KVM: MMU: Store shadow page tables as kernel virtual addresses, not physical

Simpifies things a bit.

Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 5e6dac5..fc4a6c1 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -139,7 +139,7 @@
 	gfn_t gfn;
 	union kvm_mmu_page_role role;
 
-	hpa_t page_hpa;
+	u64 *spt;
 	unsigned long slot_bitmap; /* One bit set per slot which has memory
 				    * in this shadow page.
 				    */