Sharing MMIO page with DomU on a system with no IOMMU

[Martin Roth <gaumless@gmail.com>]

Hi -
I'm trying to share an MMIO page from Dom0 running linux with a DomU 
running an RTOS so that I can access the GPIO registers directly. The 
system I need to get this working on does not have an IOMMU. I'm aware 
of the security issues of sharing this area, but don't believe it's an 
issue in this case.  I've got a Linux module set up and can share memory 
between the two domains using the grant table, but I haven't been able 
to get this to work for the MMIO page.

Can anyone give me a pointer on how I should go about doing this?  I 
need the area to actually be shared between both domains, not simply 
owned by the RTOS.


Thanks.
Martin Roth