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 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


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