rcu_lock(current->domain) does not need to disable preemption.

If the guest sleeps in hypervisor context, it should not be destroyed
until execution reaches a safe point (i.e., guest context). This is
not implemented yet. :-) But the next patch will rely on it, to allow
an HVM guest to execute hypercalls that indirectly invoke __hvm_copy()
within an rcu_lock_current_domain() region.

Signed-off-by: Keir Fraser <keir@xen.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 1a08636756..803c640a7f 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -398,7 +398,7 @@ struct domain *get_domain_by_id(domid_t dom)
 
 struct domain *rcu_lock_domain_by_id(domid_t dom)
 {
-    struct domain *d;
+    struct domain *d = NULL;
 
     rcu_read_lock(&domlist_read_lock);
 
@@ -407,12 +407,15 @@ struct domain *rcu_lock_domain_by_id(domid_t dom)
           d = rcu_dereference(d->next_in_hashbucket) )
     {
         if ( d->domain_id == dom )
-            return d;
+        {
+            rcu_lock_domain(d);
+            break;
+        }
     }
 
     rcu_read_unlock(&domlist_read_lock);
 
-    return NULL;
+    return d;
 }
 
 int rcu_lock_target_domain_by_id(domid_t dom, struct domain **d)