x86/IRQ: constrain creator-domain-ID assertion

If init_one_irq_desc() fails, ->arch.creator_domid won't be set to the
expected value, and hence the assertion may trigger. Limit it to just
the success case of that function call.

Fixes: 92d9101eab ("x86: allow stubdom access to irq created for msi")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
master commit: d7127e06f6
master date: 2025-05-14 11:00:00 +0200

xen/arch/x86/irq.c

@@ -285,9 +285,9 @@ int create_irq(nodeid_t node, bool grant_access)
                 mask = NULL;
         }
         ret = assign_irq_vector(irq, mask);
-    }
 
-    ASSERT(desc->arch.creator_domid == DOMID_INVALID);
+        ASSERT(desc->arch.creator_domid == DOMID_INVALID);
+    }
 
     if (ret < 0)
     {