On Thu, Apr 11, 2019 at 07:02:15PM +0200, Cornelia Huck wrote: > On Thu, 11 Apr 2019 14:01:54 +0300 > Yuval Shaia <yuval.shaia@xxxxxxxxxx> wrote: > > > Data center backends use more and more RDMA or RoCE devices and more and > > more software runs in virtualized environment. > > There is a need for a standard to enable RDMA/RoCE on Virtual Machines. > > > > Virtio is the optimal solution since is the de-facto para-virtualizaton > > technology and also because the Virtio specification > > allows Hardware Vendors to support Virtio protocol natively in order to > > achieve bare metal performance. > > > > This RFC is an effort to addresses challenges in defining the RDMA/RoCE > > Virtio Specification and a look forward on possible implementation > > techniques. > > > > Open issues/Todo list: > > List is huge, this is only start point of the project. > > Anyway, here is one example of item in the list: > > - Multi VirtQ: Every QP has two rings and every CQ has one. This means that > > in order to support for example 32K QPs we will need 64K VirtQ. Not sure > > that this is reasonable so one option is to have one for all and > > multiplex the traffic on it. This is not good approach as by design it > > introducing an optional starvation. Another approach would be multi > > queues and round-robin (for example) between them. > > > > Expectations from this posting: > > In general, any comment is welcome, starting from hey, drop this as it is a > > very bad idea, to yeah, go ahead, we really want it. > > Idea here is that since it is not a minor effort i first want to know if > > there is some sort interest in the community for such device. > > My first reaction is: Sounds sensible, but it would be good to have a > spec for this :) > > You'll need a spec if you want this to go forward anyway, so at least a > sketch would be good to answer questions such as how many virtqueues > you use for which purpose, what is actually put on the virtqueues, > whether there are negotiable features, and what the expectations for > the device and the driver are. It also makes it easier to understand > how this is supposed to work in practice. > > If folks agree that this sounds useful, the next step would be to > reserve an id for the device type. Thanks for the tips, will sure do that, it is that first i wanted to make sure there is a use case here. Waiting for any feedback from the community. > > > > > The scope of the implementation is limited to probing the device and doing > > some basic ibverbs commands. Data-path is not yet implemented. So with this > > one can expect only that driver is (partialy) loaded and basic queries and > > resource allocation is done. > > > > One note regarding the patchset. > > I know it is not standard to collaps patches from several repos as i did > > here (qemu and linux) but decided to do it anyway so the whole picture can > > be seen. > > > > patch 1: virtio-net: Move some virtio-net-pci decl to include/hw/virtio > > This is a prelimenary patch just as a hack so i will not need to > > impelement new netdev > > patch 2: hw/virtio-rdma: VirtIO rdma device > > The implementation of the device > > patch 3: RDMA/virtio-rdma: VirtIO rdma driver > > The device driver > > >
