Re: DMA support via gb-netlink and gbridge

[Kyle Harding <kyle@xxxxxxxxx>]

Thanks Greg, I've explained our solution poorly so I'll quote a colleague as I'm too close to the problem at this point!

We'd like to essentially run a virtualized vendor kernel to manage a hardware device such as an SDIO wireless card passed through from the host, running a mainline kernel. Network traffic would be routed from host to guest over a virtio interface.

Is it possible to use Greybus in this way, or am I misunderstanding the use case of this subsystem?

On Mon, Apr 19, 2021 at 3:38 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:

On Sun, Apr 18, 2021 at 01:31:23PM -0400, Kyle Harding wrote:
> That does help, thank you Greg! It seems that in general the transport
> shouldn't be a problem.
>
> What if the non-hardware side is a kvm guest kernel without IOMMU support?
> If we used greybus to expose the SDIO bus to the kvm would the DMA transfer
> garbage in Host Memory?
>
> I understand this is a non-traditional approach, and I believe that with
> IOMMU this wouldn't be an issue.

Again, I think you are getting very confused as to what the greybus
protocol stack is for.

You can use it for any type of bus you want, you just need to write a
driver for that transport layer.  But for talking to virtual machines,
why not just use the virtio layer which is designed just for that?  You
could make a virtio transport for greybus, but really, why?  Who would
use that?

And again, IOMMUs have nothing to do with this at all.

thanks,

greg k-h

_______________________________________________
greybus-dev mailing list
greybus-dev@xxxxxxxxxxxxxxxx
https://lists.linaro.org/mailman/listinfo/greybus-dev