Re: Re: [RFC v1 0/6] virtio/vsock: introduce SOCK_DGRAM support

[Jiang Wang .]

On Wed, Jun 9, 2021 at 6:51 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> 在 2021/6/10 上午7:24, Jiang Wang 写道:
> > This patchset implements support of SOCK_DGRAM for virtio
> > transport.
> >
> > Datagram sockets are connectionless and unreliable. To avoid unfair contention
> > with stream and other sockets, add two more virtqueues and
> > a new feature bit to indicate if those two new queues exist or not.
> >
> > Dgram does not use the existing credit update mechanism for
> > stream sockets. When sending from the guest/driver, sending packets
> > synchronously, so the sender will get an error when the virtqueue is full.
> > When sending from the host/device, send packets asynchronously
> > because the descriptor memory belongs to the corresponding QEMU
> > process.
>
>
> What's the use case for the datagram vsock?
>
One use case is for non critical info logging from the guest
to the host, such as the performance data of some applications.

It can also be used to replace UDP communications between
the guest and the host.

> >
> > The virtio spec patch is here:
> > https://www.spinics.net/lists/linux-virtualization/msg50027.html
>
>
> Have a quick glance, I suggest to split mergeable rx buffer into an
> separate patch.

Sure.

> But I think it's time to revisit the idea of unifying the virtio-net and
> virtio-vsock. Otherwise we're duplicating features and bugs.

For mergeable rxbuf related code, I think a set of common helper
functions can be used by both virtio-net and virtio-vsock. For other
parts, that may not be very beneficial. I will think about more.

If there is a previous email discussion about this topic, could you send me
some links? I did a quick web search but did not find any related
info. Thanks.

> Thanks
>
>
> >
> > For those who prefer git repo, here is the link for the linux kernel：
> > https://github.com/Jiang1155/linux/tree/vsock-dgram-v1
> >
> > qemu patch link:
> > https://github.com/Jiang1155/qemu/tree/vsock-dgram-v1
> >
> >
> > To do:
> > 1. use skb when receiving packets
> > 2. support multiple transport
> > 3. support mergeable rx buffer
> >
> >
> > Jiang Wang (6):
> >    virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit
> >    virtio/vsock: add support for virtio datagram
> >    vhost/vsock: add support for vhost dgram.
> >    vsock_test: add tests for vsock dgram
> >    vhost/vsock: add kconfig for vhost dgram support
> >    virtio/vsock: add sysfs for rx buf len for dgram
> >
> >   drivers/vhost/Kconfig                              |   8 +
> >   drivers/vhost/vsock.c                              | 207 ++++++++--
> >   include/linux/virtio_vsock.h                       |   9 +
> >   include/net/af_vsock.h                             |   1 +
> >   .../trace/events/vsock_virtio_transport_common.h   |   5 +-
> >   include/uapi/linux/virtio_vsock.h                  |   4 +
> >   net/vmw_vsock/af_vsock.c                           |  12 +
> >   net/vmw_vsock/virtio_transport.c                   | 433 ++++++++++++++++++---
> >   net/vmw_vsock/virtio_transport_common.c            | 184 ++++++++-
> >   tools/testing/vsock/util.c                         | 105 +++++
> >   tools/testing/vsock/util.h                         |   4 +
> >   tools/testing/vsock/vsock_test.c                   | 195 ++++++++++
> >   12 files changed, 1070 insertions(+), 97 deletions(-)
> >
>