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

[Maxime Coquelin]

On 6/7/23 10:05, David Marchand wrote:
> 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.

Right, I mention it in the cover letter, but it should be in the release
note also. I propose to append this to the release note:
"While VDUSE support is already available in upstream Kernel, a couple
of patches are required to support network device type, which are being
upstreamed: 
https://lore.kernel.org/all/20230419134329.346825-1-maxime.coquelin@redhat.com/"

Does that sound good to you?

Thanks,
Maxime

> 
> 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>
> 
>