I'm getting close to disabling SELinux under F10. I'm trying to setup a bridged network so that my windows guest can have full access to the network. Windows runs fine in qemu_kvm using the "-net nic -net user" options. My problem is that in bridge mode it uses "-net nic,macaddr=11:22:33:44:55:66 -net tap". When I try to run the virtual machine I get this message "warning: could not configure /dev/net/tun: no virtual network emulation".
Update: I disabled SELinux, but that didn't fix the problem. I got rid of the error by configuring the tap at least somewhat correctly. I still can't get the bridge to work.
Update: My virtual machines now work with bridged networking. The MAC address that I created above doesn't work. You need to make it something else. Use the networking information on this page as a guide to setting it up. I'm using the /etc/qemu-ifup. I use this script to create 3 taps corresponding to three virtual machines so I can run them at the same time. I don't let my scripts for the virtual machine startup run the /etc/qemu-ifup script. If you're running SELinux make sure that you apply the proper labels to the image.
I'm running a machine with 8GBs of RAM on an AMD Phenom II 840 processor. I'm getting good performance with it. I did upgrage the Fedora 10 kvm module to one from Fedora 11 development repos so that it wouldn't have so many problems with audio.