IRQ: allocate CPU masks dynamically

This includes delaying the initialization of dynamically created IRQs
until their actual first use and some further elimination of uses of
struct irq_cfg.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/ia64/linux-xen/irq_ia64.c
+++ b/xen/arch/ia64/linux-xen/irq_ia64.c
@@ -303,6 +303,9 @@ int __init request_irq_vector(unsigned i
 void __init
 init_IRQ (void)
 {
+#ifdef XEN
+	BUG_ON(init_irq_data());
+#endif
 	register_percpu_irq(IA64_SPURIOUS_INT_VECTOR, NULL);
 #ifdef CONFIG_SMP
 	register_percpu_irq(IA64_IPI_VECTOR, &ipi_irqaction);
--- a/xen/arch/ia64/xen/irq.c
+++ b/xen/arch/ia64/xen/irq.c
@@ -74,17 +74,30 @@ unsigned int __ia64_local_vector_to_irq 
 /*
  * Controller mappings for all interrupt sources:
  */
-irq_desc_t irq_desc[NR_IRQS] = {
-	[0 ... NR_IRQS-1] = {
-		.status = IRQ_DISABLED,
-		.handler = &no_irq_type,
-		.lock = SPIN_LOCK_UNLOCKED
-		.arch = {
-		        .vector = -1,
-		        .cpu_mask = CPU_MASK_ALL,
-		}
+irq_desc_t irq_desc[NR_IRQS];
+
+int __init arch_init_one_irq_desc(struct irq_desc *desc)
+{
+	if (!alloc_cpumask_var(&desc->arch.cpu_mask))
+		return -ENOMEM;
+
+	desc->arch.vector = -1;
+	cpumask_setall(desc->arch.cpu_mask);
+
+	return 0;
+}
+
+int __init init_irq_data(void)
+{
+	unsigned int irq;
+
+	for (irq = 0; irq < NR_IRQS; irq++) {
+		struct irq_desc *desc = irq_to_desc(irq);
+
+		desc->irq = irq;
+		init_one_irq_desc(desc);
 	}
-};
+}
 
 void __do_IRQ_guest(int irq);
 
--- a/xen/arch/x86/i8259.c
+++ b/xen/arch/x86/i8259.c
@@ -398,7 +398,7 @@ void __init init_IRQ(void)
         
         desc->handler = &i8259A_irq_type;
         per_cpu(vector_irq, cpu)[FIRST_LEGACY_VECTOR + irq] = irq;
-        cpumask_copy(&desc->arch.cpu_mask, cpumask_of(cpu));
+        cpumask_copy(desc->arch.cpu_mask, cpumask_of(cpu));
         desc->arch.vector = FIRST_LEGACY_VECTOR + irq;
     }
     
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -648,20 +648,21 @@ static int pin_2_irq(int idx, int apic, 
 void /*__init*/ setup_ioapic_dest(void)
 {
     int pin, ioapic, irq, irq_entry;
-    struct irq_cfg *cfg;
 
     if (skip_ioapic_setup)
         return;
 
     for (ioapic = 0; ioapic < nr_ioapics; ioapic++) {
         for (pin = 0; pin < nr_ioapic_entries[ioapic]; pin++) {
+            struct irq_desc *desc;
+
             irq_entry = find_irq_entry(ioapic, pin, mp_INT);
             if (irq_entry == -1)
                 continue;
             irq = pin_2_irq(irq_entry, ioapic, pin);
-            cfg = irq_cfg(irq);
-            BUG_ON(cpus_empty(cfg->cpu_mask));
-            set_ioapic_affinity_irq(irq_to_desc(irq), &cfg->cpu_mask);
+            desc = irq_to_desc(irq);
+            BUG_ON(cpumask_empty(desc->arch.cpu_mask));
+            set_ioapic_affinity_irq(desc, desc->arch.cpu_mask);
         }
 
