Re: [PATCH] libxl: arm: Allow grant mappings for backends running on Dom0

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

On 09-05-23, 16:05, Anthony PERARD wrote:
> I guess the way virtio devices are implemented in libxl suggest to me
> that the are just Xen PV devices. So I guess some documentation in the
> tree would be useful, maybe some comments in libxl_virtio.c.

Our use case is just PV devices, not sure if someone else may want to
use it differently.

I will add the comment.

> > The eventual fronend drivers (like drivers/i2c/busses/i2c-virtio.c)
> > aren't Xen aware and the respective virtio protocol doesn't talk about
> > how memory is mapped for the guest. The guest kernel allows both
> > memory mapping models and the decision is made based on the presence
> > or absence of the iommu node in the DT.
> 
> So, virtio's frontend don't know about xenstore?

Right.

> In this case, there's
> no need to have all those nodes in xenstore under the frontend path.

Yeah, I ended up copying them from disk or kbd I guess, but I am not
using them for sure.

> I guess the nodes for the backends are at least somewhat useful for
> libxl to reload the configuration of the virtio device. But even that
> isn't probably useful if we can't hot-plug or hot-unplug virtio devices.
> 
> Are the xenstore node for the backend actually been used by a virtio
> backend?

Yes, I am using them on the backend side to read device information
whenever a new guest comes in with a bunch of devices.

-- 
viresh