FreeBSD 10-R 8 vCPU panics at boot under XenServer (on 8 'core' CPU)

[Karl Pielorz]

Hi,

I've got a FreeBSD 10-R amd64 DomU guest I'm using under XenServer 6.2 
(SP1) - this was working fine (i.e. had been restarted many times - while I 
look at things like HAST).

I noticed the other day it was only set to use 4 vCPU's - so I increased 
this to 8 (the machine has an 4 Core, 8 Thread Xeon 1230v3 in it - which 
Xen see's as 8 CPU cores).

However, it won't boot reliably now:

"
...
SMP: AP CPU #5 Launched
panic: can't schedule timer
cpuid = 0
KDB: stack backtrace:
#0 0xffffffff808e7dd0 at kdb_backtrace+0x60
#1 0xffffffff808af8b5 at panic+0x155
#2 0xffffffff807a14dd at xentimer_et_start+0xed
#3 0xffffffff80d66d6d at loadtimer+0xfd
#4 0xffffffff80d657fd at handleevents+0x308
#5 0xffffffff80d65fc8 at timercb+0x308
#6 0xffffffff807a152d at xentimer_intr+0x4d
#7 0xffffffff80883e5b at intr_event_handle+0x9b
...
"

Less than 8 vCPU's seems to boot OK (e.g. 7) and 8 vCPU's has booted a 
couple of times (out of 30+ reboots).

The system is running GENERIC with:

  options   NO_ADAPTIVE_MUTEXES
  options   NO_ADAPTIVE_RWLOCKS
  options   NO_ADAPTIVE_SX

In addition XenServer is set to pass through the bare machine's LSI and two 
Intel NIC's (which it does - and are working, once FreeBSD is booted).

Any idea's?

-Karl