> From: Jakub Kicinski <kuba@xxxxxxxxxx> > Sent: Friday, November 20, 2020 9:05 AM > > On Thu, 19 Nov 2020 10:00:17 -0400 Jason Gunthorpe wrote: > > Finally, in the mlx5 model VDPA is just an "application". It asks the > > device to create a 'RDMA' raw ethernet packet QP that is uses rings > > formed in the virtio-net specification. We can create it in the kernel > > using mlx5_vdpa, and we can create it in userspace through the RDMA > > subsystem. Like any "RDMA" application it is contained by the security > > boundary of the PF/VF/SF the mlx5_core is running on. > > Thanks for the write up! > > The SF part is pretty clear to me, it is what it is. DPDK camp has been pretty > excited about ADI/PASID for a while now. > > > The part that's blurry to me is VDPA. > > I was under the impression that for VDPA the device is supposed to support > native virtio 2.0 (or whatever the "HW friendly" spec was). > > I believe that's what the early patches from Intel did. > > You're saying it's a client application like any other - do I understand it right that > the hypervisor driver will be translating descriptors between virtio and device- > native then? > mlx5 device support virtio descriptors natively. So no need of translation. > The vdpa parent is in the hypervisor correct? > Yep. > Can a VDPA device have multiple children of the same type? > I guess, you mean VDPA parentdev? If so, yes, however at present we see only one_to_one mapping of vdpa device and parent dev. > Why do we have a representor for a SF, if the interface is actually VDPA? Because vdpa is just one client out of multiple. At the moment there is one to one relation of vdpa device to a SF/VF. > Block and net traffic can't reasonably be treated the same by the switch. > > Also I'm confused how block device can bind to mlx5_core - in that case I'm > assuming the QP is bound 1:1 with a QP on the SmartNIC side, and that QP is > plugged into an appropriate backend? So far there isn't mlx5_vdpa.ko or plan to do block. But yes, in future for block, it needs to bind to a QP in backend in smartnic.
