BTX halted booting freebsd guest from CentOS

[John Hein]

I am trying to install a xen freebsd guest domU running under CentOS.
When virt-install tries to boot a freebsd iso, I get BTX halted
errors (like below).

I've seen some mention that real-mode BTX may fix this.  Those changes
should be in freebsd 7.2, 8.0 and 9.0 iso's.  But they all get 'BTX
halted' (as does 6.4).


int=0000000d  err=00000000  efl=00010046  eip=000090e8
eax=00050033  ebx=00042820  ecx=00000000  edx=0000a000
esi=00209601  edi=00005f98  ebp=00000000  esp=746e690a
cs=0008  ds=0000  es=0000   fs=0000  gs=0000  ss=0010
cs:eip=0f 01 15 d0 95 00 00 66-ea f5 90 18 00 b1 20 8e
       d1 8e d9 8e c1 8e e1 8e-e9 48 0f 22 c0 ea 0a 91
ss:esp=ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff
       ff ff ff ff ff ff ff ff-ff ff ff ff ff ff ff ff
BTX halted