KVM: SVM: Implement hsave

Implement the hsave MSR, that gives the VCPU a GPA to save the
old guest state in.

v2 allows userspace to save/restore hsave
v4 dummys out the hsave MSR, so we use a host page
v6 remembers the guest's hsave and exports the MSR

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

arch/x86/kvm/kvm_svm.h

@@ -41,6 +41,8 @@ struct vcpu_svm {
 	unsigned long host_dr7;
 
 	u32 *msrpm;
+	struct vmcb *hsave;
+	u64 hsave_msr;
 };
 
 #endif