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

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Date:   Mon, 2 Aug 2021 16:21:36 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     fuguancheng <fuguancheng@...edance.com>
Cc:     jasowang@...hat.com, stefanha@...hat.com, sgarzare@...hat.com,
        davem@...emloft.net, kuba@...nel.org, arseny.krasnov@...persky.com,
        andraprs@...zon.com, colin.king@...onical.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: 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
> 
>