[PATCH v2 4/7] 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>
---
V2:
- use DOMID_FIRST_RESERVED instead of DOMID_MASK + 1 (Jan Beulich)
- use const (Jan Beulich)
- move call of domain_reset_states() into evtchn_bind_virq() (Jan Beulich)
- dynamically allocate dom_state_changed bitmap (Jan Beulich)
---
 xen/common/domain.c        | 59 ++++++++++++++++++++++++++++++++++++++
 xen/common/event_channel.c | 20 +++++++++++--
 xen/include/xen/sched.h    |  3 ++
 3 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index e33a0a5a21..4e3a593a9d 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -138,6 +138,60 @@ bool __read_mostly vmtrace_available;
 
 bool __read_mostly vpmu_is_available;
 
+static DEFINE_SPINLOCK(dom_state_changed_lock);
+static unsigned long *dom_state_changed;
+
+int domain_init_states(void)
+{
+    const struct domain *d;
+    int rc = -ENOMEM;
+
+    spin_lock(&dom_state_changed_lock);
+
+    if ( dom_state_changed )
+        bitmap_zero(dom_state_changed, DOMID_FIRST_RESERVED);
+    else
+    {
+        dom_state_changed = xzalloc_array(unsigned long,
+                                          BITS_TO_LONGS(DOMID_FIRST_RESERVED));
+        if ( !dom_state_changed )
+            goto unlock;
+    }
+
+    rcu_read_lock(&domlist_read_lock);
+
+    for_each_domain ( d )
+        set_bit(d->domain_id, dom_state_changed);
+
+    rcu_read_unlock(&domlist_read_lock);
+
+    rc = 0;
+
+ unlock:
+    spin_unlock(&dom_state_changed_lock);
+
+    return rc;
+}
+
+void domain_deinit_states(void)
+{
+    spin_lock(&dom_state_changed_lock);
+
+    XFREE(dom_state_changed);
+
+    spin_unlock(&dom_state_changed_lock);
+}
+
+static void domain_changed_state(const struct domain *d)
+{
+    spin_lock(&dom_state_changed_lock);
+
+    if ( dom_state_changed )
+        set_bit(d->domain_id, dom_state_changed);
+
+    spin_unlock(&dom_state_changed_lock);
+}
+
 static void __domain_finalise_shutdown(struct domain *d)
 {
     struct vcpu *v;
@@ -152,6 +206,7 @@ static void __domain_finalise_shutdown(struct domain *d)
             return;
 
     d->is_shut_down = 1;
+    domain_changed_state(d);
     if ( (d->shutdown_code == SHUTDOWN_suspend) && d->suspend_evtchn )
         evtchn_send(d, d->suspend_evtchn);
     else
@@ -839,6 +894,7 @@ struct domain *domain_create(domid_t domid,
      */
     domlist_insert(d);
 
+    domain_changed_state(d);
     memcpy(d->handle, config->handle, sizeof(d->handle));
 
     return d;
@@ -1104,6 +1160,7 @@ 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);
+        domain_changed_state(d);
         put_domain(d);
         send_global_virq(VIRQ_DOM_EXC);
         /* fallthrough */
@@ -1293,6 +1350,8 @@ static void cf_check complete_domain_destroy(struct 
rcu_head *head)
 
     xfree(d->vcpu);
 
+    domain_changed_state(d);
+
     _domain_destroy(d);
 
     send_global_virq(VIRQ_DOM_EXC);
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 8db2ca4ba2..cd7bad68c0 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -485,20 +485,27 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
     if ( (v = domain_vcpu(d, vcpu)) == NULL )
         return -ENOENT;
 
+    if ( virq == VIRQ_DOM_EXC )
+    {
+        rc = domain_init_states();
+        if ( rc )
+            goto out;
+    }
+
     write_lock(&d->event_lock);
 
     if ( read_atomic(&v->virq_to_evtchn[virq]) )
     {
         rc = -EEXIST;
         gdprintk(XENLOG_WARNING, "EVTCHNOP failure: error %d\n", rc);
-        goto out;
+        goto unlock;
     }
 
     port = rc = evtchn_get_port(d, port);
     if ( rc < 0 )
     {
         gdprintk(XENLOG_WARNING, "EVTCHNOP failure: error %d\n", rc);
-        goto out;
+        goto unlock;
     }
 
     rc = 0;
@@ -524,9 +531,13 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
      */
     write_atomic(&v->virq_to_evtchn[virq], port);
 
- out:
+ unlock:
     write_unlock(&d->event_lock);
 
+ out:
+    if ( rc )
+        domain_deinit_states();
+
     return rc;
 }
 
@@ -730,6 +741,9 @@ int evtchn_close(struct domain *d1, int port1, bool guest)
         struct vcpu *v;
         unsigned long flags;
 
+        if ( chn1->u.virq == VIRQ_DOM_EXC )
+            domain_deinit_states();
+
         v = d1->vcpu[virq_is_global(chn1->u.virq) ? 0 : chn1->notify_vcpu_id];
 
         write_lock_irqsave(&v->virq_lock, flags);
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 711668e028..16684bbaf9 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -800,6 +800,9 @@ void domain_resume(struct domain *d);
 
 int domain_soft_reset(struct domain *d, bool resuming);
 
+int domain_init_states(void);
+void domain_deinit_states(void);
+
 int vcpu_start_shutdown_deferral(struct vcpu *v);
 void vcpu_end_shutdown_deferral(struct vcpu *v);
 
-- 
2.43.0