I have a licensed copy of MicroSoft Windows 7 professional installed and running as guest on my Linux server running qemu-kvm. This works just fine.
But I was unable to figure out how to Cut'n'paste text selections from a window of the Win7 VM into X11 or vice versa.
Is this possible? How?
As far as I know this is not yet supported.
When necessary, I work around it by connecting to the Windows VM via RDP (in my case using Remmina, but you can use whatever you like).
VNC has no facility for clipboard passthrough. You might want to try spice, with the proper agents it works quite well.