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[Xen-devel] Re: [PATCH][FIX] Possible fix for spurious interrupts

>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 14.04.06 20:42:18 >>>
>On 14 Apr 2006, at 18:42, Jan Beulich wrote:
>> This looks questionable to me (even after your follow-up mails). You 
>> are, in this mode, ack-ing the interrupt before the
>> handler even gets invoked. I would expect level triggered interrupts 
>> to fire again right away then if you don't manage
>> to run the handling domain before re-enabling interrupts. Of course, I 
>> haven't seen your later attempts at fixing the
>> problem, but am I missing something here?
>Yes, I ack *after* the handlers have executed. The ack is in the ->end 

Oh, I see. I was looking at the patch only (at home), and missed that its main 
change was to the end routine.

>This is dodgy too on Xen unfortunately. All lower priority interrupts 
>are blocked until the driver domain sees fit to tell Xen it's finished 
>ISR processing. But if a large proportion of x86 hardware is screwed 
>with respect to IO-APIC masking then we have no choice but to get this 
>scheme to work. I look forward to the day when MSI is ubiquitous.

... and even worse when the interrupt belongs to a domU.

Have you heard anything from Intel on this? I am still hoping that there is a 
pattern which interrupt gets triggered by
masking a certain other one, so a (perhaps more complex, but less impacting) 
fix could be derived...


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