[PATCH v5 00/26] Add VDUSE support to Vhost library

[David Marchand]

On Tue, Jun 6, 2023 at 10:19 AM Maxime Coquelin
<maxime.coquelin at redhat.com> wrote:
>
> This series introduces a new type of backend, VDUSE,
> to the Vhost library.
>
> VDUSE stands for vDPA device in Userspace, it enables
> implementing a Virtio device in userspace and have it
> attached to the Kernel vDPA bus.
>
> Once attached to the vDPA bus, it can be used either by
> Kernel Virtio drivers, like virtio-net in our case, via
> the virtio-vdpa driver. Doing that, the device is visible
> to the Kernel networking stack and is exposed to userspace
> as a regular netdev.
>
> It can also be exposed to userspace thanks to the
> vhost-vdpa driver, via a vhost-vdpa chardev that can be
> passed to QEMU or Virtio-user PMD.
>
> While VDUSE support is already available in upstream
> Kernel, a couple of patches are required to support
> network device type:
>
> https://gitlab.com/mcoquelin/linux/-/tree/vduse_networking_rfc
>
> In order to attach the created VDUSE device to the vDPA
> bus, a recent iproute2 version containing the vdpa tool is
> required.
>
> Benchmark results:
> ==================
>
> On this v2, PVP reference benchmark has been run & compared with
> Vhost-user.
>
> When doing macswap forwarding in the worload, no difference is seen.
> When doing io forwarding in the workload, we see 4% performance
> degradation with VDUSE, comapred to Vhost-user/Virtio-user. It is
> explained by the use of the IOTLB layer in the Vhost-library when using
> VDUSE, whereas Vhost-user/Virtio-user does not make use of it.
>
> Usage:
> ======
>
> 1. Probe required Kernel modules
> # modprobe vdpa
> # modprobe vduse
> # modprobe virtio-vdpa
>
> 2. Build (require vduse kernel headers to be available)
> # meson build
> # ninja -C build
>
> 3. Create a VDUSE device (vduse0) using Vhost PMD with
> testpmd (with 4 queue pairs in this example)
> # ./build/app/dpdk-testpmd --no-pci --vdev=net_vhost0,iface=/dev/vduse/vduse0,queues=4 --log-level=*:9  -- -i --txq=4 --rxq=4

9 is a nice but undefined value. 8 is enough.
In general, I prefer "human readable" strings, like *:debug ;-).


>
> 4. Attach the VDUSE device to the vDPA bus
> # vdpa dev add name vduse0 mgmtdev vduse
> => The virtio-net netdev shows up (eth0 here)
> # ip l show eth0
> 21: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
>     link/ether c2:73:ea:a7:68:6d brd ff:ff:ff:ff:ff:ff
>
> 5. Start/stop traffic in testpmd
> testpmd> start
> testpmd> show port stats 0
>   ######################## NIC statistics for port 0  ########################
>   RX-packets: 11         RX-missed: 0          RX-bytes:  1482
>   RX-errors: 0
>   RX-nombuf:  0
>   TX-packets: 1          TX-errors: 0          TX-bytes:  62
>
>   Throughput (since last show)
>   Rx-pps:            0          Rx-bps:            0
>   Tx-pps:            0          Tx-bps:            0
>   ############################################################################
> testpmd> stop
>
> 6. Detach the VDUSE device from the vDPA bus
> # vdpa dev del vduse0
>
> 7. Quit testpmd
> testpmd> quit
>
> Known issues & remaining work:
> ==============================
> - Fix issue in FD manager (still polling while FD has been removed)
> - Add Netlink support in Vhost library
> - Support device reconnection
>  -> a temporary patch to support reconnection via a tmpfs file is available,
>     upstream solution would be in-kernel and is being developed.
>  -> https://gitlab.com/mcoquelin/dpdk-next-virtio/-/commit/5ad06ce14159a9ce36ee168dd13ef389cec91137
> - Support packed ring
> - Provide more performance benchmark results

We are missing a reference to the kernel patches required to have
vduse accept net devices.

I had played with the patches at v1 and it was working ok.
I did not review in depth the latest revisions, but I followed your
series from the PoC/start.
Overall, the series lgtm.

For the series,
Acked-by: David Marchand <david.marchand at redhat.com>


-- 
David Marchand