KVM: introduce KVM_ERR_PTR_BAD_PAGE

It is used to eliminate the overload of function call and cleanup
the code

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index eb73e5f..93d3c6e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -922,17 +922,6 @@
 }
 EXPORT_SYMBOL_GPL(kvm_disable_largepages);
 
-int is_error_page(struct page *page)
-{
-	return IS_ERR(page);
-}
-EXPORT_SYMBOL_GPL(is_error_page);
-
-struct page *get_bad_page(void)
-{
-	return ERR_PTR(-ENOENT);
-}
-
 static inline unsigned long bad_hva(void)
 {
 	return PAGE_OFFSET;
@@ -1179,7 +1168,7 @@
 	WARN_ON(kvm_is_mmio_pfn(pfn));
 
 	if (is_error_pfn(pfn) || kvm_is_mmio_pfn(pfn))
-		return get_bad_page();
+		return KVM_ERR_PTR_BAD_PAGE;
 
 	return pfn_to_page(pfn);
 }