Re: [Xen-devel] Sharing MMIO page with DomU on a system with no IOMMU

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.10.12 at 09:19, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2012-10-16 at 08:08 +0100, Jan Beulich wrote:
>> >>> On 15.10.12 at 18:50, Martin Roth <gaumless@xxxxxxxxx> wrote:
>> > 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.
>> 
>> Looks like you have to assign the PCI device providing the GPIOs
>> to the guest, as there doesn't currently appear to be a way to
>> allow guest access to individual MMIO pages (lacking the MMIO
>> counterpart to the iports= and irqs= domain config settings).
>> 
>> Ian, Ian - am I overlooking something?
> 
> iomem= support was committed to xl in xen-unstable last week or the week
> before. I think it already existed in xend.

I fail to spot anything like that in xend - the only use of
domain_iomem_permission() is in server\pciif.py afaics.

Jan



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