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Re: [Xen-devel] trying to understand interrupts from xen->guest

On Fri, 25 Jun 2004, Keir Fraser wrote:

> > hmm maybe it is calling back to 0 ... that would explain my call frame 
> > completely. 
> Not sure what you mean here. Yes, you could get an interrupt on
> event-channel 0 -- at start of day no event channels are masked, but
> also none are bound to event sources. The only exception is evtchn 0,
> which is statically bound to VIRQ_MISDIRECT. This is a 'dumping
> ground' for any VIRQs that occur that you have not yet bound to an
> event channel.

no, what I mean is, I get a trap which to plan 9 exception handlers 
looks like a page fault and the PC is 0. This could be the variable-sized 
xen stack frame confusing plan 9 trap again, however.

I am worried that xen is calling back to that PC somehow. Seems unlikely 
but it would explain the stack frame I have. 

HOWEVER  ... seems that what you are telling me is that I should expect an 
irq on VIRQ_MISDIRECT, which makes a lot of sense and explains the linux 
code I see. 

So I'll look at that too. 


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