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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.11.14 at 16:48, <david.vrabel@xxxxxxxxxx> wrote:
> On 21/11/14 15:38, Jan Beulich wrote:
>>>>> On 21.11.14 at 16:01, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> On 21/11/14 14:54, Jan Beulich wrote:
>>>>>>> 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?
>>>
>>> It is wider than 44 bits, so doesn't fit in a 32bit pfn for p2m/m2p
>>> update operations.
>> 
>> MMIO regions don't go into these tables.
> 
> They do in upstream kernels.

Which still is no reason to make the hypervisor or tools refuse
anything here. A check like the one JÃrgen is asking for should
be added only if something in the public interface prevents this
from working; everything beyond should be dealt with by the
respective kernel.

Jan

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