xen: remove workaround to inject evtchn_irq on irq enable

evtchn_upcall_pending is already set by common code at vcpu creation,
therefore on ARM we also need to call vgic_vcpu_inject_irq for it.
Currently we do that from vgic_enable_irqs as a workaround.

Do this properly by introducing an appropriate arch specific hook:
arch_evtchn_inject. arch_evtchn_inject is called by map_vcpu_info to
inject the evtchn irq into the guest. On ARM is implemented by calling
vgic_vcpu_inject_irq.

On x86 guests typically don't call VCPUOP_register_vcpu_info on vcpu0,
therefore avoiding the issue. However theoretically they could call
VCPUOP_register_vcpu_info on vcpu0 and in that case Xen would need to
inject the event channel notification into the guest if the guest is
HVM. So implement arch_evtchn_inject on x86 by calling
hvm_assert_evtchn_irq.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien.grall@linaro.org>

xen/arch/arm/vgic.c

@@ -264,20 +264,10 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
         v_target = d->arch.vgic.handler->get_target_vcpu(v, irq);
         p = irq_to_pending(v_target, irq);
         set_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
-        /* We need to force the first injection of evtchn_irq because
-         * evtchn_upcall_pending is already set by common code on vcpu
-         * creation. */
-        if ( irq == v_target->domain->arch.evtchn_irq &&
-             vcpu_info(current, evtchn_upcall_pending) &&
-             list_empty(&p->inflight) )
-            vgic_vcpu_inject_irq(v_target, irq);
-        else {
-            unsigned long flags;
-            spin_lock_irqsave(&v_target->arch.vgic.lock, flags);
-            if ( !list_empty(&p->inflight) && !test_bit(GIC_IRQ_GUEST_VISIBLE, &p->status) )
-                gic_raise_guest_irq(v_target, irq, p->priority);
-            spin_unlock_irqrestore(&v_target->arch.vgic.lock, flags);
-        }
+        spin_lock_irqsave(&v_target->arch.vgic.lock, flags);
+        if ( !list_empty(&p->inflight) && !test_bit(GIC_IRQ_GUEST_VISIBLE, &p->status) )
+            gic_raise_guest_irq(v_target, irq, p->priority);
+        spin_unlock_irqrestore(&v_target->arch.vgic.lock, flags);
         if ( p->desc != NULL )
         {
             irq_set_affinity(p->desc, cpumask_of(v_target->processor));
@@ -433,6 +423,11 @@ void vgic_vcpu_inject_spi(struct domain *d, unsigned int irq)
     vgic_vcpu_inject_irq(v, irq);
 }
 
+void arch_evtchn_inject(struct vcpu *v)
+{
+    vgic_vcpu_inject_irq(v, v->domain->arch.evtchn_irq);
+}
+
 /*
  * Local variables:
  * mode: C

xen/arch/x86/hvm/irq.c

@@ -468,6 +468,12 @@ int hvm_local_events_need_delivery(struct vcpu *v)
     return !hvm_interrupt_blocked(v, intack);
 }
 
+void arch_evtchn_inject(struct vcpu *v)
+{
+    if ( has_hvm_container_vcpu(v) )
+        hvm_assert_evtchn_irq(v);
+}
+
 static void irq_dump(struct domain *d)
 {
     struct hvm_irq *hvm_irq = &d->arch.hvm_domain.irq;

xen/common/domain.c

@@ -1102,6 +1102,7 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned offset)
     vcpu_info(v, evtchn_upcall_pending) = 1;
     for ( i = 0; i < BITS_PER_EVTCHN_WORD(d); i++ )
         set_bit(i, &vcpu_info(v, evtchn_pending_sel));
+    arch_evtchn_inject(v);
 
     return 0;
 }

xen/include/xen/event.h

@@ -69,6 +69,9 @@ int guest_enabled_event(struct vcpu *v, uint32_t virq);
 /* Notify remote end of a Xen-attached event channel.*/
 void notify_via_xen_event_channel(struct domain *ld, int lport);
 
+/* Inject an event channel notification into the guest */
+void arch_evtchn_inject(struct vcpu *v);
+
 /*
  * Internal event channel object storage.
  *