From: Stefan Hajnoczi <stefanha@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
"Jonathan Corbet" <corbet@lwn.net>,
kvm@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
netdev@vger.kernel.org, "Randy Dunlap" <rdunlap@infradead.org>,
"Matthew Wilcox" <willy@infradead.org>,
virtualization@lists.linux-foundation.org,
"Christoph Hellwig" <hch@infradead.org>,
"Yongji Xie" <xieyongji@bytedance.com>,
"Christian Brauner" <christian.brauner@canonical.com>,
bcrl@kvack.org, viro@zeniv.linux.org.uk,
linux-fsdevel@vger.kernel.org,
"Dan Carpenter" <dan.carpenter@oracle.com>,
"Mika Penttilä" <mika.penttila@nextfour.com>
Subject: Re: [PATCH v6 10/10] Documentation: Add documentation for VDUSE
Date: Thu, 15 Apr 2021 15:38:26 +0100 [thread overview]
Message-ID: <YHhP4i+yXgA2KkVJ@stefanha-x1.localdomain> (raw)
In-Reply-To: <80b31814-9e41-3153-7efb-c0c2fab44feb@redhat.com>
[-- Attachment #1.1: Type: text/plain, Size: 5389 bytes --]
On Thu, Apr 15, 2021 at 04:36:35PM +0800, Jason Wang wrote:
>
> 在 2021/4/15 下午3:19, Stefan Hajnoczi 写道:
> > On Thu, Apr 15, 2021 at 01:38:37PM +0800, Yongji Xie wrote:
> > > On Wed, Apr 14, 2021 at 10:15 PM Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > > > On Wed, Mar 31, 2021 at 04:05:19PM +0800, Xie Yongji wrote:
> > > > > VDUSE (vDPA Device in Userspace) is a framework to support
> > > > > implementing software-emulated vDPA devices in userspace. This
> > > > > document is intended to clarify the VDUSE design and usage.
> > > > >
> > > > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > > > ---
> > > > > Documentation/userspace-api/index.rst | 1 +
> > > > > Documentation/userspace-api/vduse.rst | 212 ++++++++++++++++++++++++++++++++++
> > > > > 2 files changed, 213 insertions(+)
> > > > > create mode 100644 Documentation/userspace-api/vduse.rst
> > > > Just looking over the documentation briefly (I haven't studied the code
> > > > yet)...
> > > >
> > > Thank you!
> > >
> > > > > +How VDUSE works
> > > > > +------------
> > > > > +Each userspace vDPA device is created by the VDUSE_CREATE_DEV ioctl on
> > > > > +the character device (/dev/vduse/control). Then a device file with the
> > > > > +specified name (/dev/vduse/$NAME) will appear, which can be used to
> > > > > +implement the userspace vDPA device's control path and data path.
> > > > These steps are taken after sending the VDPA_CMD_DEV_NEW netlink
> > > > message? (Please consider reordering the documentation to make it clear
> > > > what the sequence of steps are.)
> > > >
> > > No, VDUSE devices should be created before sending the
> > > VDPA_CMD_DEV_NEW netlink messages which might produce I/Os to VDUSE.
> > I see. Please include an overview of the steps before going into detail.
> > Something like:
> >
> > VDUSE devices are started as follows:
> >
> > 1. Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on
> > /dev/vduse/control.
> >
> > 2. Begin processing VDUSE messages from /dev/vduse/$NAME. The first
> > messages will arrive while attaching the VDUSE instance to vDPA.
> >
> > 3. Send the VDPA_CMD_DEV_NEW netlink message to attach the VDUSE
> > instance to vDPA.
> >
> > VDUSE devices are stopped as follows:
> >
> > ...
> >
> > > > > + static int netlink_add_vduse(const char *name, int device_id)
> > > > > + {
> > > > > + struct nl_sock *nlsock;
> > > > > + struct nl_msg *msg;
> > > > > + int famid;
> > > > > +
> > > > > + nlsock = nl_socket_alloc();
> > > > > + if (!nlsock)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + if (genl_connect(nlsock))
> > > > > + goto free_sock;
> > > > > +
> > > > > + famid = genl_ctrl_resolve(nlsock, VDPA_GENL_NAME);
> > > > > + if (famid < 0)
> > > > > + goto close_sock;
> > > > > +
> > > > > + msg = nlmsg_alloc();
> > > > > + if (!msg)
> > > > > + goto close_sock;
> > > > > +
> > > > > + if (!genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, famid, 0, 0,
> > > > > + VDPA_CMD_DEV_NEW, 0))
> > > > > + goto nla_put_failure;
> > > > > +
> > > > > + NLA_PUT_STRING(msg, VDPA_ATTR_DEV_NAME, name);
> > > > > + NLA_PUT_STRING(msg, VDPA_ATTR_MGMTDEV_DEV_NAME, "vduse");
> > > > > + NLA_PUT_U32(msg, VDPA_ATTR_DEV_ID, device_id);
> > > > What are the permission/capability requirements for VDUSE?
> > > >
> > > Now I think we need privileged permission (root user). Because
> > > userspace daemon is able to access avail vring, used vring, descriptor
> > > table in kernel driver directly.
> > Please state this explicitly at the start of the document. Existing
> > interfaces like FUSE are designed to avoid trusting userspace.
>
>
> There're some subtle difference here. VDUSE present a device to kernel which
> means IOMMU is probably the only thing to prevent a malicous device.
>
>
> > Therefore
> > people might think the same is the case here. It's critical that people
> > are aware of this before deploying VDUSE with virtio-vdpa.
> >
> > We should probably pause here and think about whether it's possible to
> > avoid trusting userspace. Even if it takes some effort and costs some
> > performance it would probably be worthwhile.
