With KVM, Processor, Configuration, Model -> Copy host CPU configuration 
= Opteron_G3
-> no illegal instructions
initial tested only 30 minutes : it does seem to work - no indept testing yet

cat /proc/cpuinfo 
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 16
model		: 2
model name	: AMD Phenom(tm) 9550 Quad-Core Processor
stepping	: 3
cpu MHz		: 1497.506
cache size	: 512 KB
fpu		: yes
fpu_exception	: yes
cpuid level	: 5
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt pdpe1gb lm up rep_good extd_apicid unfair_spinlock pni cx16 popcnt hypervisor lahf_lm cmp_legacy svm cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw npt
bogomips	: 2995.01
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

-----------------------------------------------------------------
With KVM, Processor, Configuration, Model 
default settings (blanc)

works up to asterisk1.8.12.X
does no longer work from 1.8.13.X onwards

cat /proc/cpuinfo 
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 6
model		: 2
model name	: QEMU Virtual CPU version 0.15.1
stepping	: 3
cpu MHz		: 1497.506
cache size	: 512 KB
fpu		: yes
fpu_exception	: yes
cpuid level	: 4
wp		: yes
flags		: fpu de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm up unfair_spinlock pni cx16 popcnt hypervisor lahf_lm svm abm sse4a
bogomips	: 2995.01
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: