Description of problem:
On the AMD machine, one of the cpu features 'cr8legacy' show by #virsh capabilities doesn't belong to the host.

Version-Release number of selected component (if applicable):
libvirt-0.8.7-2.el6
qemu-kvm-0.12.1.2-2.129.el6
kernel-2.6.32-99.el6

How reproducible:
always

Steps to Reproduce:
1.run #virsh capabilities to check the cpu feature.
2.look up the features in /proc/cpuinfo
3.
  
Actual results:
cr8legacy feature doesn\'t belong to the host

Expected results:
the features show by #virsh capabilities should find in /proc/cpuinfo

Additional info:
#virsh capabilities
 <capabilities>
 <host>
 <uuid>44454c4c-5800-104b-8046-c6c04f4d3258</uuid>
 <cpu>
 <arch>x86_64</arch>
 <model>Opteron_G3</model>
 <vendor>AMD</vendor>
 <topology sockets=\'1\' cores=\'3\' threads=\'1\'/>
 <feature name=\'osvw\'/>
 <feature name=\'3dnowprefetch\'/>
 <feature name=\'cr8legacy\'/>
 <feature name=\'extapic\'/>
 <feature name=\'cmp_legacy\'/>
 <feature name=\'3dnow\'/>
 <feature name=\'3dnowext\'/>
 <feature name=\'pdpe1gb\'/>
 <feature name=\'fxsr_opt\'/>
 <feature name=\'mmxext\'/>
 <feature name=\'ht\'/>
 <feature name=\'vme\'/>
 </cpu>
 <migration_features>
 <live/>
 <uri_transports>
 <uri_transport>tcp</uri_transport>
 </uri_transports>
 </migration_features>
 <topology>
 <cells num=\'1\'>
 <cell id=\'0\'>
 <cpus num=\'3\'>
 <cpu id=\'0\'/>
 <cpu id=\'1\'/>
 <cpu id=\'2\'/>
 </cpus>
 </cell>
 </cells>
 </topology>
 <secmodel>
 <model>selinux</model>
 <doi>0</doi>
 </secmodel>
 </host>

 <guest>
 <os_type>hvm</os_type>
 <arch name=\'i686\'>
 <wordsize>32</wordsize>
 <emulator>/usr/libexec/qemu-kvm</emulator>
 <machine>rhel6.0.0</machine>
 <machine canonical=\'rhel6.0.0\'>pc</machine>
 <machine>rhel5.5.0</machine>
 <machine>rhel5.4.4</machine>
 <machine>rhel5.4.0</machine>
 <domain type=\'qemu\'>
 </domain>
 <domain type=\'kvm\'>
 <emulator>/usr/libexec/qemu-kvm</emulator>
 </domain>
 </arch>
 <features>
 <cpuselection/>
 <pae/>
 <nonpae/>
 <acpi default=\'on\' toggle=\'yes\'/>
 <apic default=\'on\' toggle=\'no\'/>
 </features>
 </guest>

 <guest>
 <os_type>hvm</os_type>
 <arch name=\'x86_64\'>
 <wordsize>64</wordsize>
 <emulator>/usr/libexec/qemu-kvm</emulator>
 <machine>rhel6.0.0</machine>
 <machine canonical=\'rhel6.0.0\'>pc</machine>
 <machine>rhel5.5.0</machine>
 <machine>rhel5.4.4</machine>
 <machine>rhel5.4.0</machine>
 <domain type=\'qemu\'>
 </domain>
 <domain type=\'kvm\'>
 <emulator>/usr/libexec/qemu-kvm</emulator>
 </domain>
 </arch>
 <features>
 <cpuselection/>
 <acpi default=\'on\' toggle=\'yes\'/>
 <apic default=\'on\' toggle=\'no\'/>
 </features>
 </guest>

</capabilities>


# cat /proc/cpuinfo 
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 15
model		: 107
model name	: AMD Athlon(tm) Dual Core Processor 4450B
stepping	: 2
cpu MHz		: 1000.000
cache size	: 512 KB
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 1
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch lbrv
bogomips	: 2004.44
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc 100mhzsteps

processor	: 1
vendor_id	: AuthenticAMD
cpu family	: 15
model		: 107
model name	: AMD Athlon(tm) Dual Core Processor 4450B
stepping	: 2
cpu MHz		: 1000.000
cache size	: 512 KB
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 1
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch lbrv
bogomips	: 2004.44
TLB size	: 1024 4K pages
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc 100mhzsteps