[PATCH RFC 2/4] xen: add bitmap to indicate per-domain state changes

[Juergen Gross <jgross@xxxxxxxx>]

Add a bitmap with one bit per possible domid indicating the respective
domain has changed its state (created, deleted, dying, crashed,
shutdown).

Registering the VIRQ_DOM_EXC event will result in setting the bits for
all existing domains and resetting all other bits.

Resetting a bit will be done in a future patch.

This information is needed for Xenstore to keep track of all domains.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/domain.c        | 22 ++++++++++++++++++++++
 xen/common/event_channel.c |  2 ++
 xen/include/xen/sched.h    |  2 ++
 3 files changed, 26 insertions(+)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 755349b93f..14a427e2ef 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -87,6 +87,22 @@ bool __read_mostly vmtrace_available;
 /* Unique domain identifier, protected by domctl lock. */
 static uint64_t unique_id;
 
+static DECLARE_BITMAP(dom_state_changed, DOMID_MASK + 1);
+
+void domain_reset_states(void)
+{
+    struct domain *d;
+
+    bitmap_zero(dom_state_changed, DOMID_MASK + 1);
+
+    rcu_read_lock(&domlist_read_lock);
+
+    for_each_domain ( d )
+        set_bit(d->domain_id, dom_state_changed);
+
+    rcu_read_unlock(&domlist_read_lock);
+}
+
 static void __domain_finalise_shutdown(struct domain *d)
 {
     struct vcpu *v;
@@ -101,6 +117,7 @@ static void __domain_finalise_shutdown(struct domain *d)
             return;
 
     d->is_shut_down = 1;
+    set_bit(d->domain_id, dom_state_changed);
     if ( (d->shutdown_code == SHUTDOWN_suspend) && d->suspend_evtchn )
         evtchn_send(d, d->suspend_evtchn);
     else
@@ -720,6 +737,8 @@ struct domain *domain_create(domid_t domid,
         rcu_assign_pointer(domain_hash[DOMAIN_HASH(domid)], d);
         spin_unlock(&domlist_update_lock);
 
+        set_bit(d->domain_id, dom_state_changed);
+
         memcpy(d->handle, config->handle, sizeof(d->handle));
     }
 
@@ -954,6 +973,7 @@ int domain_kill(struct domain *d)
         /* Mem event cleanup has to go here because the rings 
          * have to be put before we call put_domain. */
         vm_event_cleanup(d);
+        set_bit(d->domain_id, dom_state_changed);
         put_domain(d);
         send_global_virq(VIRQ_DOM_EXC);
         /* fallthrough */
@@ -1141,6 +1161,8 @@ static void complete_domain_destroy(struct rcu_head *head)
 
     xfree(d->vcpu);
 
+    set_bit(d->domain_id, dom_state_changed);
+
     _domain_destroy(d);
 
     send_global_virq(VIRQ_DOM_EXC);
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index da88ad141a..e2a416052b 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1218,6 +1218,8 @@ long do_event_channel_op(int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         rc = evtchn_bind_virq(&bind_virq, 0);
         if ( !rc && __copy_to_guest(arg, &bind_virq, 1) )
             rc = -EFAULT; /* Cleaning up here would be a mess! */
+        if ( !rc && bind_virq.virq == VIRQ_DOM_EXC )
+            domain_reset_states();
         break;
     }
 
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index b827c5af8d..2ae26bc50e 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -730,6 +730,8 @@ void domain_resume(struct domain *d);
 
 int domain_soft_reset(struct domain *d, bool resuming);
 
+void domain_reset_states(void);
+
 int vcpu_start_shutdown_deferral(struct vcpu *v);
 void vcpu_end_shutdown_deferral(struct vcpu *v);
 
-- 
2.26.2