The following reply was made to PR port-xen/29999; it has been noted by GNATS.

From: Manuel Bouyer <bouyer@antioche.lip6.fr>
To: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>
Cc: gnats-bugs@NetBSD.org, port-xen-maintainer@NetBSD.org,
	gnats-admin@NetBSD.org, netbsd-bugs@NetBSD.org
Subject: Re: port-xen/29999: ctrl_if_interrupt IPL problem
Date: Tue, 19 Apr 2005 09:04:37 +0200

 On Tue, Apr 19, 2005 at 09:06:57AM +0900, YAMAMOTO Takashi wrote:
 > hi,
 > 
 > > We could move __ctrl_if_tx_tasklet() to run from the softintr. This would
 > > fix the wakeup issue.
 > > For softintr_schedule(), we could probably use IPL_SOFTXENEVT instead of
 > > IPL_SOFTNET, and call ctrl_if_softintr_handler() from the assemby code
 > > instead. This should take care of the issue.
 > 
 > you mean (ab)using softintr() as xenevt does?
 
 Yes
 
 > i think it should work.
 > 
 > (although i'm not entirely happy with how xenevt works,
 > making hacks similar is a good thing :-)
 > 
 > > IPL_CTRL needs to be very high because the console I/O is done though
 > > control messages on guest domains, and there's no way to poll for keyboard
 > > input. So, to get ddb working in guest domains, we need to have control
 > > events enabled while in ddb.
 > 
 > "keyboard input" meant "console input"?
 
 Yes, sorry for the bad wordings here
 
 > 
 > > I guess we could also be busy-looping waiting for the event, but it
 > > would not be nice to other guests domains.
 > 
 > if there's a way to poll events (i couldn't find any),
 > i think it's better to use it because ddb needs to do busy-loop anyway.
 
 Not here, xenconscn_getc() calls HYPERVISOR_yield() when it waits for
 input, so it won't consume CPU. But HYPERVISOR_yield() won't return unless
 interrupts are enabled.
 
 -- 
 Manuel Bouyer <bouyer@antioche.eu.org>
      NetBSD: 26 ans d'experience feront toujours la difference
 --