     }
@@ -956,12 +957,12 @@ static void __init setup_IO_APIC_irqs(vo
     struct IO_APIC_route_entry entry;
     int apic, pin, idx, irq, first_notcon = 1, vector;
     unsigned long flags;
-    struct irq_cfg *cfg;
 
     apic_printk(APIC_VERBOSE, KERN_DEBUG "init IO_APIC IRQs\n");
 
     for (apic = 0; apic < nr_ioapics; apic++) {
         for (pin = 0; pin < nr_ioapic_entries[apic]; pin++) {
+            struct irq_desc *desc;
 
             /*
              * add it to the IO-APIC irq-routing table:
@@ -1016,9 +1017,9 @@ static void __init setup_IO_APIC_irqs(vo
                 if (!apic && platform_legacy_irq(irq))
                     disable_8259A_irq(irq_to_desc(irq));
             }
-            cfg = irq_cfg(irq);
+            desc = irq_to_desc(irq);
             SET_DEST(entry.dest.dest32, entry.dest.logical.logical_dest,
-                     cpu_mask_to_apicid(&cfg->cpu_mask));
+                     cpu_mask_to_apicid(desc->arch.cpu_mask));
             spin_lock_irqsave(&ioapic_lock, flags);
             __ioapic_write_entry(apic, pin, 0, entry);
             set_native_irq_info(irq, TARGET_CPUS);
@@ -2372,7 +2373,7 @@ int ioapic_guest_write(unsigned long phy
     rte.vector = cfg->vector;
 
     SET_DEST(rte.dest.dest32, rte.dest.logical.logical_dest,
-             cpu_mask_to_apicid(&cfg->cpu_mask));
+             cpu_mask_to_apicid(desc->arch.cpu_mask));
 
     io_apic_write(apic, 0x10 + 2 * pin, *(((int *)&rte) + 0));
     io_apic_write(apic, 0x11 + 2 * pin, *(((int *)&rte) + 1));
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -25,6 +25,7 @@
 #include <public/physdev.h>
 
 static void parse_irq_vector_map_param(char *s);
+static int __assign_irq_vector(int irq, struct irq_desc *, const cpumask_t *);
 
 /* opt_noirqbalance: If true, software IRQ balancing/affinity is disabled. */
 bool_t __read_mostly opt_noirqbalance = 0;
@@ -110,7 +111,7 @@ static int __init __bind_irq_vector(int 
 {
     cpumask_t online_mask;
     int cpu;
-    struct irq_cfg *cfg = irq_cfg(irq);
+    struct irq_desc *desc = irq_to_desc(irq);
 
     BUG_ON((unsigned)irq >= nr_irqs);
     BUG_ON((unsigned)vector >= NR_VECTORS);
@@ -118,21 +119,22 @@ static int __init __bind_irq_vector(int 
     cpumask_and(&online_mask, cpu_mask, &cpu_online_map);
     if (cpumask_empty(&online_mask))
         return -EINVAL;
-    if ((cfg->vector == vector) && cpumask_equal(&cfg->cpu_mask, &online_mask))
+    if ( (desc->arch.vector == vector) &&
+         cpumask_equal(desc->arch.cpu_mask, &online_mask) )
         return 0;
-    if (cfg->vector != IRQ_VECTOR_UNASSIGNED) 
+    if ( desc->arch.vector != IRQ_VECTOR_UNASSIGNED )
         return -EBUSY;
     trace_irq_mask(TRC_HW_IRQ_BIND_VECTOR, irq, vector, &online_mask);
     for_each_cpu_mask(cpu, online_mask)
         per_cpu(vector_irq, cpu)[vector] = irq;
-    cfg->vector = vector;
-    cpumask_copy(&cfg->cpu_mask, &online_mask);
-    if ( cfg->used_vectors )
+    desc->arch.vector = vector;
+    cpumask_copy(desc->arch.cpu_mask, &online_mask);
+    if ( desc->arch.used_vectors )
     {
-        ASSERT(!test_bit(vector, cfg->used_vectors));
-        set_bit(vector, cfg->used_vectors);
+        ASSERT(!test_bit(vector, desc->arch.used_vectors));
+        set_bit(vector, desc->arch.used_vectors);
     }
-    cfg->used = IRQ_USED;
+    desc->arch.used = IRQ_USED;
     if (IO_APIC_IRQ(irq))
         irq_vector[irq] = vector;
     return 0;
@@ -166,14 +168,17 @@ int create_irq(void)
 {
     unsigned long flags;
     int irq, ret;
-    irq = -ENOSPC;
+    struct irq_desc *desc;
 
