[PATCH 1/4] x86/guest: move allocation of Xen upcall vector to init code

[Jan Beulich]

There's no need to do this every time init_evtchn() is called. Just do it
once when setting up CPU0. Drop the assertion as well, as
alloc_hipriority_vector() (called by alloc_direct_apic_vector()) uses more
restrictive BUG_ON() anyway. Then evtchn_upcall_vector can also validly
become ro-after-init, just that it needs to move out of init_evtchn().

Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/arch/x86/guest/xen/xen.c
+++ b/xen/arch/x86/guest/xen/xen.c
@@ -233,16 +233,12 @@ static void cf_check xen_evtchn_upcall(v
     ack_APIC_irq();
 }
 
+static uint8_t __ro_after_init evtchn_upcall_vector;
+
 static int init_evtchn(void)
 {
-    static uint8_t evtchn_upcall_vector;
     int rc;
 
-    if ( !evtchn_upcall_vector )
-        alloc_direct_apic_vector(&evtchn_upcall_vector, xen_evtchn_upcall);
-
-    ASSERT(evtchn_upcall_vector);
-
     rc = xen_hypercall_set_evtchn_upcall_vector(this_cpu(vcpu_id),
                                                 evtchn_upcall_vector);
     if ( rc )
@@ -293,6 +289,8 @@ static void __init cf_check setup(void)
                XEN_LEGACY_MAX_VCPUS);
     }
 
+    alloc_direct_apic_vector(&evtchn_upcall_vector, xen_evtchn_upcall);
+
     BUG_ON(init_evtchn());
 }