>
>
> Since the bounce buffer is used the only attack surface is the coherent
> area, if we want to enforce stronger isolation we need to use shadow
> virtqueue (which is proposed in earlier version by me) in this case. But I'm
> not sure it's worth to do that.
The security situation needs to be clear before merging this feature.
I think the IOMMU and vring can be made secure. What is more concerning
is the kernel code that runs on top: VIRTIO device drivers, network
stack, file systems, etc. They trust devices to an extent.
Since virtio-vdpa is a big reason for doing VDUSE in the first place I
don't think it makes sense to disable virtio-vdpa with VDUSE. A solution
is needed.
I'm going to be offline for a week and don't want to be a bottleneck.
I'll catch up when I'm back.
Stefan
[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
[-- Attachment #2: Type: text/plain, Size: 183 bytes --]
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-04-15 14:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210331080519.172-1-xieyongji@bytedance.com>
[not found] ` <20210331080519.172-2-xieyongji@bytedance.com>
[not found] ` <20210331091545.lr572rwpyvrnji3w@wittgenstein>
2021-03-31 9:26 ` [PATCH v6 01/10] file: Export receive_fd() to modules Dan Carpenter
[not found] ` <20210331080519.172-8-xieyongji@bytedance.com>
2021-04-08 2:36 ` [PATCH v6 07/10] vdpa: Support transferring virtual addressing during DMA mapping Jason Wang
[not found] ` <20210331080519.172-9-xieyongji@bytedance.com>
2021-04-08 3:25 ` [PATCH v6 08/10] vduse: Implement an MMU-based IOMMU driver Jason Wang
[not found] ` <20210331080519.172-10-xieyongji@bytedance.com>
2021-04-08 6:57 ` [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace Jason Wang
[not found] ` <CACycT3v_KFQXoxRbEj8c0Ve6iKn9RbibtBDgBFs=rf0ZOmTBBQ@mail.gmail.com>
2021-04-09 5:36 ` Jason Wang
[not found] ` <CACycT3vwATp4+Ao0fjuyeeLQN+xHH=dXF+JUyuitkn4k8hELnA@mail.gmail.com>
2021-04-12 7:16 ` Jason Wang
[not found] ` <CACycT3vxO21Yt6+px2c2Q8DONNUNehdo2Vez_RKQCKe76CM2TA@mail.gmail.com>
2021-04-12 9:37 ` Jason Wang
[not found] ` <CACycT3vbDhUKM0OX-zo02go09gh2+EEdyZ_YQuz8PXzo3EngXw@mail.gmail.com>
2021-04-13 3:35 ` Jason Wang
[not found] ` <CACycT3tHxtfgQhQgv0VyF_U523qASEv1Ydc4XuX43MFRzGVbfw@mail.gmail.com>
2021-04-14 8:18 ` Jason Wang
2021-04-16 3:24 ` Jason Wang
[not found] ` <20210331080519.172-4-xieyongji@bytedance.com>
2021-04-09 16:15 ` [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost device iotlb Michael S. Tsirkin
[not found] ` <CACycT3tPWwpGBNEqiL4NPrwGZhmUtAVHUZMOdbSHzjhN-ytg_A@mail.gmail.com>
2021-04-11 20:48 ` Michael S. Tsirkin
[not found] ` <CACycT3v5Z8s9_pL79m0FY5jxx3fTRHHbtARfg0On3xTnNCOdkg@mail.gmail.com>
2021-04-12 9:00 ` Michael S. Tsirkin
2021-04-14 7:34 ` [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace Michael S. Tsirkin
2021-04-14 7:49 ` Jason Wang
[not found] ` <20210331080519.172-11-xieyongji@bytedance.com>
2021-04-08 7:18 ` [PATCH v6 10/10] Documentation: Add documentation for VDUSE Jason Wang
2021-04-14 14:14 ` Stefan Hajnoczi
[not found] ` <CACycT3uNR+nZY5gY0UhPkeOyi7Za6XkX4b=hasuDcgqdc7fqfg@mail.gmail.com>
2021-04-15 7:19 ` Stefan Hajnoczi
2021-04-15 8:36 ` Jason Wang
2021-04-15 9:04 ` Jason Wang
[not found] ` <CACycT3tL7URz3n-KhMAwYH+Sn1e1TSyfU+RKcc8jpPDJ7WcZ2w@mail.gmail.com>
2021-04-16 2:20 ` Jason Wang
[not found] ` <CACycT3tyksBYxgbQLFJ-mFCKkaWotucM5_ho_K3q4wMpR0P=gw@mail.gmail.com>
2021-04-16 3:02 ` Jason Wang
2021-04-15 14:38 ` Stefan Hajnoczi [this message]
2021-04-16 2:23 ` Jason Wang
[not found] ` <CACycT3u_qAE=D_ezLPU9SpXPMACErmpqpH5pMg0TZAb3CZVGdg@mail.gmail.com>
2021-04-16 5:39 ` Jason Wang
[not found] ` <CACycT3tRN1n_PJm1mu3=s1dK941Pac15cpaysqZZKLR6xKaXSg@mail.gmail.com>
2021-04-15 14:17 ` Re: " Stefan Hajnoczi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YHhP4i+yXgA2KkVJ@stefanha-x1.localdomain \
--to=stefanha@redhat.com \
--cc=axboe@kernel.dk \
--cc=bcrl@kvack.org \
--cc=christian.brauner@canonical.com \
--cc=corbet@lwn.net \
--cc=dan.carpenter@oracle.com \
--cc=hch@infradead.org \
--cc=jasowang@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=mika.penttila@nextfour.com \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=rdunlap@infradead.org \
--cc=viro@zeniv.linux.org.uk \
--cc=virtualization@lists.linux-foundation.org \
--cc=willy@infradead.org \
--cc=xieyongji@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).