Re: [PATCH 0/4] Add multi-cid support for vsock driver

On Mon, Aug 02, 2021 at 08:07:16PM +0800, fuguancheng wrote:

This patchset enables the user to specify additional CIDS for host and
guest when booting up the guest machine. The guest's additional CIDS cannot
be repeated, and can be used to communicate with the host. The user can
also choose to specify a set of additional host cids, which can be
used to communicate with the guest who specify them. The original
CID(VHOST_DEFAULT_CID) is still available for host. The guest cid field is
deleted.

To ensure that multiple guest CID maps to the same vhost_vsock struct,
a struct called vhost_vsock_ref is added.  The function of vhost_vsock_ref
is simply used to allow multiple guest CIDS map to the
same vhost_vsock struct.

If not specified, the host and guest will now use the first CID specified
in the array for connect operation. If the host or guest wants to use
one specific CID, the bind operation can be performed before the connect
operation so that the vsock_auto_bind operation can be avoided.

Hypervisors such as qemu needs to be modified to use this feature. The
required changes including at least the following:
1. Invoke the modified ioctl call with the request code
VHOST_VSOCK_SET_GUEST_CID. Also see struct multi_cid_message for
arguments used in this ioctl call.
2. Write new arguments to the emulated device config space.
3. Modify the layout of the data written to the device config space.
See struct virtio_vsock_config for reference.

I have tested this setup with iperf3.  The communication between host
and guest using original CID or additional CIDS worked normally.
Not tested in extreme conditions where memory is insufficient.

Linux kernel newbies here, any suggestions are welcomed.
Thanks in advance!

Could you supply a bit info about the motivation for this feature?
I wonder whether it's be better to have multiple VQs
instead of tweaking the CID in the message header.

fuguancheng (4):
  VSOCK DRIVER: Add multi-cid support for guest
  VSOCK DRIVER: support communication using additional guest cid
  VSOCK DRIVER: support specifying additional cids for host
  VSOCK DRIVER: support communication using host additional cids

 drivers/vhost/vsock.c                   | 338 ++++++++++++++++++++++++++++----
 include/net/af_vsock.h                  |   5 +
 include/uapi/linux/vhost.h              |   9 +
 include/uapi/linux/virtio_vsock.h       |   8 +-
 net/vmw_vsock/af_vsock.c                |  28 ++-
 net/vmw_vsock/virtio_transport.c        | 129 +++++++++++-
 net/vmw_vsock/virtio_transport_common.c |   5 +-
 net/vmw_vsock/vsock_loopback.c          |   8 +
 8 files changed, 471 insertions(+), 59 deletions(-)

-- 
2.11.0