Re: [Xen-devel] Dealing with non-existent BDF devices in VT-d and in the hardware.

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Konrad Rzeszutek Wilk wrote on 2014-03-18:
> On Mon, Mar 17, 2014 at 01:03:00AM +0000, Zhang, Yang Z wrote:
>> Konrad Rzeszutek Wilk wrote on 2014-03-15:
>>>> 
>>>> What happens if you assign the devices under bus 09 to another guest?
>>> 
>>> Hadn't tried that. I think it would all blow up as the the
>>> non-existent bridge is now assigned to one guest and the phantom
>>> DMA requests for the
>>> 09 would show up under the 08 device. I think I would corrupt the
>>> guest memory with random DMA writes.
>>> 
>>>> Is it better to add Xen command line to add such devices to a
>>>> group and
>>> assign the whole group to a guest when trying to assign a device
>>> of the group to guest?
>>> 
>>> Or implement the group assigment in QEMU or libxl so that nobody
>>> tries doing it.
>> 
>> But I think user still need to tell which device is buggy manually
>> and I don't
> think QEMU or libxl can do it.
> 
> I think there are two issues here:
> 
> a) Missing device assigments via groups. That should be done irregardless
>    if the device / hardware is buggy.
>

Yes, this is missing.

> b) Buggy devices like the IDT bridge that I see. That is a seperate issue - 
> and
>    we just discussion if we want to inject that in the VT-d (or AMD-VI) what
>    would be the mechanism to do that.

The question is that device 08:00.0 doesn't exist in your platform, you only 
saw the BDF in the DMA transaction. How can you add a non-exist device to a 
group? 

>> 
>> Best regards,
>> Yang
>> 
>>


Best regards,
Yang


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