probing EDD boot message stays for ten minutes on centos 6.6

I had the same symptoms but the problem was that the vmware console wasn't showing the boot output (after the EDD line and a few minutes, the login prompt suddelny appeared) I added

console=tty0 console=ttyS0,115200

..to the grub and next boot all was fine

You don't have to set this in virt-manager.

Add edd=off to the first(!) kernel line inside the VM in /boot/grub/grub.conf, e.g. like so:

kernel /vmlinuz-2.6.32-504.1.3.el6.x86_64 ro root=/dev/mapper/vg01-lv_root rd_LVM_LV=vg01/lv_swap rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg01/lv_root  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet edd=off

I say only to the first line as you can then use an alternative menu entry if this creates problems, and also because the options used in this line will also be used for newer kernels installed by updates.

For a first test, you can also connect to the VM console, either with virt-manager or a VNC client and press e for edit in the Grub boot menu and then add this option to the kernel command line.