x86/dom0: propagate PVH vlapic EOIs to hardware

Current check for MSI EIO is missing a special case for PVH Dom0,
which doesn't have a hvm_irq_dpci struct but requires EIOs to be
forwarded to the physical lapic for passed-through devices.

Add a short-circuit to allow EOIs from PVH Dom0 to be propagated.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>

xen/drivers/passthrough/io.c

@@ -869,7 +869,8 @@ static int _hvm_dpci_msi_eoi(struct domain *d,
 
 void hvm_dpci_msi_eoi(struct domain *d, int vector)
 {
-    if ( !iommu_enabled || !hvm_domain_irq(d)->dpci )
+    if ( !iommu_enabled ||
+         (!hvm_domain_irq(d)->dpci && !is_hardware_domain(d)) )
        return;
 
     spin_lock(&d->event_lock);