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[209.132.180.67]) by mx.google.com with ESMTP id v18si609136oth.1.2020.03.05.19.37.05; Thu, 05 Mar 2020 19:37:17 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=Fw5W1HzN; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726957AbgCFDfk (ORCPT + 99 others); Thu, 5 Mar 2020 22:35:40 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:25273 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726565AbgCFDfk (ORCPT ); Thu, 5 Mar 2020 22:35:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583465738; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6EZalpkWJawotNixfanTTs27PQUK9gnQWERCmK6d7yk=; b=Fw5W1HzN2o8gDhy2Y0Ihh79B9toV7AsMHty/jRkqr3U31YmhR5be/PE0hx7L5bPM3A8G0H 7qeRtocpbhPlxpkrjWfkvv1fuw8i8iTSvpxLkYxAdPgqJAYU1mu0YenmAOV8REQmCz3p1V Sm3tCkEOxLQayYUgK+BMljPvCjMNvMk= 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-224-v5JIgj87P1ekz7L5n2ZW2A-1; Thu, 05 Mar 2020 22:35:33 -0500 X-MC-Unique: v5JIgj87P1ekz7L5n2ZW2A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7AD15800D53; Fri, 6 Mar 2020 03:35:31 +0000 (UTC) Received: from [10.72.13.242] (ovpn-13-242.pek2.redhat.com [10.72.13.242]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8576360BE0; Fri, 6 Mar 2020 03:35:23 +0000 (UTC) Subject: Re: [PATCH v2 0/7] vfio/pci: SR-IOV support To: Alex Williamson Cc: "Tian, Kevin" , "kvm@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "dev@dpdk.org" , "mtosatti@redhat.com" , "thomas@monjalon.net" , "bluca@debian.org" , "jerinjacobk@gmail.com" , "Richardson, Bruce" , "cohuck@redhat.com" References: <158213716959.17090.8399427017403507114.stgit@gimli.home> <20200305101406.02703e2a@w520.home> From: Jason Wang Message-ID: <3e8db1d0-8afc-f1e9-e857-aead4717fa11@redhat.com> Date: Fri, 6 Mar 2020 11:35:21 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200305101406.02703e2a@w520.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/6 =E4=B8=8A=E5=8D=881:14, Alex Williamson wrote: > On Tue, 25 Feb 2020 14:09:07 +0800 > Jason Wang wrote: > >> On 2020/2/25 =E4=B8=8A=E5=8D=8810:33, Tian, Kevin wrote: >>>> From: Alex Williamson >>>> Sent: Thursday, February 20, 2020 2:54 AM >>>> >>>> Changes since v1 are primarily to patch 3/7 where the commit log is >>>> rewritten, along with option parsing and failure logging based on >>>> upstream discussions. The primary user visible difference is that >>>> option parsing is now much more strict. If a vf_token option is >>>> provided that cannot be used, we generate an error. As a result of >>>> this, opening a PF with a vf_token option will serve as a mechanism = of >>>> setting the vf_token. This seems like a more user friendly API than >>>> the alternative of sometimes requiring the option (VFs in use) and >>>> sometimes rejecting it, and upholds our desire that the option is >>>> always either used or rejected. >>>> >>>> This also means that the VFIO_DEVICE_FEATURE ioctl is not the only >>>> means of setting the VF token, which might call into question whethe= r >>>> we absolutely need this new ioctl. Currently I'm keeping it because= I >>>> can imagine use cases, for example if a hypervisor were to support >>>> SR-IOV, the PF device might be opened without consideration for a VF >>>> token and we'd require the hypservisor to close and re-open the PF i= n >>>> order to set a known VF token, which is impractical. >>>> >>>> Series overview (same as provided with v1): >>> Thanks for doing this! >>> =20 >>>> The synopsis of this series is that we have an ongoing desire to dri= ve >>>> PCIe SR-IOV PFs from userspace with VFIO. There's an immediate need >>>> for this with DPDK drivers and potentially interesting future use >>> Can you provide a link to the DPDK discussion? >>> =20 >>>> cases in virtualization. We've been reluctant to add this support >>>> previously due to the dependency and trust relationship between the >>>> VF device and PF driver. Minimally the PF driver can induce a denia= l >>>> of service to the VF, but depending on the specific implementation, >>>> the PF driver might also be responsible for moving data between VFs >>>> or have direct access to the state of the VF, including data or stat= e >>>> otherwise private to the VF or VF driver. >>> Just a loud thinking. While the motivation of VF token sounds reasona= ble >>> to me, I'm curious why the same concern is not raised in other usages= . >>> For example, there is no such design in virtio framework, where the >>> virtio device could also be restarted, putting in separate process (v= host-user), >>> and even in separate VM (virtio-vhost-user), etc. >> >> AFAIK, the restart could only be triggered by either VM or qemu. But >> yes, the datapath could be offloaded. >> >> But I'm not sure introducing another dedicated mechanism is better tha= n >> using the exist generic POSIX mechanism to make sure the connection >> (AF_UINX) is secure. >> >> >>> Of course the para- >>> virtualized attribute of virtio implies some degree of trust, but as = you >>> mentioned many SR-IOV implementations support VF->PF communication >>> which also implies some level of trust. It's perfectly fine if VFIO j= ust tries >>> to do better than other sub-systems, but knowing how other people >>> tackle the similar problem may make the whole picture clearer. =F0=9F= =98=8A >>> >>> +Jason. >> >> I'm not quite sure e.g allowing userspace PF driver with kernel VF >> driver would not break the assumption of kernel security model. At lea= st >> we should forbid a unprivileged PF driver running in userspace. > It might be useful to have your opinion on this series, because that's > exactly what we're trying to do here. Various environments, DPDK > specifically, want a userspace PF driver. This series takes steps to > mitigate the risk of having such a driver, such as requiring this VF > token interface to extend the VFIO interface and validate participation > around a PF that is not considered trusted by the kernel. I may miss something. But what happens if: - PF driver is running by unprivileged user - PF is programmed to send translated DMA request - Then unprivileged user can mangle the kernel data > We also set > a driver_override to try to make sure no host kernel driver can > automatically bind to a VF of a user owned PF, only vfio-pci, but we > don't prevent the admin from creating configurations where the VFs are > used by other host kernel drivers. > > I think the question Kevin is inquiring about is whether virtio devices > are susceptible to the type of collaborative, shared key environment > we're creating here. For example, can a VM or qemu have access to > reset a virtio device in a way that could affect other devices, ex. FLR > on a PF that could interfere with VF operation. Thanks, Right, but I'm not sure it can be done only via virtio or need support=20 from transport (e.g PCI). Thanks > > Alex >