KVM: introduce KVM_PFN_ERR_HWPOISON

Then, get_hwpoison_pfn and is_hwpoison_pfn can be removed

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 ef04916..7fce2d5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -939,17 +939,6 @@
 	return -ENOENT;
 }
 
-static pfn_t get_hwpoison_pfn(void)
-{
-	return -EHWPOISON;
-}
-
-int is_hwpoison_pfn(pfn_t pfn)
-{
-	return pfn == -EHWPOISON;
-}
-EXPORT_SYMBOL_GPL(is_hwpoison_pfn);
-
 int is_noslot_pfn(pfn_t pfn)
 {
 	return pfn == -ENOENT;
@@ -1115,7 +1104,7 @@
 		if (npages == -EHWPOISON ||
 			(!async && check_user_page_hwpoison(addr))) {
 			up_read(&current->mm->mmap_sem);
-			return get_hwpoison_pfn();
+			return KVM_PFN_ERR_HWPOISON;
 		}
 
 		vma = find_vma_intersection(current->mm, addr, addr+1);