KVM: MMU: Add infrastructure for two-level page walker

This patch introduces a mmu-callback to translate gpa
addresses in the walk_addr code. This is later used to
translate l2_gpa addresses into l1_gpa addresses.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f2ecdd5..917e68f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -534,6 +534,11 @@
 	return (gpa_t)gfn << PAGE_SHIFT;
 }
 
+static inline gfn_t gpa_to_gfn(gpa_t gpa)
+{
+	return (gfn_t)(gpa >> PAGE_SHIFT);
+}
+
 static inline hpa_t pfn_to_hpa(pfn_t pfn)
 {
 	return (hpa_t)pfn << PAGE_SHIFT;