Re: [Xen-devel] [TestDay] Xen crash on boot

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.01.14 at 01:47, Eric Houby <ehouby@xxxxxxxxx> wrote:
> On Thu, 2014-01-23 at 11:16 +0000, Jan Beulich wrote:
>> But you didn't turn on interrupt remapping, or it got forcibly
>> disabled:
>> 
>> [Firmware Bug]: AMD-Vi: No southbridge IOAPIC found
>> AMD-Vi: Disabling interrupt remapping
> 
> If there is not a specific switch required to enable interrupt remapping
> while booting 3.12.7 on bare hardware, then it was forcibly disabled.

Indeed it was - I just looked more closely at that code. Seems like
the default changed at some point after I looked last.

> Would boot logs from xen 4.1.3 be helpful?  If so, they are attached.

No. The global remapping tables approach is insecure, and hence
was a wrong route in any event. We should actually get rid of the
respective command line option rather sooner than later.

>> If
>> the kernel responds to that mentioned firmware bug by forcing
>> interrupt remapping off, maybe we would have to do the same...
> 
> That would be better than xen failing to boot.

But you realize that, following precedents elsewhere in the
IOMMU code, we would disable the IOMMU as a whole rather
than just interrupt remapping.

But yes, looking at the Linux side code, I guess we need to do
so. Would be nice if you could confirm that the system comes up
fine (and hopefully without IOMMU faults) with
"iommu=no-intremap,debug" as well as with "iommu=off".

Jan


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