     spin_lock_irqsave(&vector_lock, flags);
 
     irq = find_unassigned_irq();
     if (irq < 0)
          goto out;
-    ret = __assign_irq_vector(irq, irq_cfg(irq), TARGET_CPUS);
+    desc = irq_to_desc(irq);
+    ret = init_one_irq_desc(desc);
+    if (!ret)
+        ret = __assign_irq_vector(irq, desc, TARGET_CPUS);
     if (ret < 0)
         irq = ret;
 out:
@@ -197,7 +202,7 @@ static void dynamic_irq_cleanup(unsigned
     desc->msi_desc = NULL;
     desc->handler = &no_irq_type;
     desc->arch.used_vectors = NULL;
-    cpumask_setall(&desc->affinity);
+    cpumask_setall(desc->affinity);
     spin_unlock_irqrestore(&desc->lock, flags);
 
     /* Wait to make sure it's not being used on another CPU */
@@ -211,38 +216,38 @@ static void __clear_irq_vector(int irq)
 {
     int cpu, vector, old_vector;
     cpumask_t tmp_mask;
-    struct irq_cfg *cfg = irq_cfg(irq);
+    struct irq_desc *desc = irq_to_desc(irq);
 
-    BUG_ON(!cfg->vector);
+    BUG_ON(!desc->arch.vector);
 
-    /* Always clear cfg->vector */
-    vector = cfg->vector;
-    cpumask_and(&tmp_mask, &cfg->cpu_mask, &cpu_online_map);
+    /* Always clear desc->arch.vector */
+    vector = desc->arch.vector;
+    cpumask_and(&tmp_mask, desc->arch.cpu_mask, &cpu_online_map);
 
     for_each_cpu_mask(cpu, tmp_mask) {
         ASSERT( per_cpu(vector_irq, cpu)[vector] == irq );
         per_cpu(vector_irq, cpu)[vector] = -1;
     }
 
-    cfg->vector = IRQ_VECTOR_UNASSIGNED;
-    cpumask_clear(&cfg->cpu_mask);
+    desc->arch.vector = IRQ_VECTOR_UNASSIGNED;
+    cpumask_clear(desc->arch.cpu_mask);
 
-    if ( cfg->used_vectors )
+    if ( desc->arch.used_vectors )
     {
-        ASSERT(test_bit(vector, cfg->used_vectors));
-        clear_bit(vector, cfg->used_vectors);
+        ASSERT(test_bit(vector, desc->arch.used_vectors));
+        clear_bit(vector, desc->arch.used_vectors);
     }
 
-    cfg->used = IRQ_UNUSED;
+    desc->arch.used = IRQ_UNUSED;
 
     trace_irq_mask(TRC_HW_IRQ_CLEAR_VECTOR, irq, vector, &tmp_mask);
 
-    if (likely(!cfg->move_in_progress))
+    if ( likely(!desc->arch.move_in_progress) )
         return;
 
-    /* If we were in motion, also clear cfg->old_vector */
-    old_vector = cfg->old_vector;
-    cpumask_and(&tmp_mask, &cfg->old_cpu_mask, &cpu_online_map);
+    /* If we were in motion, also clear desc->arch.old_vector */
+    old_vector = desc->arch.old_vector;
+    cpumask_and(&tmp_mask, desc->arch.old_cpu_mask, &cpu_online_map);
 
     for_each_cpu_mask(cpu, tmp_mask) {
         ASSERT( per_cpu(vector_irq, cpu)[old_vector] == irq );
@@ -250,16 +255,16 @@ static void __clear_irq_vector(int irq)
         per_cpu(vector_irq, cpu)[old_vector] = -1;
      }
 
