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 710C1C433EF for ; Fri, 28 Jan 2022 09:50:31 +0000 (UTC) Received: from localhost ([::1]:50020 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nDNtl-0001iF-SW for qemu-devel@archiver.kernel.org; Fri, 28 Jan 2022 04:50:29 -0500 Received: from eggs.gnu.org ([209.51.188.92]:36706) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nDNrg-0008PS-4r for qemu-devel@nongnu.org; Fri, 28 Jan 2022 04:48:21 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:49679) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nDNrb-0001vd-RI for qemu-devel@nongnu.org; Fri, 28 Jan 2022 04:48:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643363294; 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=sz/5lubMAr5aTwlU+gba/YKMU/b6wnqVD6BrwYOGgIo=; b=EI9uqkb5iU4IAG0RmkwkJF9oxEQ75GqkcCr0zDjoA32EQNmp2oeUnUOQxm9cRFkHjWHgJg D4034T+SCUakyCXUu5M1Fp6itFHygCzerEAQ8IRz1QYfJqTvXzNgki3OAyBsas6FQONB5/ At/TYOVtHHOh3LwQfIaiw/z23i840tg= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-12-KLHR4g0QMa-rxxKEq20_bg-1; Fri, 28 Jan 2022 04:48:11 -0500 X-MC-Unique: KLHR4g0QMa-rxxKEq20_bg-1 Received: by mail-wr1-f69.google.com with SMTP id c10-20020adfa30a000000b001d79c73b64bso2069431wrb.1 for ; Fri, 28 Jan 2022 01:48:11 -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=sz/5lubMAr5aTwlU+gba/YKMU/b6wnqVD6BrwYOGgIo=; b=rfWHqpCybg+dKenpStbgjL+xp98hQIBnf8GNvsX/7HwO4lPCldHlTJIaiBuvarsHyL eLfHtdWofMsEuiph7O/5Oi1c/wt4AmJ4i/qnBTN3xWoT5b18qBFCWelURvOyaf1+4HO6 aCSPLdpQ58dro4J4BFL9BeU1Ki6HhqLSIAgSmpCGZFHAkX4FBN+/H11oI4sfuVDhGAZM 9yX3QuSlc25FqMV79jZoEgVztr1x436WIAVBbQei8mWLr5Q3yIqFFevhpIknAX1LNc3x a4nJvqZSmBJAWLDQBZwWbVrfLY93zssDyY4FvI+jdIwHj/sjE5cW98ia2PVgwMIujYkC 765g== X-Gm-Message-State: AOAM532A0mnWzpObBBAzYST/gKsQ8Q5ETq7/Cv4iaUDndYc/s9bko8LZ FBVuKa11yz82e5hwpbBZibc9LCQMb/vhL7+DGjNjZKiWBFEV8ZwBKV+g3c3h1CzP4A5+miYR9MP NPky6FEWe6Np/Lro= X-Received: by 2002:a7b:c20d:: with SMTP id x13mr14863896wmi.47.1643363290330; Fri, 28 Jan 2022 01:48:10 -0800 (PST) X-Google-Smtp-Source: ABdhPJwFH6hSafPpeK7ux2CQUGAEpfOEt+GdZ0795k1xKJAyR9WZ3O8LqJXZuS7ECUXclaEtrx3dnQ== X-Received: by 2002:a7b:c20d:: with SMTP id x13mr14863861wmi.47.1643363289885; Fri, 28 Jan 2022 01:48:09 -0800 (PST) Received: from redhat.com ([2.55.144.199]) by smtp.gmail.com with ESMTPSA id v124sm1514154wme.30.2022.01.28.01.48.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Jan 2022 01:48:09 -0800 (PST) Date: Fri, 28 Jan 2022 04:48:05 -0500 From: "Michael S. Tsirkin" To: Halil Pasic Subject: Re: [PATCH v2 1/1] virtio: fix the condition for iommu_platform not supported Message-ID: <20220128044643-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: <20220128032911.440323f1.pasic@linux.ibm.com> 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 , Cornelia Huck , Brijesh Singh , Daniel Henrique Barboza , Daniel Henrique Barboza , qemu-devel@nongnu.org, qemu-stable@nongnu.org, Jakob Naucke Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jan 28, 2022 at 03:29:11AM +0100, 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. > > > > > > With current upstream, if you start a regular guest with the following command line: > > > > qemu-system-ppc64 (....) > > -chardev socket,id=char0,path=/tmp/vhostqemu > > -device vhost-user-fs-pci,chardev=char0,tag=myfs,iommu_platform=on > > > > i.e. a guest with a vhost-user-fs-pci device that claims to have iommu support, > > but it doesn't, this is the error message: > > > > > > qemu-system-ppc64: -device vhost-user-fs-pci,chardev=char0,tag=myfs,iommu_platform=on: iommu_platform=true is not supported by the device > > > > > > With this patch, that command line above starts the guest. > > virtiofsd fails during boot: > > > > sudo ~/qemu/build/tools/virtiofsd/virtiofsd --socket-path=/tmp/vhostqemu -o source=~/linux-L1 > > [sudo] password for danielhb: > > virtio_session_mount: Waiting for vhost-user socket connection... > > virtio_session_mount: Received vhost-user socket connection > > virtio_loop: Entry > > fv_panic: libvhost-user: Invalid vring_addr message > > > > > > And inside the guest, if you attempt to mount and use the virtiofs filesystem, the guest > > hangs: > > > > [root@localhost ~]# mount -t virtiofs myfs /mnt > > [root@localhost ~]# cd /mnt > > > > (hangs) > > > > Exiting QEMU throws several vhost related errors: > > > > > > QEMU 6.2.50 monitor - type 'help' for more information > > (qemu) quit > > qemu-system-ppc64: Failed to set msg fds. > > qemu-system-ppc64: vhost VQ 0 ring restore failed: -22: Invalid argument (22) > > qemu-system-ppc64: Failed to set msg fds. > > qemu-system-ppc64: vhost VQ 1 ring restore failed: -22: Invalid argument (22) > > qemu-system-ppc64: Failed to set msg fds. > > qemu-system-ppc64: vhost_set_vring_call failed: Invalid argument (22) > > qemu-system-ppc64: Failed to set msg fds. > > qemu-system-ppc64: vhost_set_vring_call failed: Invalid argument (22) > > > > > > > Does your VM have an IOMMU and does your guest see it? If yes does > vdev->dma_as != &address_space_memory hold for your virtio device? If no why not? > > My understanding is that your guest wants to do translated addresses, > because it sees the ACCESS_PLATFORM feature, and probably thinks that > your device is indeed behind an IOMMU, from what I assume, at least it > sees that there is an IOMMU. But then I would expect your virtio device > to have its vdev->dma_as set to something different than > &address_space_memory. Conversely if your dma address space is > address_space_memory, then you don't need address translation because > your dma addresses are the same as your guest physical addresses. > > > > > 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. > > > > > > > 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. > > @Michael: what is your opinion? Right, I am puzzled too. > > > > > > 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 > > >> > > > > > > > >