Re: [Xen-devel] [PATCH 1/2 v5] iommu/amd: Fix logic for clearing the IOMMU interrupt bits

[Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>]

On 6/12/2013 5:37 PM, Suravee Suthikulpanit wrote:
> On 6/12/2013 1:24 AM, Jan Beulich wrote:
> > > If more entries are added to the event log during the time that event
> > > log interrupt is disabled (in the control register),
> > > the IOMMU hardware will generate interrupt once the the interrupt 
> > > enable
> > > bit in the control register changes from 0 to 1 and set the status
> > > register.  Since the "iommu_interrupt_handler" code is already calling
> > > "schedule_tasklet",  we should not need to "re-schedule" tasklet here.
> > > I have confirmed the hardware behavior described with the hardware
> > > designer.  This is also the same on the PPR log.
> > And also the same between v1 and v2 hardware? Again, I'd like to
> > be on the safe side, and rather do a reschedule too much than one
> > too little. And in any case, having your documentation made more
> > precise in these respects would be much appreciated.
> >
> > Jan
> Understand.  I apologize if the AMD IOMMU specification does not 
> describe the behavior quite clearly.  Let me know if I could help 
> clarifing any issues with the hardware designers.
> Since we are modifying the IOMMU interrupt enabling/disabling, I have 
> been doing some more testing on the IOMMU interrupt handling. I found 
> that IOMMU MSI interrupt is currently broken, but I think this is 
> because of some older changes.  I am still tracking down the issue, 
> and will update my findings.
> Thank you,
>
> Suravee
The following commit broke the IOMMU MSI interrupt:

2012-11-28    899110e3f6d2a191638e8b50a981c551eeec49e6 AMD IOMMU: 
include IOMMU interrupt information in 'M' debug key output
(http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=899110e3f6d2a191638e8b50a981c551eeec49e6)

This patch also need the following patch to resolve kernel panic:

c759fee45bf44f2947a3480d54c03ff7e028c39e AMD IOMMU: add locking missing 
from c/s 26198:ba90ecb0231f
(http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=c759fee45bf44f2947a3480d54c03ff7e028c39e)

I'll update once I root cause the issue.

Suravee

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