[PATCH v8 05/11] xen: grant_table: implement grant_table_warn_active_grants()

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Log first 10 active grants of 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.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 xen/common/grant_table.c      | 31 +++++++++++++++++++++++++++++++
 xen/include/xen/grant_table.h |  5 +++++
 2 files changed, 36 insertions(+)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index db5e5db..c67db28 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -3309,6 +3309,37 @@ 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;
+
+    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 <= 10 )
+            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 > 10 )
+        printk(XENLOG_G_DEBUG "Dom%d has too many (%d) active grants"
+               " to report\n", d->domain_id, nr_active);
+
+    read_unlock(&gt->lock);
+}
 
 void
 grant_table_destroy(
diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index 9c7b5a3..54005cc 100644
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -90,6 +90,11 @@ 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(
-- 
2.4.2