Re: Using RPMSG to communicate between host and guest drivers

[Jason Gunthorpe <jgg@ziepe.ca>]

On Mon, Aug 26, 2024 at 12:27:02PM -0400, Dennis Dalessandro wrote:
> On 7/31/24 4:02 PM, Doug Miller wrote:
> > I am working on SR-IOV support for a new adapter which has shared 
> > resources between the PF and VFs and requires an out-of-band (outside 
> > the adapter) communication mechanism to manage those resources. I have 
> > been looking at RPMSG as a mechanism to communicate between the driver 
> > on a guest (VM) and the driver on the host OS (which "owns" the 
> > resources). It appears to me that virtio is intended for communication 
> > between guests and host, and RPMSG over virtio is what I want to use.
> > 
> > Can anyone confirm that RPMSG is capable of doing what we need? If so, 
> > I'll need some help figuring out how to use that from kernel device 
> > drivers (I've not been able to find any examples of doing the 
> > service/device side). If not, is there some other facility that is 
> > better suited?
> 
> Hi Bjorn and Mathieu, any advice here for Doug? Adding linux-rdma folks as that
> is where this will eventually target.

Typically in cases like this you'd paravirtualize some of the VF
before sticking it in the VM so that there is a tidy channel between
the VF driver and the VMM to do whatever this coordination is. There
are many examples, but it is hard to see if you don't know the device
architectures in detail.

If you stick it in seperate virtio PCI device you'll have hard
problems co-ordinating the two drivers.

Jason