-    cfg->old_vector = IRQ_VECTOR_UNASSIGNED;
-    cpumask_clear(&cfg->old_cpu_mask);
+    desc->arch.old_vector = IRQ_VECTOR_UNASSIGNED;
+    cpumask_clear(desc->arch.old_cpu_mask);
 
-    if ( cfg->used_vectors )
+    if ( desc->arch.used_vectors )
     {
-        ASSERT(test_bit(old_vector, cfg->used_vectors));
-        clear_bit(old_vector, cfg->used_vectors);
+        ASSERT(test_bit(old_vector, desc->arch.used_vectors));
+        clear_bit(old_vector, desc->arch.used_vectors);
     }
 
-    cfg->move_in_progress = 0;
+    desc->arch.move_in_progress = 0;
 }
 
 void clear_irq_vector(int irq)
@@ -296,25 +301,28 @@ int irq_to_vector(int irq)
     return vector;
 }
 
-static void __init init_one_irq_desc(struct irq_desc *desc)
+int arch_init_one_irq_desc(struct irq_desc *desc)
 {
-    desc->status  = IRQ_DISABLED;
-    desc->handler = &no_irq_type;
-    desc->action  = NULL;
-    desc->msi_desc = NULL;
-    spin_lock_init(&desc->lock);
-    cpumask_setall(&desc->affinity);
-    INIT_LIST_HEAD(&desc->rl_link);
-}
+    if ( !zalloc_cpumask_var(&desc->arch.cpu_mask) )
+        return -ENOMEM;
+
+    if ( !alloc_cpumask_var(&desc->arch.old_cpu_mask) )
+    {
+        free_cpumask_var(desc->arch.cpu_mask);
+        return -ENOMEM;
+    }
 
-static void __init init_one_irq_cfg(struct irq_cfg *cfg)
-{
-    cfg->vector = IRQ_VECTOR_UNASSIGNED;
-    cfg->old_vector = IRQ_VECTOR_UNASSIGNED;
-    cpumask_clear(&cfg->cpu_mask);
-    cpumask_clear(&cfg->old_cpu_mask);
-    cfg->used_vectors = NULL;
-    cfg->used = IRQ_UNUSED;
+    if ( !alloc_cpumask_var(&desc->arch.pending_mask) )
+    {
+        free_cpumask_var(desc->arch.old_cpu_mask);
+        free_cpumask_var(desc->arch.cpu_mask);
+        return -ENOMEM;
+    }
+
+    desc->arch.vector = IRQ_VECTOR_UNASSIGNED;
+    desc->arch.old_vector = IRQ_VECTOR_UNASSIGNED;
+
+    return 0;
 }
 
 int __init init_irq_data(void)
@@ -331,12 +339,13 @@ int __init init_irq_data(void)
     if ( !irq_desc || !irq_vector )
         return -ENOMEM;
 
-    for (irq = 0; irq < nr_irqs; irq++) {
+    for (irq = 0; irq < nr_irqs_gsi; irq++) {
         desc = irq_to_desc(irq);
         desc->irq = irq;
         init_one_irq_desc(desc);
-        init_one_irq_cfg(&desc->arch);
     }
+    for (; irq < nr_irqs; irq++)
+        irq_to_desc(irq)->irq = irq;
 
     /* Never allocate the hypercall vector or Linux/BSD fast-trap vector. */
     set_bit(LEGACY_SYSCALL_VECTOR, used_vectors);
@@ -403,7 +412,8 @@ static vmask_t *irq_get_used_vector_mask
     return ret;
 }
 
-int __assign_irq_vector(int irq, struct irq_cfg *cfg, const cpumask_t *mask)
+static int __assign_irq_vector(
+    int irq, struct irq_desc *desc, const cpumask_t *mask)
 {
     /*
      * NOTE! The local APIC isn't very good at handling
@@ -426,13 +436,13 @@ int __assign_irq_vector(int irq, struct 
     old_vector = irq_to_vector(irq);
     if (old_vector) {
         cpumask_and(&tmp_mask, mask, &cpu_online_map);
-        if (cpumask_intersects(&tmp_mask, &cfg->cpu_mask)) {
-            cfg->vector = old_vector;
+        if (cpumask_intersects(&tmp_mask, desc->arch.cpu_mask)) {
+            desc->arch.vector = old_vector;
             return 0;
         }
     }
 
