From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [RFC 0/3] VirtIO RDMA Date: Thu, 11 Apr 2019 17:24:08 +0000 Message-ID: <20190411172402.GA14509@mellanox.com> References: <20190411110157.14252-1-yuval.shaia@oracle.com> <20190411190215.2163572e.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20190411190215.2163572e.cohuck@redhat.com> Content-Language: en-US Content-ID: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" To: Cornelia Huck Cc: "mst@redhat.com" , "linux-rdma@vger.kernel.org" , "qemu-devel@nongnu.org" , Yuval Shaia , "virtualization@lists.linux-foundation.org" List-Id: linux-rdma@vger.kernel.org On Thu, Apr 11, 2019 at 07:02:15PM +0200, Cornelia Huck wrote: > On Thu, 11 Apr 2019 14:01:54 +0300 > Yuval Shaia wrote: >=20 > > Data center backends use more and more RDMA or RoCE devices and more an= d > > more software runs in virtualized environment. > > There is a need for a standard to enable RDMA/RoCE on Virtual Machines. > >=20 > > 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. > >=20 > > This RFC is an effort to addresses challenges in defining the RDMA/RoCE > > Virtio Specification and a look forward on possible implementation > > techniques. > >=20 > > 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 s= ure > > 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 i= t > > introducing an optional starvation. Another approach would be multi > > queues and round-robin (for example) between them. > >=20 > > 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 i= f > > there is some sort interest in the community for such device. >=20 > My first reaction is: Sounds sensible, but it would be good to have a > spec for this :) I'm unclear why you'd want to have a virtio queue for anything other that some kind of command channel. I'm not sure a QP or CQ benefits from this?? Jason