[PATCH v5 2/5] 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.

As the usage of this bitmap is tightly coupled with the VIRQ_DOM_EXC
event, it is meant to be used only by a single consumer in the system,
just like the VIRQ_DOM_EXC event.

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)
V3:
- use xvzalloc_array() (Jan Beulich)
- don't rename existing label (Jan Beulich)
V4:
- add __read_mostly (Jan Beulich)
- use __set_biz() (Jan Beulich)
- fix error handling in evtchn_bind_virq() (Jan Beulich)
V5:
- domain_init_states() may be called only if evtchn_bind_virq() has been
  called validly (Jan Beulich)
---
 xen/common/domain.c        | 60 ++++++++++++++++++++++++++++++++++++++
 xen/common/event_channel.c | 16 ++++++++++
 xen/include/xen/sched.h    |  3 ++
 3 files changed, 79 insertions(+)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index e33a0a5a21..87633b1f7b 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -34,6 +34,7 @@
 #include <xen/xenoprof.h>
 #include <xen/irq.h>
 #include <xen/argo.h>
+#include <xen/xvmalloc.h>
 #include <asm/p2m.h>
 #include <asm/processor.h>
 #include <public/sched.h>
@@ -138,6 +139,60 @@ bool __read_mostly vmtrace_available;
 
 bool __read_mostly vpmu_is_available;
 
+static DEFINE_SPINLOCK(dom_state_changed_lock);
+static unsigned long *__read_mostly 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 = xvzalloc_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);
+
+    XVFREE(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 +207,7 @@ 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 +895,7 @@ 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 +1161,7 @@ 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 +1351,8 @@ 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..aa947efba7 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -469,6 +469,7 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
     struct domain *d = current->domain;
     int            virq = bind->virq, vcpu = bind->vcpu;
     int            rc = 0;
+    bool           deinit_if_err = false;
 
     if ( (virq < 0) || (virq >= ARRAY_SIZE(v->virq_to_evtchn)) )
         return -EINVAL;
@@ -494,6 +495,15 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
         goto out;
     }
 
+    if ( virq == VIRQ_DOM_EXC )
+    {
+        rc = domain_init_states();
+        if ( rc )
+            goto out;
+
+        deinit_if_err = true;
+    }
+
     port = rc = evtchn_get_port(d, port);
     if ( rc < 0 )
     {
@@ -527,6 +537,9 @@ int evtchn_bind_virq(evtchn_bind_virq_t *bind, 
evtchn_port_t port)
  out:
     write_unlock(&d->event_lock);
 
+    if ( rc && deinit_if_err )
+        domain_deinit_states();
+
     return rc;
 }
 
@@ -730,6 +743,9 @@ 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