[libvirt] hvm/x86_64 combination not allowed

[Steve Brown]

>> $ sudo virsh capabilities
>> <capabilities>
>>   <host>
>>     <cpu>
>>       <arch>x86_64</arch>
>>     </cpu>
>>     <migration_features>
>>       <live/>
>>       <uri_transports>
>>         <uri_transport>tcp</uri_transport>
>>       </uri_transports>
>>     </migration_features>
>>   </host>
>>   <guest>
>>     <os_type>hvm</os_type>
>>     <arch name='i686'>
>>       <wordsize>32</wordsize>
>>       <emulator>/usr/bin/qemu</emulator>
>>       <machine>pc-0.11</machine>
>>       <machine canonical='pc-0.11'>pc</machine>
>>       <machine>pc-0.10</machine>
>>       <machine>isapc</machine>
>>       <domain type='qemu'>
>>       </domain>
>>     </arch>
>>     <features>
>>       <pae/>
>>       <nonpae/>
>>       <acpi default='on' toggle='yes'/>
>>       <apic default='on' toggle='no'/>
>>     </features>
>>   </guest>
>> </capabilities>
>
> Ok, this confirms your host OS is x86_64, but it only shows a single
> guest entry for i386. This is because the 'qemu' binar is the 32-bit
> emulator. To make x86_64 guests work, you need to install the
> qemu-system-x86_64 binary, or a KVM binary called 'kvm' or 'qemu-kvm'.
>
> Once those are installed, you should see another <guest> appear in
> that capabilities XML

Unfortunately, I already have the 64bit emulator installed:

$ which qemu-system-x86_64
/usr/local/bin/qemu-system-x86_64
$ ls -l /usr/local/bin/qemu-*
-rwxr-xr-x 1 root root  217184 Jan 14 14:00 /usr/local/bin/qemu-img
-rwxr-xr-x 1 root root  229120 Jan 14 14:00 /usr/local/bin/qemu-io
-rwxr-xr-x 1 root root  210968 Jan 14 14:00 /usr/local/bin/qemu-nbd
-rwxr-xr-x 1 root root 2323328 Jan 14 14:01 /usr/local/bin/qemu-system-x86_64

This was done by building the qemu-kvm-0.12.1.1 package from source.
I am able to run this vm just fine using the qemu-system-x86_64
binary.  I've tried rebuilding libvirt several times to make it aware
that the proper binaries are installed, but it can't seem to find them
for some reason.