Re: [Xen-devel] iommu=dom0-passthrough behavior

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.11.12 at 07:21, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> wrote:
>> >> Which, if I'm not mistaken, could be implemented entirely independent
>> >> of "iommu=dom0-passthrough". I'll see if that helps on the offending
>> system.
>> >
>> > I mean this one:
>> >>>c) we could provide a command line option to allow fake devices to be
>> >>>create
>> >
>> > Yes,  I don't think "iommu=dom0-passthrough" can meet your requirement.
>> >  We had better add a cmd line option to  pass the related information
>> > to hypervisor and VT-d can create the pass-through context entry  for
>> > the undetectable device.
>> 
>> You misunderstood: What I was saying (and seeking confirmation) is that I
>> don't think the new command line option would need to have any
>> connection to the existing, non-suitable one. In particular, for it to take 
> effect,
>> "iommu=dom0-passthrough"
>> wouldn't need to be specified at all.
> Okay.  Back to your customer's issue, I don't think we have a clean solution 
> if the device can't be detected by hypervisor.   We only can figure out how 
> to workaround this issue through a new command line option.  
> BTW,   if the device can't be detected,  how to load its driver by OS ?  

Once again - the device a function 0 is being detected, but when the
driver loads we see at least on DMA operation with a source ID of
function 1 under the same bus and slot. There's no driver needed for
the phantom device at function 1.

Jan


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