xen/xenbus: let xenbus_map_ring_valloc() return errno values only

Today xenbus_map_ring_valloc() can return either a negative errno
value (-ENOMEM or -EINVAL) or a grant status value. This is a mess as
e.g -ENOMEM and GNTST_eagain have the same numeric value.

Fix that by turning all grant mapping errors into -ENOENT. This is
no problem as all callers of xenbus_map_ring_valloc() only use the
return value to print an error message, and in case of mapping errors
the grant status value has already been printed by __xenbus_map_ring()
before.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200701121638.19840-3-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/xenbus/xenbus_client.c

@@ -456,8 +456,7 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
  * Map @nr_grefs pages of memory into this domain from another
  * domain's grant table.  xenbus_map_ring_valloc allocates @nr_grefs
  * pages of virtual address space, maps the pages to that address, and
- * sets *vaddr to that address.  Returns 0 on success, and GNTST_*
- * (see xen/include/interface/grant_table.h) or -ENOMEM / -EINVAL on
+ * sets *vaddr to that address.  Returns 0 on success, and -errno on
  * error. If an error is returned, device will switch to
  * XenbusStateClosing and the error message will be saved in XenStore.
  */
@@ -477,18 +476,11 @@ int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
 		return -ENOMEM;
 
 	info->node = kzalloc(sizeof(*info->node), GFP_KERNEL);
-	if (!info->node) {
+	if (!info->node)
 		err = -ENOMEM;
-		goto out;
-	}
-
-	err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
-
-	/* Some hypervisors are buggy and can return 1. */
-	if (err > 0)
-		err = GNTST_general_error;
+	else
+		err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
 
- out:
 	kfree(info->node);
 	kfree(info);
 	return err;
@@ -507,7 +499,6 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 			     bool *leaked)
 {
 	int i, j;
-	int err = GNTST_okay;
 
 	if (nr_grefs > XENBUS_MAX_RING_GRANTS)
 		return -EINVAL;
@@ -522,7 +513,6 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 
 	for (i = 0; i < nr_grefs; i++) {
 		if (info->map[i].status != GNTST_okay) {
-			err = info->map[i].status;
 			xenbus_dev_fatal(dev, info->map[i].status,
 					 "mapping in shared page %d from domain %d",
 					 gnt_refs[i], dev->otherend_id);
@@ -531,7 +521,7 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 			handles[i] = info->map[i].handle;
 	}
 
-	return GNTST_okay;
+	return 0;
 
  fail:
 	for (i = j = 0; i < nr_grefs; i++) {
@@ -554,7 +544,7 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 		}
 	}
 
-	return err;
+	return -ENOENT;
 }
 
 /**