Re: [PATCH rdma-next 00/11] Elastic RDMA Adapter (ERDMA) driver

[Leon Romanovsky <leon@kernel.org>]

On Thu, Dec 23, 2021 at 08:59:14PM +0800, Cheng Xu wrote:
> 
> 
> On 12/23/21 6:23 PM, Leon Romanovsky wrote:
> > On Wed, Dec 22, 2021 at 11:35:44AM +0800, Cheng Xu wrote:
> > > 
> > 
> > <...>
> > 
> > > > > 
> > > > > For the ECS instance with RDMA enabled, there are two kinds of devices
> > > > > allocated, one for ERDMA, and one for the original netdev (virtio-net).
> > > > > They are different PCI deivces. ERDMA driver can get the information about
> > > > > which netdev attached to in its PCIe barspace (by MAC address matching).
> > > > 
> > > > This is very questionable. The netdev part should be kept in the
> > > > drivers/ethernet/... part of the kernel.
> > > > 
> > > > Thanks
> > > 
> > > The net device used in Alibaba ECS instance is virtio-net device, driven
> > > by virtio-pci/virtio-net drivers. ERDMA device does not need its own net
> > > device, and will be attached to an existed virtio-net device. The
> > > relationship between ibdev and netdev in erdma is similar to siw/rxe.
> > 
> > siw/rxe binds through RDMA_NLDEV_CMD_NEWLINK netlink command and not
> > through MAC's matching.
> > 
> > Thanks
> 
> Both siw/rxe/erdma don't need to implement netdev part, this is what I
> wanted to express when I said 'similar'.
> What you mentioned (the bind mechanism) is one major difference between
> erdma and siw/rxe. For siw/rxe, user can attach ibdev to every netdev if
> he/she wants, but it is not true for erdma. When user buys the erdma
> service, he/she must specify which ENI (elastic network interface) to be
> binded, it means that the attached erdma device can only be binded to
> the specific netdev. Due to the uniqueness of MAC address in our ECS
> instance, we use the MAC address as the identification, then the driver
> knows which netdev should be binded to.

Nothing prohibits from you to implement this MAC check in RDMA_NLDEV_CMD_NEWLINK.
I personally don't like the idea that bind logic is performed "magically".

BTW,
1. No module parameters
2. No driver versions

Thanks

> 
> Thanks,
> Cheng Xu