xen: allow global VIRQ handlers to be delegated to other domains

This patch sends global VIRQs to a domain designated as the VIRQ
handler
instead of sending all global VIRQ events to dom0. This is required in
order to run xenstored in a stubdom, because VIRQ_DOM_EXC must be sent
to xenstored for domain destruction to work properly.

This patch was inspired by the xenstored stubdomain patch series sent
to xen-devel by Alex Zeffertt in 2009.

Signed-off-by: Diego Ongaro <diego.ongaro@citrix.com>
Signed-off-by: Alex Zeffertt <alex.zeffertt@eu.citrix.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Keir Fraser <keir@xen.org>

5 files changed, 89 insertions, 8 deletions

diff --git a/xen/common/cpu.c b/xen/common/cpu.c
index 79abdb7b09..630881e5ab 100644
--- a/xen/common/cpu.c
+++ b/xen/common/cpu.c
@@ -108,7 +108,7 @@ int cpu_down(unsigned int cpu)
     notifier_rc = notifier_call_chain(&cpu_chain, CPU_DEAD, hcpu, NULL);
     BUG_ON(notifier_rc != NOTIFY_DONE);
 
-    send_guest_global_virq(dom0, VIRQ_PCPU_STATE);
+    send_global_virq(VIRQ_PCPU_STATE);
     cpu_hotplug_done();
     return 0;
 
@@ -148,7 +148,7 @@ int cpu_up(unsigned int cpu)
     notifier_rc = notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu, NULL);
     BUG_ON(notifier_rc != NOTIFY_DONE);
 
-    send_guest_global_virq(dom0, VIRQ_PCPU_STATE);
+    send_global_virq(VIRQ_PCPU_STATE);
 
     cpu_hotplug_done();
     return 0;
diff --git a/xen/common/domain.c b/xen/common/domain.c
index fd202100ef..500c7a210c 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -86,7 +86,7 @@ static void __domain_finalise_shutdown(struct domain *d)
     if ( (d->shutdown_code == SHUTDOWN_suspend) && d->suspend_evtchn )
         evtchn_send(d, d->suspend_evtchn);
     else
-        send_guest_global_virq(dom0, VIRQ_DOM_EXC);
+        send_global_virq(VIRQ_DOM_EXC);
 }
 
 static void vcpu_check_shutdown(struct vcpu *v)
@@ -480,7 +480,7 @@ int domain_kill(struct domain *d)
         }
         d->is_dying = DOMDYING_dead;
         put_domain(d);
-        send_guest_global_virq(dom0, VIRQ_DOM_EXC);
+        send_global_virq(VIRQ_DOM_EXC);
         /* fallthrough */
     case DOMDYING_dead:
         break;
@@ -621,7 +621,7 @@ void domain_pause_for_debugger(void)
     for_each_vcpu ( d, v )
         vcpu_sleep_nosync(v);
 
-    send_guest_global_virq(dom0, VIRQ_DEBUGGER);
+    send_global_virq(VIRQ_DEBUGGER);
 }
 
 /* Complete domain destroy after RCU readers are not holding old references. */
@@ -680,7 +680,7 @@ static void complete_domain_destroy(struct rcu_head *head)
     free_cpumask_var(d->domain_dirty_cpumask);
     free_domain_struct(d);
 
-    send_guest_global_virq(dom0, VIRQ_DOM_EXC);
+    send_global_virq(VIRQ_DOM_EXC);
 }
 
 /* Release resources belonging to task @p. */
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 5b0fc4a511..8001a916cc 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -995,6 +995,23 @@ long do_domctl(XEN_GUEST_HANDLE(xen_domctl_t) u_domctl)
     }
     break;
 
+    case XEN_DOMCTL_set_virq_handler:
+    {
+        struct domain *d;
+        uint32_t virq = op->u.set_virq_handler.virq;
+
+        ret = -ESRCH;
+        d = rcu_lock_domain_by_id(op->domain);
+        if ( d != NULL )
+        {
+            ret = xsm_set_virq_handler(d, virq);
+            if ( !ret )
+                ret = set_global_virq_handler(d, virq);
+            rcu_unlock_domain(d);
+        }
+    }
+    break;
+
     default:
         ret = arch_do_domctl(op, u_domctl);
         break;
diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index 921204237d..43bd16755e 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -689,7 +689,7 @@ void send_guest_vcpu_virq(struct vcpu *v, int virq)
     spin_unlock_irqrestore(&v->virq_lock, flags);
 }
 
-void send_guest_global_virq(struct domain *d, int virq)
+static void send_guest_global_virq(struct domain *d, int virq)
 {
     unsigned long flags;
     int port;
@@ -739,6 +739,68 @@ int send_guest_pirq(struct domain *d, const struct pirq *pirq)
     return evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
 }
 
+static struct domain *global_virq_handlers[NR_VIRQS] __read_mostly;
+
+static DEFINE_SPINLOCK(global_virq_handlers_lock);
+
+void send_global_virq(uint32_t virq)
+{
+    ASSERT(virq < NR_VIRQS);
+    ASSERT(virq_is_global(virq));
+
+    send_guest_global_virq(global_virq_handlers[virq] ?: dom0, virq);
+}
+
+int set_global_virq_handler(struct domain *d, uint32_t virq)
+{
+    struct domain *old;
+
+    if (virq >= NR_VIRQS)
+        return -EINVAL;
+    if (!virq_is_global(virq))
+        return -EINVAL;
+
+    if (global_virq_handlers[virq] == d)
+        return 0;
+
+    if (unlikely(!get_domain(d)))
+        return -EINVAL;
+
+    spin_lock(&global_virq_handlers_lock);
+    old = global_virq_handlers[virq];
+    global_virq_handlers[virq] = d;
+    spin_unlock(&global_virq_handlers_lock);
+
+    if (old != NULL)
+        put_domain(old);
+
+    return 0;
+}
+
+static void clear_global_virq_handlers(struct domain *d)
+{
+    uint32_t virq;
+    int put_count = 0;
+
+    spin_lock(&global_virq_handlers_lock);
+
+    for (virq = 0; virq < NR_VIRQS; virq++)
+    {
+        if (global_virq_handlers[virq] == d)
+        {
+            global_virq_handlers[virq] = NULL;
+            put_count++;
+        }
+    }
+
+    spin_unlock(&global_virq_handlers_lock);
+
+    while (put_count)
+    {
+        put_domain(d);
+        put_count--;
+    }
+}
 
 static long evtchn_status(evtchn_status_t *status)
 {
@@ -1160,6 +1222,8 @@ void evtchn_destroy(struct domain *d)
         d->evtchn[i] = NULL;
     }
     spin_unlock(&d->event_lock);
+
+    clear_global_virq_handlers(d);
 }
 
 
diff --git a/xen/common/trace.c b/xen/common/trace.c
index 5772f248f7..58cbf39be9 100644
--- a/xen/common/trace.c
+++ b/xen/common/trace.c
@@ -661,7 +661,7 @@ static inline void insert_lost_records(struct t_buf *buf)
  */
 static void trace_notify_dom0(unsigned long unused)
 {
-    send_guest_global_virq(dom0, VIRQ_TBUF);
+    send_global_virq(VIRQ_TBUF);
 }
 static DECLARE_SOFTIRQ_TASKLET(trace_notify_dom0_tasklet,
                                trace_notify_dom0, 0);