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

From: Manuel Bouyer <bouyer@antioche.eu.org>
To: gnats-bugs@NetBSD.org
Cc: port-xen-maintainer@NetBSD.org, gnats-admin@NetBSD.org,
	netbsd-bugs@NetBSD.org
Subject: Re: port-xen/29999: ctrl_if_interrupt IPL problem
Date: Mon, 18 Apr 2005 19:59:59 +0200

 Hi,
 
 On Sun, Apr 17, 2005 at 11:25:00PM +0000, yamt@mwd.biglobe.ne.jp wrote:
 > Architecture: i386
 > Machine: i386
 > >Description:
 > 	ctrl_if_interrupt uses wakeup(9) and softintr_schedule(9) from
 > 	interrupt context with too high IPL.
 
 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.
 
 > >How-To-Repeat:
 > 	code inspection.
 > >Fix:
 > 	the easiest fix is, lower IPL_CTRL to IPL_SCHED (or even lower).
 > 	i'm not sure why IPL_CTRL is that high at the first place.
 
 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.
 I guess we could also be busy-looping waiting for the event, but it
 would not be nice to other guests domains.
 xen/xencons.c also has issues with interrupts level because of this,
 I plan to fix this soon.
 
 -- 
 Manuel Bouyer <bouyer@antioche.eu.org>
      NetBSD: 26 ans d'experience feront toujours la difference
 --