grant_table: implement grant_table_warn_active_grants()

Log first 10 active grants for a domain. This function is going to be used
for soft reset, active grants on this path usually mean misbehaving backends
refusing to release their mappings on shutdown. We need that in addition to
the already existent 'g' keyhandler as such misbehaving backends can cause a
domain to crash right after the soft reset operation and 'g' option won't be
available in this case.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 2b449d56453bcff3de72a14cb70553ff5c513d2e..23185e75370ebb2762c6c3bdb5a3ff3cb24ba5ed 100644 (file)
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -3352,6 +3352,41 @@ gnttab_release_mappings(
     }
 }
 
+void grant_table_warn_active_grants(struct domain *d)
+{
+    struct grant_table *gt = d->grant_table;
+    struct active_grant_entry *act;
+    grant_ref_t ref;
+    unsigned int nr_active = 0;
+
+#define WARN_GRANT_MAX 10
+
+    read_lock(&gt->lock);
+
+    for ( ref = 0; ref != nr_grant_entries(gt); ref++ )
+    {
+        act = active_entry_acquire(gt, ref);
+        if ( !act->pin )
+        {
+            active_entry_release(act);
+            continue;
+        }
+
+        nr_active++;
+        if ( nr_active <= WARN_GRANT_MAX )
+            printk(XENLOG_G_DEBUG "Dom%d has an active grant: GFN: %lx (MFN: %lx)\n",
+                   d->domain_id, act->gfn, act->frame);
+        active_entry_release(act);
+    }
+
+    if ( nr_active > WARN_GRANT_MAX )
+        printk(XENLOG_G_DEBUG "Dom%d has too many (%d) active grants to report\n",
+               d->domain_id, nr_active);
+
+    read_unlock(&gt->lock);
+
+#undef WARN_GRANT_MAX
+}
 
 void
 grant_table_destroy(

diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index 5263fd6e7d7da200ed1147936f35d2da668e3f82..1c29cee80e042d3a5ea5329420beece039adb77b 100644 (file)
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -89,6 +89,11 @@ void grant_table_destroy(
     struct domain *d);
 void grant_table_init_vcpu(struct vcpu *v);
 
+/*
+ * Check if domain has active grants and log first 10 of them.
+ */
+void grant_table_warn_active_grants(struct domain *d);
+
 /* Domain death release of granted mappings of other domains' memory. */
 void
 gnttab_release_mappings(