html > > > > > > > > > Thanks, > > > > > > > > > Daniel > > > > > > > > > > > > > > Regards, > > > > Halil > > > > > > > > On Tue, 25 Jan 2022 11:21:12 +0100 > > > > Halil Pasic wrote: > > > > > ping > > > > > > > > > > On Mon, 17 Jan 2022 13:02:38 +0100 > > > > > Halil Pasic wrote: > > > > > > The commit 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but > > > > > > unsupported") claims to fail the device hotplug when iommu_platform > > > > > > is requested, but not supported by the (vhost) device. On the first > > > > > > glance the condition for detecting that situation looks perfect, but > > > > > > because a certain peculiarity of virtio_platform it ain't. > > > > > > > > > > > > In fact the aforementioned commit introduces a regression. It breaks > > > > > > virtio-fs support for Secure Execution, and most likely also for AMD SEV > > > > > > or any other confidential guest scenario that relies encrypted guest > > > > > > memory. The same also applies to any other vhost device that does not > > > > > > support _F_ACCESS_PLATFORM. > > > > > > > > > > > > The peculiarity is that iommu_platform and _F_ACCESS_PLATFORM collates > > > > > > "device can not access all of the guest RAM" and "iova != gpa, thus > > > > > > device needs to translate iova". > > > > > > > > > > > > Confidential guest technologies currently rely on the device/hypervisor > > > > > > offering _F_ACCESS_PLATFORM, so that, after the feature has been > > > > > > negotiated, the guest grants access to the portions of memory the > > > > > > device needs to see. So in for confidential guests, generally, > > > > > > _F_ACCESS_PLATFORM is about the restricted access to memory, but not > > > > > > about the addresses used being something else than guest physical > > > > > > addresses. > > > > > > > > > > > > This is the very reason for which commit f7ef7e6e3b ("vhost: correctly > > > > > > turn on VIRTIO_F_IOMMU_PLATFORM") for, which fences _F_ACCESS_PLATFORM > > > > > > form the vhost device that does not need it, because on the vhost > > > > > > interface it only means "I/O address translation is needed". > > > > > > > > > > > > This patch takes inspiration from f7ef7e6e3b ("vhost: correctly turn on > > > > > > VIRTIO_F_IOMMU_PLATFORM"), and uses the same condition for detecting the > > > > > > situation when _F_ACCESS_PLATFORM is requested, but no I/O translation > > > > > > by the device, and thus no device capability is needed. In this > > > > > > situation claiming that the device does not support iommu_plattform=on > > > > > > is counter-productive. So let us stop doing that! > > > > > > > > > > > > Signed-off-by: Halil Pasic > > > > > > Reported-by: Jakob Naucke > > > > > > Fixes: 04ceb61a40 ("virtio: Fail if iommu_platform is requested, but > > > > > > unsupported") > > > > > > Cc: Kevin Wolf > > > > > > Cc: qemu-stable@nongnu.org > > > > > > > > > > > > --- > > > > > > > > > > > > v1->v2: > > > > > > * Commit message tweaks. Most notably fixed commit SHA (Michael) > > > > > > > > > > > > --- > > > > > > hw/virtio/virtio-bus.c | 11 ++++++----- > > > > > > 1 file changed, 6 insertions(+), 5 deletions(-) > > > > > > > > > > > > diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c > > > > > > index d23db98c56..c1578f3de2 100644 > > > > > > --- a/hw/virtio/virtio-bus.c > > > > > > +++ b/hw/virtio/virtio-bus.c > > > > > > @@ -69,11 +69,6 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > > > > > > return; > > > > > > } > > > > > > - if (has_iommu && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > > > > > > - error_setg(errp, "iommu_platform=true is not supported by the device"); > > > > > > - return; > > > > > > - } > > > > > > - > > > > > > if (klass->device_plugged != NULL) { > > > > > > klass->device_plugged(qbus->parent, &local_err); > > > > > > } > > > > > > @@ -88,6 +83,12 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp) > > > > > > } else { > > > > > > vdev->dma_as = &address_space_memory; > > > > > > } > > > > > > + > > > > > > + if (has_iommu && vdev->dma_as != &address_space_memory > > > > > > + && !virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) { > > > > > > + error_setg(errp, "iommu_platform=true is not supported by the device"); > > > > > > + return; > > > > > > + } > > > > > > } > > > > > > /* Reset the virtio_bus */ > > > > > > > > > > > > base-commit: 6621441db50d5bae7e34dbd04bf3c57a27a71b32 > > > > > > > > >