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Re: [Xen-devel] Problems accessing passthrough PCI device



>>> On 13.11.14 at 18:49, <furryfuttock@xxxxxxxxx> wrote:
>>> Yes,  the  first thing I do in the driver is set the PCI configuration
>>> access  bits to 7 that should enable IO space, Memory Space and Master
>>> BUS access.
>>> 
>>> As  a  test I disabled this and all reads to the PCI device return -1,
>>> even the first one.
> 
>> I implied your earlier statement to mean that. But - did you also
>> verify that the three flags actually end up set (ideally from both
>> DomU and Dom0 perspective)? The PCI backend may be screwing
>> up things...
> 
> Yes I do verify the write. How do I check this from Dom0?

Just use lspci.

>>> I  agree,  this looks more than a hang than a crash. I've just found a
>>> link to the USB debug cable. I've ordered one but it will take a while
> 
>> And I hope you first verified that your system meets the criteria
>> for this to work in the first place?
> 
> I followed the checks in the Kernel earlyprintk debugging HOWTO, i.e.
> lspci -vvv to check the USB debug capability, and it verified. The
> device is ordered and now just to wait....

As said before, the less obvious thing to verify is that there must not
be a (hidden) hub in between for the port that can be used as the
debug one. Some systems (I actually have at least one of that kind)
surface some or all of their USB port via some internal hub; lsusb
should be able to tell you. Anyway - you'll see whether it works when
the device arrives.

Jan


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