Subject: Re: [RFC v4 0/5] Add virtio transport for AF_VSOCK

From: Jason Wang <[email-masked]>
Date: Mon, 4 Jan 2016 15:55:35 +0800

On 12/22/2015 05:07 PM, Stefan Hajnoczi wrote:
> This series is based on v4.4-rc2 and the "virtio: make find_vqs()
> checkpatch.pl-friendly" patch I recently submitted.
>
> v4:
>  * Addressed code review comments from Alex Bennee
>  * MAINTAINERS file entries for new files
>  * Trace events instead of pr_debug()
>  * RST packet is sent when there is no listen socket
>  * Allow guest->host connections again (began discussing netfilter support with
>    Matt Benjamin instead of hard-coding security policy in virtio-vsock code)
>  * Many checkpatch.pl cleanups (will be 100% clean in v5)
>
> v3:
>  * Remove unnecessary 3-way handshake, just do REQUEST/RESPONSE instead
>    of REQUEST/RESPONSE/ACK
>  * Remove SOCK_DGRAM support and focus on SOCK_STREAM first
>    (also drop v2 Patch 1, it's only needed for SOCK_DGRAM)
>  * Only allow host->guest connections (same security model as latest
>    VMware)
>  * Don't put vhost vsock driver into staging
>  * Add missing Kconfig dependencies (Arnd Bergmann <[email-masked]>)
>  * Remove unneeded variable used to store return value
>    (Fengguang Wu <[email-masked]> and Julia Lawall
>    <[email-masked]>)
>
> v2:
>  * Rebased onto Linux v4.4-rc2
>  * vhost: Refuse to assign reserved CIDs
>  * vhost: Refuse guest CID if already in use
>  * vhost: Only accept correctly addressed packets (no spoofing!)
>  * vhost: Support flexible rx/tx descriptor layout
>  * vhost: Add missing total_tx_buf decrement
>  * virtio_transport: Fix total_tx_buf accounting
>  * virtio_transport: Add virtio_transport global mutex to prevent races
>  * common: Notify other side of SOCK_STREAM disconnect (fixes shutdown
>    semantics)
>  * common: Avoid recursive mutex_lock(tx_lock) for write_space (fixes deadlock)
>  * common: Define VIRTIO_VSOCK_TYPE_STREAM/DGRAM hardware interface constants
>  * common: Define VIRTIO_VSOCK_SHUTDOWN_RCV/SEND hardware interface constants
>  * common: Fix peer_buf_alloc inheritance on child socket
>
> This patch series adds a virtio transport for AF_VSOCK (net/vmw_vsock/).
> AF_VSOCK is designed for communication between virtual machines and
> hypervisors.  It is currently only implemented for VMware's VMCI transport.
>
> This series implements the proposed virtio-vsock device specification from
> here:
> http://permalink.gmane.org/gmane.comp.emulators.virtio.devel/980
>
> Most of the work was done by Asias He and Gerd Hoffmann a while back.  I have
> picked up the series again.
>
> The QEMU userspace changes are here:
> https://github.com/stefanha/qemu/commits/vsock
>
> Why virtio-vsock?
> -----------------
> Guest<->host communication is currently done over the virtio-serial device.
> This makes it hard to port sockets API-based applications and is limited to
> static ports.
>
> virtio-vsock uses the sockets API so that applications can rely on familiar
> SOCK_STREAM semantics.  Applications on the host can easily connect to guest
> agents because the sockets API allows multiple connections to a listen socket
> (unlike virtio-serial).  This simplifies the guest<->host communication and
> eliminates the need for extra processes on the host to arbitrate virtio-serial
> ports.
>
> Overview
> --------
> This series adds 3 pieces:
>
> 1. virtio_transport_common.ko - core virtio vsock code that uses vsock.ko
>
> 2. virtio_transport.ko - guest driver
>
> 3. drivers/vhost/vsock.ko - host driver

Have a (dumb maybe) question after a quick glance at the codes:

Is there any chance to reuse existed virtio-net/vhost-net codes? For
example, using virito-net instead of a new device as a transport in
guest and using vhost-net (especially consider it uses a socket as
backend) in host. Maybe just a new virtio-net header type for vsock. I'm
asking since I don't see any blocker for doing this.

Thanks

> Howto
> -----
> The following kernel options are needed:
>   CONFIG_VSOCKETS=y
>   CONFIG_VIRTIO_VSOCKETS=y
>   CONFIG_VIRTIO_VSOCKETS_COMMON=y
>   CONFIG_VHOST_VSOCK=m
>
> Launch QEMU as follows:
>   # qemu ... -device vhost-vsock-pci,id=vhost-vsock-pci0,guest-cid=3
>
> Guest and host can communicate via AF_VSOCK sockets.  The host's CID (address)
> is 2 and the guest must be assigned a CID (3 in the example above).
>
> Status
> ------
> This patch series implements the latest draft specification.  Please review.
>
> Asias He (4):
>   VSOCK: Introduce virtio_vsock_common.ko
>   VSOCK: Introduce virtio_transport.ko
>   VSOCK: Introduce vhost_vsock.ko
>   VSOCK: Add Makefile and Kconfig
>
> Stefan Hajnoczi (1):
>   VSOCK: transport-specific vsock_transport functions
>
>  MAINTAINERS                                        |  13 +
>  drivers/vhost/Kconfig                              |  15 +
>  drivers/vhost/Makefile                             |   4 +
>  drivers/vhost/vsock.c                              | 607 +++++++++++++++
>  drivers/vhost/vsock.h                              |   4 +
>  include/linux/virtio_vsock.h                       | 167 +++++
>  include/net/af_vsock.h                             |   3 +
>  .../trace/events/vsock_virtio_transport_common.h   | 144 ++++
>  include/uapi/linux/virtio_ids.h                    |   1 +
>  include/uapi/linux/virtio_vsock.h                  |  87 +++
>  net/vmw_vsock/Kconfig                              |  19 +
>  net/vmw_vsock/Makefile                             |   2 +
>  net/vmw_vsock/af_vsock.c                           |   9 +
>  net/vmw_vsock/virtio_transport.c                   | 481 ++++++++++++
>  net/vmw_vsock/virtio_transport_common.c            | 834 +++++++++++++++++++++
>  15 files changed, 2390 insertions(+)
>  create mode 100644 drivers/vhost/vsock.c
>  create mode 100644 drivers/vhost/vsock.h
>  create mode 100644 include/linux/virtio_vsock.h
>  create mode 100644 include/trace/events/vsock_virtio_transport_common.h
>  create mode 100644 include/uapi/linux/virtio_vsock.h
>  create mode 100644 net/vmw_vsock/virtio_transport.c
>  create mode 100644 net/vmw_vsock/virtio_transport_common.c
>