[Xen-devel] [PATCH v2] xen: issue warning message when out of grant maptrack entries

[Juergen Gross <jgross@xxxxxxxx>]

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@xxxxxxxx>
---
 drivers/xen/grant-table.c | 27 +++++++++++++++++++++------
 1 file 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;
                }
        }
 
-- 
2.16.4


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