RE: [Xen-ia64-devel] lsapic deliver external IRQ

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Sorry I missed this one... 

> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> > While Xen/ia64 is executing, interrupts are generally enabled
> > (and, indeed, may even nest).  If, while Xen is executing,
> > an interrupt arrives that results in a pending interrupt
> > for the currently active guest domain, the interrupt needs
> > to be immediately delivered/injected.  
> Yes. No problem, that is why I suggest to do interruption 
> injection (or reflection in current implementation term) 
> within vcpu_pend_interrupt.
> > That's why vcpu_pend_interrupt
> > is called when Xen is about to return to the active domain.
> > Without this check it might be a very long time before the
> > guest gets the interrupt.
> No. It will be delivered at 1st time when it can be 
> delivered. The current approach is just polling always to no 
> loss it but my proposal is to want for the event of to be 
> able to deliver.

I see... if you are suggesting that the call to
check_pending_interrupts is expensive and returns "no
interrupt" almost all the time, I fully agree.
This call could/should be changed to just check
the domain's pending_interruption flag.  But I seem
to recall that I tried that and the test failed (probably
the machine froze) so I fell back to the more conservative
call that worked.  Perhaps it is time to try it again.

Dan

_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel