KVM: Introduce hva_to_gfn_memslot() for kvm_handle_hva()

This restricts hva handling in mmu code and makes it easier to extend
kvm_handle_hva() so that it can treat a range of addresses later in this
patch series.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/powerpc/kvm/book3s_64_mmu_hv.c

@@ -772,10 +772,10 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
 
 		end = start + (memslot->npages << PAGE_SHIFT);
 		if (hva >= start && hva < end) {
-			gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;
+			gfn_t gfn = hva_to_gfn_memslot(hva, memslot);
+			gfn_t gfn_offset = gfn - memslot->base_gfn;
 
-			ret = handler(kvm, &memslot->rmap[gfn_offset],
-				      memslot->base_gfn + gfn_offset);
+			ret = handler(kvm, &memslot->rmap[gfn_offset], gfn);
 			retval |= ret;
 		}
 	}

arch/x86/kvm/mmu.c

@@ -1278,8 +1278,7 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
 
 		end = start + (memslot->npages << PAGE_SHIFT);
 		if (hva >= start && hva < end) {
-			gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;
-			gfn_t gfn = memslot->base_gfn + gfn_offset;
+			gfn_t gfn = hva_to_gfn_memslot(hva, memslot);
 
 			ret = 0;
 

include/linux/kvm_host.h

@@ -740,6 +740,14 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
 		(base_gfn >> KVM_HPAGE_GFN_SHIFT(level));
 }
 
+static inline gfn_t
+hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot)
+{
+	gfn_t gfn_offset = (hva - slot->userspace_addr) >> PAGE_SHIFT;
+
+	return slot->base_gfn + gfn_offset;
+}
+
 static inline unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot,
 					       gfn_t gfn)
 {