-    if ((cfg->move_in_progress) || cfg->move_cleanup_count)
+    if ( desc->arch.move_in_progress || desc->arch.move_cleanup_count )
         return -EAGAIN;
 
     err = -ENOSPC;
@@ -440,9 +450,9 @@ int __assign_irq_vector(int irq, struct 
     /* This is the only place normal IRQs are ever marked
      * as "in use".  If they're not in use yet, check to see
      * if we need to assign a global vector mask. */
-    if ( cfg->used == IRQ_USED )
+    if ( desc->arch.used == IRQ_USED )
     {
-        irq_used_vectors = cfg->used_vectors;
+        irq_used_vectors = desc->arch.used_vectors;
     }
     else
         irq_used_vectors = irq_get_used_vector_mask(irq);
@@ -485,29 +495,29 @@ next:
         current_offset = offset;
         local_irq_save(flags);
         if (old_vector) {
-            cfg->move_in_progress = 1;
-            cpumask_copy(&cfg->old_cpu_mask, &cfg->cpu_mask);
-            cfg->old_vector = cfg->vector;
+            desc->arch.move_in_progress = 1;
+            cpumask_copy(desc->arch.old_cpu_mask, desc->arch.cpu_mask);
+            desc->arch.old_vector = desc->arch.vector;
         }
         trace_irq_mask(TRC_HW_IRQ_ASSIGN_VECTOR, irq, vector, &tmp_mask);
         for_each_cpu_mask(new_cpu, tmp_mask)
             per_cpu(vector_irq, new_cpu)[vector] = irq;
-        cfg->vector = vector;
-        cpumask_copy(&cfg->cpu_mask, &tmp_mask);
+        desc->arch.vector = vector;
+        cpumask_copy(desc->arch.cpu_mask, &tmp_mask);
 
-        cfg->used = IRQ_USED;
-        ASSERT((cfg->used_vectors == NULL)
-               || (cfg->used_vectors == irq_used_vectors));
-        cfg->used_vectors = irq_used_vectors;
+        desc->arch.used = IRQ_USED;
+        ASSERT((desc->arch.used_vectors == NULL)
+               || (desc->arch.used_vectors == irq_used_vectors));
+        desc->arch.used_vectors = irq_used_vectors;
 
         if (IO_APIC_IRQ(irq))
             irq_vector[irq] = vector;
 
-        if ( cfg->used_vectors )
+        if ( desc->arch.used_vectors )
         {
-            ASSERT(!test_bit(vector, cfg->used_vectors));
+            ASSERT(!test_bit(vector, desc->arch.used_vectors));
 
-            set_bit(vector, cfg->used_vectors);
+            set_bit(vector, desc->arch.used_vectors);
         }
 
         err = 0;
@@ -521,16 +531,15 @@ int assign_irq_vector(int irq)
 {
     int ret;
     unsigned long flags;
-    struct irq_cfg *cfg = irq_cfg(irq);
     struct irq_desc *desc = irq_to_desc(irq);
     
     BUG_ON(irq >= nr_irqs || irq <0);
 
     spin_lock_irqsave(&vector_lock, flags);
-    ret = __assign_irq_vector(irq, cfg, TARGET_CPUS);
+    ret = __assign_irq_vector(irq, desc, TARGET_CPUS);
     if (!ret) {
-        ret = cfg->vector;
-        cpumask_copy(&desc->affinity, &cfg->cpu_mask);
+        ret = desc->arch.vector;
+        cpumask_copy(desc->affinity, desc->arch.cpu_mask);
     }
     spin_unlock_irqrestore(&vector_lock, flags);
     return ret;
@@ -543,15 +552,16 @@ int assign_irq_vector(int irq)
 void __setup_vector_irq(int cpu)
 {
     int irq, vector;
-    struct irq_cfg *cfg;
 
