Re: [virtio-dev] Re: [RFC] Virtio RDMA

[Junji Wei <weijunji@bytedance.com>]

> On Feb 16, 2022, at 1:54 PM, Jason Wang <jasowang@redhat.com> wrote:
> 
> On Tue, Feb 15, 2022 at 6:02 PM Junji Wei <weijunji@bytedance.com> wrote:
>> 
>> 
>>> On Feb 15, 2022, at 4:44 PM, Jason Wang <jasowang@redhat.com> wrote:
>>> 
>>> On Tue, Feb 15, 2022 at 4:15 PM Junji Wei <weijunji@bytedance.com> wrote:
>>>> 
>>>> Hi all,
>>>> 
>>>> This RFC aims to introduce our recent work on VirtIO-RDMA.
>>>> 
>>>> We have finished a draft of VirtIO-RDMA specification and a vhost-user
>>>> RDMA demo based on the spec.This demo can work with CM/Socket
>>>> and UD/RC QP now.
>>>> 
>>>> NOTE that this spec now only focuses on emulating a soft
>>>> RoCE (RDMA over Converged Ethernet) device with normal Network Interface
>>>> Card (without RDMA capability). So most Infiniband (IB) specific features
>>>> such as Subnet Manager (SM), Local Identifier (LID) and Automatic Path
>>>> Migration (APM) are not covered in this specification.
>>>> 
>>>> There are four parts of our work:
>>>> 
>>>> 1. VirtIO-RDMA driver in linux kernel:
>>>> https://github.com/weijunji/linux/tree/virtio-rdma-patch
>>>> 
>>>> 2. VirtIO-RDMA userspace provider in rdma-core:
>>>> https://github.com/weijunji/rdma-core/tree/virtio-rdma
>>>> 
>>>> 3. VHost-User RDMA backend in QEMU:
>>>> https://github.com/weijunji/qemu/tree/vhost-user-rdma
>>>> 
>>>> 4. VHost-User RDMA demo implements with DPDK:
>>>> https://github.com/weijunji/dpdk-rdma
>>>> 
>>>> 
>>>> To test with our demo:
>>>> 
>>>> 1. Build Linux kernel with config INFINIBAND_VIRTIO_RDMA
>>>> 
>>>> 2. Build QEMU with config VHOST_USER_RDMA
>>>> 
>>>> 3. Build rdma-core and install it to VM image
>>>> 
>>>> 4. Build and install DPDK(NOTE that we only tested on DPDK 20.11.3)
>>>> 
>>>> 5. Build dpdk-rdma:
>>>>   $ cd dpdk-rdma
>>>>   $ meson build
>>>>   $ cd build
>>>>   $ ninja
>>>> 
>>>> 6. Run dpdk-rdma:
>>>>   $ sudo ./dpdk-rdma --vdev 'net_vhost0,iface=/tmp/sock0,queues=1' \
>>>>     --vdev 'net_tap0' --lcore '1-3'
>>>>   $ sudo brctl addif virbr0 dtap0
>>>> 
>>>> 7. Boot kernel with qemu with following args using libvirt:
>>>> <qemu:commandline>
>>>>   <qemu:arg value='-chardev'/>
>>>>   <qemu:arg value='socket,path=/tmp/sock0,id=vunet'/>
>>>>   <qemu:arg value='-netdev'/>
>>>>   <qemu:arg value='vhost-user,id=net1,chardev=vunet,vhostforce,queues=1'/>
>>>>   <qemu:arg value='-device'/>
>>>>   <qemu:arg value='virtio-net-pci,netdev=net1,bus=pci.0,multifunction=on,addr=0x2'/>
>>>>   <qemu:arg value='-chardev'/>
>>>>   <qemu:arg value='socket,path=/tmp/vhost-rdma0,id=vurdma'/>
>>>>   <qemu:arg value='-device'/>
>>>>   <qemu:arg value='vhost-user-rdma-pci,page-per-vq,disable-legacy=on,addr=2.1,chardev=vurdma'/>
>>>> </qemu:commandline>
>>>> 
>>>> NOTE that virtio-net-pci and vhost-user-rdma-pci MUST in same PCI addresss.
>>>> 
>>> 
>>> A silly question, if RoCE is the focus, why not extending virtio-net instead?
>> 
>> I think it's OK to extend virtio-net to implement virtio-rdma. But if we want to
>> support IB in the future, would it be better to implement the virtio-rdma in an
>> independent way?
> 
> I'm not sure but a question is whether IB is useful to be visible by
> the guest. E.g can you implement the soft RoCE backend via IB
> hardware?

We can't. So do you mean we can implement virtio-rdma only for IB in the future?

>> And currently virtio-rdma doesn't have a strong dependency on
>> virtio-net (except for gid and ah stuffs). Is it OK to mix them up?
> 
> There are a bunch of hardware vendors that ship a converged Ethernet
> adapter. It simplifies the management and deployment.

Virtio-rdma is not depend on virtio-net, we can bind it to another ethernet device
via mac address in the future. And is it too mass to mix up two different device
in one spec?