Re: [Xen-devel] Lenovo T400 problem

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Mar 10, 2010 at 02:56:48PM +0200, Tom Rotenberg wrote:
> Hi all,
> Environment:
> I'm trying to run T400 with USB and WLAN assigned to my HVM (Windows
> XP). I'm using XEN 3.4 19696 changeset.


> 
> Facts:
> Running both of them together stuck my machine in Windows splash
> screen with following output:
> 
> (XEN) [VT-D]iommu.c:694: iommu_fault:DMA Read: 0:3.7 addr 6cb6000


What device is under BDF: 0:3.7 ?
> REASON 2 iommu->reg = ffff828bfff57000


Hmm.. you really need the secret key decoder to figure that one out.
I think it is 'Present bit in context entry is clear"'

Looking at 
"http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf
 "
it says:

"Present Flag: The present field is used by software to indicate to
hardware whether the contextentry
is present and initialized. Software may Clear the present field for
context entries
corresponding to device functions that are not present in the platform.
If the present field of a
context-entry used to process a DMA request is Clear, the DMA request is
blocked, resulting in a
translation fault."


So from reading that it seems that the device in question: 0:3:7 hasn't
been actually authorized for to be used by your guest?



> (XEN) print_vtd_entries: iommu = ffff83013bdf5f90 bdf = 0:3:7 gmfn = 6cb6
> (XEN)     root_entry = ffff83013bdcc000
> (XEN)     root_entry[0] = 137e44001
> (XEN)     context = ffff830137e44000
> (XEN)     context[1f] = 0_0
> (XEN)     ctxt_entry[1f] not present

Sure enought. Not present it there.. Are there any other entries
(earlier on) that talk about BDF 0:3:7?


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