Re: [PATCH] VT-d: improve RMRR validity checking

[Weidong Han <weidong.han@intel.com>]

Alex Williamson wrote:
> On Wed, 2010-03-10 at 10:40 +0800, Weidong Han wrote:
>   
>> Alex Williamson wrote:
>>     
>>> I have a system with what I consider to be a valid DRHD that's getting
>>> tripped up on this patch.  The problem is that the DRHD includes an
>>> IOAPIC scope, where the IOAPIC is not materialized on the PCI bus.  I
>>> think Xen is being overzealous in it's validity checking and that this
>>> is a valid configuration.  What do others think?  Are IOAPICs a
>>> special case that we can allow to be non-existent on the PCI bus?
>>>   
>>>       
>> Yes, IOAPIC can be not pci-discoverable. IOAPICs are only reported in 
>> the "Include_all" DRHD, and our patch won't check if the device is 
>> pci-discoverable or not for the "Include_all" DRHD. So I think the patch 
>> is no problem unless IOAPIC is not included in the "Include_all" DRHD. 
>> Can you post your boot logs?
>>     
>
> Weidong,
>
> That's a very subtle restriction, and I'm not sure how it works in
> practice.  If I have a multi-IOH system, each with VT-d hardware, each
> supporting interrupt remapping, each with one or more IOAPICs below
> them, how can interrupt remapping work if we can only associate an
> IOAPIC with the "include all" DRHD?  I'm confused.  Thanks,
>   
Each IOH will have one "include all" DRHD which reports IOAPICs for each 
IOH.

Regards,
Weidong
> Alex
>
>