KVM: SVM: Add VMRUN handler

KVM: SVM: Add VMRUN handler

This patch implements VMRUN. VMRUN enters a virtual CPU and runs that
in the same context as the normal guest CPU would run.
So basically it is implemented the same way, a normal CPU would do it.

We also prepare all intercepts that get OR'ed with the original
intercepts, as we do not allow a level 2 guest to be intercepted less
than the first level guest.

v2 implements the following improvements:

- fixes the CPL check
- does not allocate iopm when not used
- remembers the host's IF in the HIF bit in the hflags

v3:

- make use of the new permission checking
- add support for V_INTR_MASKING_MASK

v4:

- use host page backed hsave

v5:

- remove IOPM merging code

v6:

- save cr4 so PAE l1 guests work

v7:

- return 0 on vmrun so we check the MSRs too
- fix MSR check to use the correct variable

Acked-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>