Re: [Xen-devel] PCI-passthrough for 32 bit guests and high MMIO addresses

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.11.14 at 15:39, <JGross@xxxxxxxx> wrote:
> Trying to do PCI-passthrough with a 32-bit pv-domain I passed the
> wrong device to the domain. The MMIO address was too large for a
> MFN of a 32-bit system (it was 380003200000-3800036fffff).
> 
> Instead of rejecting the operation Xen tried to perform it resulting
> in a (quite understandable) failure in the domU.
> 
> I think either the hypervisor or the tools should refuse to do
> PCI-passthrough in this case.

What's wrong with this large an address? 32-bit PV uses PAE, i.e.
can map them. If the kernel isn't capable of that that's not
something to make Xen (or the tools) refuse such assignments. I
would only see an issue if a hypercall interface involved here isn't
using wide enough fields (but these addresses should be read
from the BARs, i.e. no hypercall involved).

Jan


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