Re: [PATCH v3 00/28] Add VDUSE support to Vhost library

[David Marchand <david.marchand@redhat.com>]

On Thu, May 25, 2023 at 6:25 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
>
> Note: v2 is identical to v3, it is just a resend because
> of an issue when posting v2 breaking the series in patchwork.
>
> 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
>
> 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
>
> Changes in v2/v3:
> =================
> - Fixed mem_set_dump() parameter (patch 4)
> - Fixed accidental comment change (patch 7, Chenbo)
> - Change from __builtin_ctz to __builtin_ctzll (patch 9, Chenbo)
> - move change from patch 12 to 13 (Chenbo)
> - Enable locks annotation for control queue (Patch 17)
> - Send control queue notification when used descriptors enqueued (Patch 17)
> - Lock control queue IOTLB lock (Patch 17)
> - Fix error path in virtio_net_ctrl_pop() (Patch 17, Chenbo)
> - Set VDUSE dev FD as NONBLOCK (Patch 18)
> - Enable more Virtio features (Patch 18)
> - Remove calls to pthread_setcancelstate() (Patch 22)
> - Add calls to fdset_pipe_notify() when adding and deleting FDs from a set (Patch 22)
> - Use RTE_DIM() to get requests string array size (Patch 22)
> - Set reply result for IOTLB update message (Patch 25, Chenbo)
> - Fix queues enablement with multiqueue (Patch 26)
> - Move kickfd creation for better logging (Patch 26)
> - Improve logging (Patch 26)
> - Uninstall cvq kickfd in case of handler installation failure (Patch 27)
> - Enable CVQ notifications once handler is installed (Patch 27)
> - Don't advertise multiqueue and control queue if app only request single queue pair (Patch 27)
> - Add release notes
>
> Maxime Coquelin (28):
>   vhost: fix missing guest notif stat increment
>   vhost: fix invalid call FD handling
>   vhost: fix IOTLB entries overlap check with previous entry
>   vhost: add helper of IOTLB entries coredump
>   vhost: add helper for IOTLB entries shared page check
>   vhost: don't dump unneeded pages with IOTLB
>   vhost: change to single IOTLB cache per device
>   vhost: add offset field to IOTLB entries
>   vhost: add page size info to IOTLB entry
>   vhost: retry translating IOVA after IOTLB miss
>   vhost: introduce backend ops
>   vhost: add IOTLB cache entry removal callback
>   vhost: add helper for IOTLB misses
>   vhost: add helper for interrupt injection
>   vhost: add API to set max queue pairs
>   net/vhost: use API to set max queue pairs
>   vhost: add control virtqueue support
>   vhost: add VDUSE device creation and destruction
>   vhost: add VDUSE callback for IOTLB miss
>   vhost: add VDUSE callback for IOTLB entry removal
>   vhost: add VDUSE callback for IRQ injection
>   vhost: add VDUSE events handler
>   vhost: add support for virtqueue state get event
>   vhost: add support for VDUSE status set event
>   vhost: add support for VDUSE IOTLB update event
>   vhost: add VDUSE device startup
>   vhost: add multiqueue support to VDUSE
>   vhost: add VDUSE device stop
>
>  doc/guides/prog_guide/vhost_lib.rst    |   4 +
>  doc/guides/rel_notes/release_23_07.rst |  11 +
>  drivers/net/vhost/rte_eth_vhost.c      |   3 +
>  lib/vhost/iotlb.c                      | 333 +++++++------
>  lib/vhost/iotlb.h                      |  45 +-
>  lib/vhost/meson.build                  |   5 +
>  lib/vhost/rte_vhost.h                  |  17 +
>  lib/vhost/socket.c                     |  72 ++-
>  lib/vhost/vduse.c                      | 646 +++++++++++++++++++++++++
>  lib/vhost/vduse.h                      |  33 ++
>  lib/vhost/version.map                  |   3 +
>  lib/vhost/vhost.c                      |  51 +-
>  lib/vhost/vhost.h                      |  90 ++--
>  lib/vhost/vhost_user.c                 |  51 +-
>  lib/vhost/vhost_user.h                 |   2 +-
>  lib/vhost/virtio_net_ctrl.c            | 286 +++++++++++
>  lib/vhost/virtio_net_ctrl.h            |  10 +
>  17 files changed, 1424 insertions(+), 238 deletions(-)
>  create mode 100644 lib/vhost/vduse.c
>  create mode 100644 lib/vhost/vduse.h
>  create mode 100644 lib/vhost/virtio_net_ctrl.c
>  create mode 100644 lib/vhost/virtio_net_ctrl.h

I did not do a in-depth review, but overall, the series lgtm (and per
patch compilation looks fine).

A few comments though:
- patch 2 is the same as
https://patchwork.dpdk.org/project/dpdk/patch/168431454344.558450.2397970324914136724.stgit@ebuild.local/
It would be cool to report the review tags in the first series that
gets applied.
- there may be a bug in patch 5, see comment on patch,
- patch 4, 5 and 6 go together, with patch 6 being the fix itself. I
understand it was easier to review as splitted patches, but maybe it
would be simpler to squash them to make the backport trivial.
- patch 7 (and some other patches in the series) will increase the
virtio_net structure but we are not gaining anything on the
vhost_virtqueue size, so a device + vqs memory footprint will slightly
increase. This is not a problem afaics?
- patch 15 breaks the doc, format is incorrect but the CI reported it
so you will notice it before merging :-),


-- 
David Marchand