     /* Clear vector_irq */
     for (vector = 0; vector < NR_VECTORS; ++vector)
         per_cpu(vector_irq, cpu)[vector] = -1;
     /* Mark the inuse vectors */
     for (irq = 0; irq < nr_irqs; ++irq) {
-        cfg = irq_cfg(irq);
-        if (!cpu_isset(cpu, cfg->cpu_mask))
+        struct irq_desc *desc = irq_to_desc(irq);
+
+        if (!irq_desc_initialized(desc) ||
+            !cpumask_test_cpu(cpu, desc->arch.cpu_mask))
             continue;
         vector = irq_to_vector(irq);
         per_cpu(vector_irq, cpu)[vector] = irq;
@@ -560,12 +570,14 @@ void __setup_vector_irq(int cpu)
 
 void move_masked_irq(struct irq_desc *desc)
 {
+    cpumask_t *pending_mask = desc->arch.pending_mask;
+
     if (likely(!(desc->status & IRQ_MOVE_PENDING)))
         return;
     
     desc->status &= ~IRQ_MOVE_PENDING;
 
-    if (unlikely(cpus_empty(desc->pending_mask)))
+    if (unlikely(cpumask_empty(pending_mask)))
         return;
 
     if (!desc->handler->set_affinity)
@@ -580,10 +592,10 @@ void move_masked_irq(struct irq_desc *de
      *
      * For correct operation this depends on the caller masking the irqs.
      */
-    if (likely(cpus_intersects(desc->pending_mask, cpu_online_map)))
-        desc->handler->set_affinity(desc, &desc->pending_mask);
+    if ( likely(cpumask_intersects(pending_mask, &cpu_online_map)) )
+        desc->handler->set_affinity(desc, pending_mask);
 
-    cpumask_clear(&desc->pending_mask);
+    cpumask_clear(pending_mask);
 }
 
 void move_native_irq(struct irq_desc *desc)
@@ -626,7 +638,8 @@ fastcall void smp_irq_move_cleanup_inter
         if (!desc->arch.move_cleanup_count)
             goto unlock;
 
-        if (vector == desc->arch.vector && cpumask_test_cpu(me, &desc->arch.cpu_mask))
+        if ( vector == desc->arch.vector &&
+             cpumask_test_cpu(me, desc->arch.cpu_mask) )
             goto unlock;
 
         irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
@@ -653,7 +666,7 @@ fastcall void smp_irq_move_cleanup_inter
         if ( desc->arch.move_cleanup_count == 0 )
         {
             desc->arch.old_vector = IRQ_VECTOR_UNASSIGNED;
-            cpumask_clear(&desc->arch.old_cpu_mask);
+            cpumask_clear(desc->arch.old_cpu_mask);
 
             if ( desc->arch.used_vectors )
             {
@@ -673,7 +686,7 @@ static void send_cleanup_vector(struct i
 {
     cpumask_t cleanup_mask;
 
-    cpumask_and(&cleanup_mask, &desc->arch.old_cpu_mask, &cpu_online_map);
+    cpumask_and(&cleanup_mask, desc->arch.old_cpu_mask, &cpu_online_map);
     desc->arch.move_cleanup_count = cpumask_weight(&cleanup_mask);
     genapic->send_IPI_mask(&cleanup_mask, IRQ_MOVE_CLEANUP_VECTOR);
 
@@ -690,7 +703,8 @@ void irq_complete_move(struct irq_desc *
     vector = get_irq_regs()->entry_vector;
     me = smp_processor_id();
 
-    if (vector == desc->arch.vector && cpumask_test_cpu(me, &desc->arch.cpu_mask))
+    if ( vector == desc->arch.vector &&
+         cpumask_test_cpu(me, desc->arch.cpu_mask) )
         send_cleanup_vector(desc);
 }
 
