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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.11.14 at 16:07, <furryfuttock@xxxxxxxxx> wrote:
> Thanks Jan,
> 
> Thursday, November 13, 2014, 11:08:33 AM, you wrote:
> 
>>>>> On 13.11.14 at 14:29, <furryfuttock@xxxxxxxxx> wrote:
>>> I am having 2 major problems at the moment.
>>> 
>>> 1.- Access to the PCI device from the PV will fail the second time I
>>> create it UNLESS I call xl pci-assignable-remove/pci-assignable-add
>>> between each creation. If I don't do this then all PCI accesses return
>>> -1. I get the same if I disable memory access in the PCI configuration
>>> register.
>>> 
>>> 1.1.- Is this expected behaviour?
> 
>> No. But did you verify the driver properly enables the device (i.e.
>> doesn't make assumptions on its state)? Also iirc some kernel
>> versions weren't properly resetting the device when coming back
>> from guest use, but without you stating the software versions
>> you're using that's just a remote possibility.
> 
> 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...

> 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?

Jan



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