xen: fix hvm_domain_use_pirq's behavior

hvm_domain_use_pirq should return true when the guest is using a
certain pirq, no matter if the corresponding event channel is
currently enabled or disabled.  As an additional complication, qemu is
going to request pirqs for passthrough devices even for Xen unaware
HVM guests, so we need to wait for an event channel to be connected
before considering the pirq of a passthrough device as "in use".

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

xen/arch/x86/irq.c

@@ -2027,6 +2027,5 @@ int unmap_domain_pirq_emuirq(struct domain *d, int pirq)
 bool_t hvm_domain_use_pirq(const struct domain *d, const struct pirq *pirq)
 {
     return is_hvm_domain(d) && pirq &&
-           pirq->arch.hvm.emuirq != IRQ_UNBOUND &&
-           pirq->evtchn != 0;
+           pirq->arch.hvm.emuirq != IRQ_UNBOUND; 
 }

xen/arch/x86/physdev.c

@@ -196,9 +196,6 @@ int physdev_map_pirq(domid_t domid, int type, int *index, int *pirq_p,
     if ( ret == 0 )
         *pirq_p = pirq;
 
-    if ( !ret && is_hvm_domain(d) )
-        map_domain_emuirq_pirq(d, pirq, IRQ_PT);
-
  done:
     spin_unlock(&d->event_lock);
     spin_unlock(&pcidevs_lock);
@@ -271,7 +268,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
              v->domain->arch.pv_domain.pirq_eoi_map )
             evtchn_unmask(pirq->evtchn);
         if ( !is_hvm_domain(v->domain) ||
-             pirq->arch.hvm.emuirq == IRQ_PT )
+             domain_pirq_to_irq(v->domain, eoi.irq) > 0 )
             pirq_guest_eoi(pirq);
         spin_unlock(&v->domain->event_lock);
         ret = 0;
@@ -331,7 +328,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE(void) arg)
             break;
         irq_status_query.flags = 0;
         if ( is_hvm_domain(v->domain) &&
-             domain_pirq_to_emuirq(v->domain, irq) != IRQ_PT )
+             domain_pirq_to_irq(v->domain, irq) <= 0 )
         {
             ret = copy_to_guest(arg, &irq_status_query, 1) ? -EFAULT : 0;
             break;

xen/common/event_channel.c

@@ -366,6 +366,9 @@ static long evtchn_bind_pirq(evtchn_bind_pirq_t *bind)
 
     bind->port = port;
 
+    if ( is_hvm_domain(d) && domain_pirq_to_irq(d, pirq) > 0 )
+        map_domain_emuirq_pirq(d, pirq, IRQ_PT);
+
  out:
     spin_unlock(&d->event_lock);
 
@@ -419,6 +422,8 @@ static long __evtchn_close(struct domain *d1, int port1)
         pirq->evtchn = 0;
         pirq_cleanup_check(pirq, d1);
         unlink_pirq_port(chn1, d1->vcpu[chn1->notify_vcpu_id]);
+        if ( is_hvm_domain(d1) && domain_pirq_to_irq(d1, pirq->pirq) > 0 )
+            unmap_domain_pirq_emuirq(d1, pirq->pirq);
         break;
     }