netbsd PVH dom0: xen clock event stops

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

Hello,
I spent some more time debugging NetBSD as a PVH dom0 on Xen,
With Roger's patch to avoid a Xen panic, the NetBSD kernel stalls
configuring devices. At first I though it was an issue with hardware
interrupts, but it more likely is an issue with Xen timer events.
Specifically: virtual CPU 0 stops receiving timer events, while other
CPUs keep receiving them. I tried to force a timer rearm but this didn't help.
The event is not masked nor pending on Xen or NetBSD, as confirmed by 'q'.
Others events (the Xen console, the debug event) are properly received
by CPU0. I don't know how to debug this more at this point.

In case it helps, I put by Xen and netbsd kernels at
http://www-soc.lip6.fr/~bouyer/netbsd-dom0-pvh/
I boot it from the NetBSD boot loader with:
menu=Boot Xen PVH:load /netbsd-test console=com0 root=dk0 -vx; multiboot 
/xen-test.gz dom0_mem=1024M console=com2 com2=57600,8n1 loglvl=all 
guest_loglvl=all gnttab_max_nr_frames=64 dom0=pvh iommu=debug

I guess with grub this would be
kernel /xen-test.gz dom0_mem=1024M console=com2 com2=57600,8n1 loglvl=all 
guest_loglvl=all gnttab_max_nr_frames=64 dom0=pvh iommu=debug
module /netbsd-test console=com0 root=dk0 -vx

(yes, com2 for xen and com0 for netbsd, that's not a bug :)
You can enter the NetBSD debugger with
+++++
you can then enter commands, lile
sh ev /i
to see the interrupt counters

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--