[PATCH v2 3/4] x86/IRQ: direct-APIC-vector setting is now init-only

[Jan Beulich <jbeulich@xxxxxxxx>]

With all callers of alloc_direct_apic_vector() now being limited to BSP
setup, it and its helpers (whose other callers have already been init-
only) can become __init. As a result data items can be adjusted, too.

With alloc_direct_apic_vector() now being __init, it's meaningless to use
a lock, and the indirection is also pretty pointless. Drop both while at
it.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Re-work alloc_direct_apic_vector().

--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -161,7 +161,7 @@ static void intel_init_thermal(const str
     }
 
     if ( bsp )
-        alloc_direct_apic_vector(&thermal_apic_vector, 
intel_thermal_interrupt);
+        thermal_apic_vector = 
alloc_direct_apic_vector(intel_thermal_interrupt);
 
     /* The temperature transition interrupt handler setup */
     val = thermal_apic_vector;    /* our delivery vector */
@@ -689,7 +689,7 @@ static void intel_init_cmci(struct cpuin
     }
 
     if ( bsp )
-        alloc_direct_apic_vector(&cmci_apic_vector, cmci_interrupt);
+        cmci_apic_vector = alloc_direct_apic_vector(cmci_interrupt);
 
     apic = cmci_apic_vector;
     apic |= (APIC_DM_FIXED | APIC_LVT_MASKED);
--- a/xen/arch/x86/guest/xen/xen.c
+++ b/xen/arch/x86/guest/xen/xen.c
@@ -293,7 +293,7 @@ static void __init cf_check setup(void)
                XEN_LEGACY_MAX_VCPUS);
     }
 
-    alloc_direct_apic_vector(&evtchn_upcall_vector, xen_evtchn_upcall);
+    evtchn_upcall_vector = alloc_direct_apic_vector(xen_evtchn_upcall);
 
     BUG_ON(init_evtchn());
 }
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3181,10 +3181,10 @@ const struct hvm_function_table * __init
 
     if ( cpu_has_vmx_posted_intr_processing )
     {
-        alloc_direct_apic_vector(&posted_intr_vector, 
pi_notification_interrupt);
+        posted_intr_vector = 
alloc_direct_apic_vector(pi_notification_interrupt);
         if ( iommu_intpost )
         {
-            alloc_direct_apic_vector(&pi_wakeup_vector, pi_wakeup_interrupt);
+            pi_wakeup_vector = alloc_direct_apic_vector(pi_wakeup_interrupt);
 
             vmx_function_table.pi_update_irte = vmx_pi_update_irte;
         }
--- a/xen/arch/x86/include/asm/irq.h
+++ b/xen/arch/x86/include/asm/irq.h
@@ -119,7 +119,7 @@ uint8_t alloc_hipriority_vector(void);
 void free_lopriority_vector(uint8_t vector);
 
 void set_direct_apic_vector(uint8_t vector, void (*handler)(void));
-void alloc_direct_apic_vector(uint8_t *vector, void (*handler)(void));
+uint8_t alloc_direct_apic_vector(void (*handler)(void));
 
 void do_IRQ(struct cpu_user_regs *regs);
 
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -970,31 +970,28 @@ void pirq_set_affinity(struct domain *d,
 DEFINE_PER_CPU(unsigned int, irq_count);
 static DEFINE_PER_CPU(bool, check_eoi_deferral);
 
-uint8_t alloc_hipriority_vector(void)
+uint8_t __init alloc_hipriority_vector(void)
 {
-    static uint8_t next = FIRST_HIPRIORITY_VECTOR;
+    static uint8_t __initdata next = FIRST_HIPRIORITY_VECTOR;
     BUG_ON(next < FIRST_HIPRIORITY_VECTOR);
     BUG_ON(next > LAST_HIPRIORITY_VECTOR);
     return next++;
 }
 
-static void (*direct_apic_vector[X86_IDT_VECTORS])(void);
-void set_direct_apic_vector(uint8_t vector, void (*handler)(void))
+static void (*__ro_after_init direct_apic_vector[X86_IDT_VECTORS])(void);
+void __init set_direct_apic_vector(uint8_t vector, void (*handler)(void))
 {
     BUG_ON(direct_apic_vector[vector] != NULL);
     direct_apic_vector[vector] = handler;
 }
 
-void alloc_direct_apic_vector(uint8_t *vector, void (*handler)(void))
+uint8_t __init alloc_direct_apic_vector(void (*handler)(void))
 {
-    static DEFINE_SPINLOCK(lock);
+    uint8_t vec = alloc_hipriority_vector();
 
-    spin_lock(&lock);
-    if (*vector == 0) {
-        *vector = alloc_hipriority_vector();
-        set_direct_apic_vector(*vector, handler);
-    }
-    spin_unlock(&lock);
+    set_direct_apic_vector(vec, handler);
+
+    return vec;
 }
 
 /* This could free any vectors, but is needed only for low-prio ones. */