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

[Xia, Chenbo]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Wednesday, June 7, 2023 10:59 PM
> To: Xia, Chenbo <chenbo.xia at intel.com>; dev at dpdk.org;
> david.marchand at redhat.com; mkp at redhat.com; fbl at redhat.com;
> jasowang at redhat.com; Liang, Cunming <cunming.liang at intel.com>; Xie, Yongji
> <xieyongji at bytedance.com>; echaudro at redhat.com; eperezma at redhat.com;
> amorenoz at redhat.com; lulu at redhat.com
> Subject: Re: [PATCH v5 00/26] Add VDUSE support to Vhost library
> 
> 
> 
> On 6/7/23 08:48, Xia, Chenbo wrote:
> > Hi Maxime,
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> >> Sent: Tuesday, June 6, 2023 4:18 PM
> >> To: dev at dpdk.org; Xia, Chenbo <chenbo.xia at intel.com>;
> >> david.marchand at redhat.com; mkp at redhat.com; fbl at redhat.com;
> >> jasowang at redhat.com; Liang, Cunming <cunming.liang at intel.com>; Xie,
> Yongji
> >> <xieyongji at bytedance.com>; echaudro at redhat.com; eperezma at redhat.com;
> >> amorenoz at redhat.com; lulu at redhat.com
> >> Cc: Maxime Coquelin <maxime.coquelin at redhat.com>
> >> Subject: [PATCH v5 00/26] Add VDUSE support to Vhost library
> >>
> >> 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 v5:
> >> ==============
> >> - Delay starting/stopping the device to after having replied to the
> VDUSE
> >>    event in order to avoid a deadlock encountered when testing with OVS.
> >
> > Could you explain more to help me understand the deadlock issue?
> 
> Sure.
> 
> The V5 fixes an ABBA deadlock involving OVS mutex and kernel
> rtnl_lock(), two OVS threads and the vdpa tool process.
> 
> We have an OVS bridge with a mlx5 port already added.
> We add the vduse port to the same bridge.
> Then we use the iproute2 vdpa tool to attach the vduse device the the
> kernel vdpa bus. when doing this the rtnl lock is taken when the virtio-
> net device is probed, and VDUSE_SET_STATUS gets sent and waits for its
> reply.
> 
> This VDUSE_SET_STATUS request is handled by the DPDK VDUSE event
> handler, and if DRIVER_OK bit is set the Vhsot .new_device() callback is
> called, which triggers a bridge reconfiguration.
> 
> On bridge reconfiguration, the mlx5 port takes the OVS mutex and
> performs an ioctl() which tries to take the rtnl lock, but is is already
> owned by the vdpa tool.
> 
> The vduse_events thread is stucked waiting for the OVS mutex, so the
> reply to the VDUSE_SET_STATUS event is never sent, and the vdpa tool
> process is stucked for 30 seconds, until a timeout happens.
> 
> When the timeourt happen, everything is unblocked, but the VDUSE device
> has been marked as broken, and so not usable anymore.
> 
> I could reproduce and provide you the backtraces of the different
> threads if you wish.
> 
> Anyway, I think it makes sense to perform the device startup after
> having replied to VDUSE_SET_STATUS request, as it just mean the device
> has taken into account the new status of the driver.
> 
> Hope it clarifies, let me know if you need more details.

It's very clear! Thanks Maxime for the explanation!

/Chenbo

> 
> Thanks,
> Maxime
> 
> > Thanks,
> > Chenbo
> >
> >> - Mention reconnection support lack in the release note.
> >>
> >> Changes in v4:
> >> ==============
> >> - Applied patch 1 and patch 2 from v3
> >> - Rebased on top of Eelco series
> >> - Fix coredump clear in IOTLB cache removal (David)
> >> - Remove uneeded ret variable in vhost_vring_inject_irq (David)
> >> - Fixed release note (David, Chenbo)
> >>
> >> 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 (26):
> >>    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 |  12 +
> >>   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                  |   1 +
> >>   lib/vhost/vhost.c                      |  70 ++-
> >>   lib/vhost/vhost.h                      |  57 ++-
> >>   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, 1409 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
> >>
> >> --
> >> 2.40.1
> >