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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/11/14 14:39, Juergen Gross wrote:
> Hi,
>
> again a fallout from my "linear p2m list" tests:
>
> 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 actually goes wrong?  Does the 32bit guest truncate the MMIO region
to 44 bits and try to map that?

I would completely agree that something (libxl?) should refuse this
attempt to do passthrough, but I think pci-front should also kick up a
fuss if it is able to detect this error.

~Andrew

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