There should be some mechanism by which one can change the cpu model, and thus the cpuid flags as reported within the guest. At present one is limited to exactly 2 cpu models, one for 32 bit and one for 64-bit. Editing this field should not require creation of a new virtual machine, as is currently the case for switching between 32-bit and 64-bit emulation.
-- Fedora Bugzappers volunteer triage team https://fedoraproject.org/wiki/BugZappers
CPU model is now configurable upstream (and does not require creating a new guest): http://hg.fedorahosted.org/hg/virt-manager/rev/2da86617fb68
This is unlikely to be backported to f13, moving to f14.
virt-manager-0.8.7-1.fc14 has been submitted as an update for Fedora 14. https://admin.fedoraproject.org/updates/virt-manager-0.8.7-1.fc14
Package virt-manager-0.8.7-1.fc14: * should fix your issue, * was pushed to the Fedora 14 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing virt-manager-0.8.7-1.fc14' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/virt-manager-0.8.7-1.fc14 then log in and leave karma (feedback).
virt-manager-0.8.7-2.fc14 has been submitted as an update for Fedora 14. https://admin.fedoraproject.org/updates/virt-manager-0.8.7-2.fc14
virt-manager-0.8.7-2.fc14 has been pushed to the Fedora 14 stable repository. If problems still persist, please make note of it in this bug report.