xen: issue warning message when out of grant maptrack entries

When a driver domain (e.g. dom0) is running out of maptrack entries it
can't map any more foreign domain pages. Instead of silently stalling
the affected domUs issue a rate limited warning in this case in order
to make it easier to detect that situation.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

1 files changed, 21 insertions, 6 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 7bafa703a992..84575baceebc 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -1040,18 +1040,33 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                 return ret;
 
         for (i = 0; i < count; i++) {
-                /* Retry eagain maps */
-                if (map_ops[i].status == GNTST_eagain)
-                        gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
-                                                &map_ops[i].status, __func__);
-
-                if (map_ops[i].status == GNTST_okay) {
+                switch (map_ops[i].status) {
+                case GNTST_okay:
+                {
                         struct xen_page_foreign *foreign;
 
                         SetPageForeign(pages[i]);
                         foreign = xen_page_foreign(pages[i]);
                         foreign->domid = map_ops[i].dom;
                         foreign->gref = map_ops[i].ref;
+                        break;
+                }
+
+                case GNTST_no_device_space:
+                        pr_warn_ratelimited("maptrack limit reached, can't map all guest pages\n");
+                        break;
+
+                case GNTST_eagain:
+                        /* Retry eagain maps */
+                        gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref,
+                                                map_ops + i,
+                                                &map_ops[i].status, __func__);
+                        /* Test status in next loop iteration. */
+                        i--;
+                        break;
+
+                default:
+                        break;
                 }
         }