Re: iommu=0 leading to panic when system defaults to using x2apic

[Yinghai Lu <yinghai@kernel.org>]

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On 12/14/2010 09:08 AM, Jan Beulich wrote:
>>>> On 14.12.10 at 17:53, "Kay, Allen M" <allen.m.kay@intel.com> wrote:
>>>  And why is it that Xen panics when the BIOS pre-enabled x2apic
>>> mode without also enabling interrupt re-mapping, while Linux
>>> (afaict from looking at 2.6.32 code and output from an affected
>>> machine) simply enables interrupt re-mapping in this case?
>>
>> AFAIK, Linux also requires interrupt remapping for x2apic.  I believe 
>> Weidong has fixed the panic issue in Xen when x2apic is enabled without 
>> enabling interrupt remapping.  It should now behave the same way as Linux.
> 
> Oh, and I should have added that I'm currently polishing up
> patches from Yinghai Lu to address this as well as other
> problems preventing (certain?) large boxes from booting or
> functioning correctly.

Yes, just want to make xen aligned to current Linux kernel behavior.
BIOS guys said why Linux non-xen kernel is happy but xen kernel is not.

please check attached patches. Our big box with x2apic-preenabled, AND half cpus' apic id are above 255.

They are on top of xen-4.0.1. and first one is from Weidong in unstable.

Thanks

Yinghai Lu


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