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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Sunday, September 2, 2012, 4:58:58 PM, you wrote:

> On 02/09/2012 09:43, "Sander Eikelenboom" <linux@xxxxxxxxxxxxxx> wrote:

>>> Quite simply, there likely needs to be more tracing on the IOMMU fault path.
>>> That's a separate concern from your keyhandler of course, but just saying
>>> I'd be looking for the former rather than the latter, for diagnosing
>>> Sander's bug.
>> 
>> Are there any printk's I could add to get more relevant info about the 
>> AMD-Vi:
>> IO_PAGE_FAULT ?

> No really straightforward one. I think we need a per-IOMMU-type handler to
> walk the IOMMU page table for a given virtual address, and dump every
> page-table-entry on the path. Like an IOMMU version of show_page_walk().
> Personally I would suspect this is more useful than the dump-everything
> handlers: just give a *full* *detailed* walk for the actually interesting
> virtual address (the one faulted on).

>> I have attached new output from xl dmesg, this time with iommu=debug on (the
>> option changed from 4.1 to 4.2).

> Not easy to glean any more from that, without extra tracing such as
> described above, and/or digging into the guest to find what driver-side
> actions are causing the faults.

OK, too bad!
With xen 4.1 i haven't experienced those page faults, but a diff between 
/xen/drivers/passthrough/amd in both trees show quite some changes :(

>  -- Keir

>> 
>> 
>>>  -- Keir
>> 






-- 
Best regards,
 Sander                            mailto:linux@xxxxxxxxxxxxxx


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