From: Jason Wang <jasowang@redhat.com>
To: Yongji Xie <xieyongji@bytedance.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>,
"Christian Brauner" <christian.brauner@canonical.com>,
bcrl@kvack.org, viro@zeniv.linux.org.uk,
"Stefan Hajnoczi" <stefanha@redhat.com>,
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: Fri, 16 Apr 2021 13:39:45 +0800 [thread overview]
Message-ID: <fab615ce-5e13-a3b3-3715-a4203b4ab010@redhat.com> (raw)
In-Reply-To: <CACycT3u_qAE=D_ezLPU9SpXPMACErmpqpH5pMg0TZAb3CZVGdg@mail.gmail.com>
在 2021/4/16 上午11:19, Yongji Xie 写道:
> On Fri, Apr 16, 2021 at 10:24 AM Jason Wang <jasowang@redhat.com> wrote:
>>
>> 在 2021/4/15 下午10:38, Stefan Hajnoczi 写道:
>>> 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.
>>
>> +1
>>
>>
>>> 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.
>>
>> Yes, so the case of VDUSE is something similar to the case of e.g SEV.
>>
>> Both cases won't trust device and use some kind of software IOTLB.
>>
>> That means we need to protect at both IOTLB and virtio drivers.
>>
>> Let me post patches for virtio first.
>>
> Looking forward your patches.
>
> Thanks.
> Yongji
>
Fortuantely, packed ring has already did this since the descriptor talbe
is expected to be re-wrote by the device. I just need to conver the
split ring.
Thanks
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-04-16 5:40 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
2021-04-16 2:23 ` Jason Wang
[not found] ` <CACycT3u_qAE=D_ezLPU9SpXPMACErmpqpH5pMg0TZAb3CZVGdg@mail.gmail.com>
2021-04-16 5:39 ` Jason Wang [this message]
[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=fab615ce-5e13-a3b3-3715-a4203b4ab010@redhat.com \
--to=jasowang@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=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=stefanha@redhat.com \
--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).