Re: [Xen-devel] fooey. no interrupts.

[ron minnich <rminnich@xxxxxxxx>]

On Tue, 10 Aug 2004, Keir Fraser wrote:

> 
> > >  4. The original value of vcpu_data[0].evtchn_upcall_pending must be zero.
> > >  5. The value of vcpu_data[0].evtchn_upcall_mask must be zero.
> > 
> > OK, this I don't totally see. From the code I posted before, it seems to 
> > me only the first three conditions matter. 
> 
> The first three conditions cause us to decide whether or not to
> schedule the target domain, sending a cross-cpu interrupt if
> necessary. The final two are checks just before calling back to the
> guest OS, just to check whether it is in a position to receive async
> callbacks. 

Keir, I don't see that in the code and Christian sent a note that left me 
thinking it does not work that way. 

as Christian said, (4) doesn't do anything conditional, it does this:
        /* The VCPU pending flag must be set /after/ update to 
evtchn-pend. */
        s->vcpu_data[0].evtchn_upcall_pending = 1;
        guest_async_callback(d);

which looks pretty unconditional to me. Is there something else I'm 
missing?

thanks

ron


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