Allow access of QEMU VMs to port 0x80

May be used by guests unaware of KVM for IO delays.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Add support for xsetbv guest exists

This is required for stable xsave and avx support: xsetbv exits
unconditionally to the hypervisor. Validate the parameters and issue
the instruction on behalf of the cell. xgetbv is not supported yet as it
is not used by Linux.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>