Re: [Xen-devel] Using debug-key 'o: Dump IOMMU p2m table, locks up machine

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.09.12 at 12:48, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:

> Wednesday, September 5, 2012, 12:40:31 PM, you wrote:
> 
>>>>> On 05.09.12 at 12:25, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:
>>> Wednesday, September 5, 2012, 12:14:02 PM, you wrote:
>>>>>>> On 04.09.12 at 18:43, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:
>>>>> ...........................<0>AMD-Vi: IO_PAGE_FAULT: domain = 0, device 
>>>>> id = 
>>>>> 0x0a06, fault address = 0xc2c2c2c0
>>> 
>>>> Looks like use of uninitialized memory (assuming you're using a
>>>> debug hypervisor, that's the pattern scrub_one_page() puts
>>>> there). But it's unclear to me what device should be doing any
>>>> I/O at that point (and even if one does, how it would get the
>>>> bad address loaded). What is 0a:00.6?
>>> 
>>> since 4.2-rc4 is still unstable it has debug=y for what i know, so yes.
>>> This particular IO_PAGE_FAULT happened before the kernel loads, so the 
>>> kernel and pciback shouldn't be causing the issue one would say.
>>> With pciback i'm hiding 03:06.0, 04:00.*, 05:00.0, 0a:00.* and 07:00.0 at 
>>> boot.
>>> 
>>> Is there any code i could add to get more info where it comes from ?
> 
>> Hardly, since those accesses are asynchronous to what the CPUs
>> do. But ...
> 
>>> 0a:00.6 USB controller: NetMos Technology MCS9990 PCIe to 4ÃPort USB 2.0 
> Host Controller
> 
>> ... are your keyboard/mouse perhaps connected to this one? In
>> which case I'd suppose the 1:1 tables set up for Dom0 might not
>> be complete. Wei?
> 
> Nope this machine is running without any keyboard/mouse, the USB controller 
> at present has only one device connected to it:
> in the pv guest lsusb:
> Bus 007 Device 002: ID 10cf:5500 Velleman Components, Inc. 8055 Experiment 
> Interface Board (address=0)

And this is not by chance hanging off the controller that the fault
was reported for?

> And as i said, the hardware didn't change between my switch from xen-4.1.3 
> to xen-4.2.

I understand that, but the problem here showed up only after
toggling the page table sharing option iirc.

Jan

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