KVM: x86: Add a framework for supporting MSR-based features

KVM: x86: Add a framework for supporting MSR-based features

Provide a new KVM capability that allows bits within MSRs to be recognized
as features.  Two new ioctls are added to the /dev/kvm ioctl routine to
retrieve the list of these MSRs and then retrieve their values. A kvm_x86_ops
callback is used to determine support for the listed MSR-based features.

Signed-off-by: Tom Lendacky <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
[Tweaked documentation. - Radim]
Signed-off-by: Radim Krčmář <[email protected]>