[Simh] Simh CPU IDLE and Xen

[Lennert Van Alboom]

Hello,

I've been working on a small "appliance-ish" linux installation that
does nothing but boot, bring up the needed devices, and load simh. This
is on VMware server, and it works just peachy (yes! Simh VAX/VMScluster
on two VMs!).

When doing the same on a Xen VM however, the CPU IDLE functionality
doesn't work anymore. Simh takes 100% cpu, which means that a full core
of the host server is eaten. Seeing how this Xen server hosts roughly
100 VMs (or domUs, to use the Xen terminology) on 8 cores, that's a bit
painful.

Xen domUs are paravirtualized, so that may very well be the reason why
it doesn't work - I'm not aware of how exactly Xen does cpu idling for
its domUs. 

Has anyone tried simh/vax on Xen yet, and if yes, is there a trick to
get it to work without dedicating a core to that VM? If no, any hints on
where I could start debugging this? I don't mind digging into the simh
code, but I'd need a pointer at least :-)

Thanks,

Lennert