@@ -708,15 +722,15 @@ unsigned int set_desc_affinity(struct ir
 
     local_irq_save(flags);
     lock_vector_lock();
-    ret = __assign_irq_vector(irq, &desc->arch, mask);
+    ret = __assign_irq_vector(irq, desc, mask);
     unlock_vector_lock();
     local_irq_restore(flags);
 
     if (ret < 0)
         return BAD_APICID;
 
-    cpumask_copy(&desc->affinity, mask);
-    cpumask_and(&dest_mask, mask, &desc->arch.cpu_mask);
+    cpumask_copy(desc->affinity, mask);
+    cpumask_and(&dest_mask, mask, desc->arch.cpu_mask);
 
     return cpu_mask_to_apicid(&dest_mask);
 }
@@ -730,7 +744,7 @@ void irq_set_affinity(struct irq_desc *d
     ASSERT(spin_is_locked(&desc->lock));
     desc->status &= ~IRQ_MOVE_PENDING;
     wmb();
-    cpumask_copy(&desc->pending_mask, mask);
+    cpumask_copy(desc->arch.pending_mask, mask);
     wmb();
     desc->status |= IRQ_MOVE_PENDING;
 }
@@ -1992,13 +2006,13 @@ static void dump_irqs(unsigned char key)
 
         desc = irq_to_desc(irq);
 
-        if ( !desc->handler || desc->handler == &no_irq_type )
+        if ( !irq_desc_initialized(desc) || desc->handler == &no_irq_type )
             continue;
 
         spin_lock_irqsave(&desc->lock, flags);
 
         cpumask_scnprintf(keyhandler_scratch, sizeof(keyhandler_scratch),
-                          &desc->affinity);
+                          desc->affinity);
         printk("   IRQ:%4d affinity:%s vec:%02x type=%-15s"
                " status=%08x ",
                irq, keyhandler_scratch, desc->arch.vector,
@@ -2073,10 +2087,12 @@ void fixup_irqs(void)
             continue;
 
         desc = irq_to_desc(irq);
+        if ( !irq_desc_initialized(desc) )
+            continue;
 
         spin_lock(&desc->lock);
 
-        cpumask_copy(&affinity, &desc->affinity);
+        cpumask_copy(&affinity, desc->affinity);
         if ( !desc->action || cpumask_subset(&affinity, &cpu_online_map) )
         {
             spin_unlock(&desc->lock);
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -125,13 +125,13 @@ void msi_compose_msg(struct irq_desc *de
     unsigned dest;
     int vector = desc->arch.vector;
 
-    if ( cpumask_empty(&desc->arch.cpu_mask) ) {
+    if ( cpumask_empty(desc->arch.cpu_mask) ) {
         dprintk(XENLOG_ERR,"%s, compose msi message error!!\n", __func__);
         return;
     }
 
     if ( vector ) {
-        dest = cpu_mask_to_apicid(&desc->arch.cpu_mask);
+        dest = cpu_mask_to_apicid(desc->arch.cpu_mask);
 
         msg->address_hi = MSI_ADDR_BASE_HI;
         msg->address_lo =
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -1011,7 +1011,7 @@ void __init smp_intr_init(void)
         irq_vector[irq] = FIRST_HIPRIORITY_VECTOR + seridx + 1;
         per_cpu(vector_irq, cpu)[FIRST_HIPRIORITY_VECTOR + seridx + 1] = irq;
         irq_to_desc(irq)->arch.vector = FIRST_HIPRIORITY_VECTOR + seridx + 1;
-        cpumask_copy(&irq_to_desc(irq)->arch.cpu_mask, &cpu_online_map);
+        cpumask_copy(irq_to_desc(irq)->arch.cpu_mask, &cpu_online_map);
     }
 
     /* IPI for cleanuping vectors after irq move */
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -5,6 +5,7 @@ obj-y += domctl.o
 obj-y += domain.o
 obj-y += event_channel.o
 obj-y += grant_table.o
+obj-y += irq.o
 obj-y += kernel.o
 obj-y += keyhandler.o
 obj-y += kexec.o
--- /dev/null
+++ a/xen/common/irq.c
@@ -0,0 +1,28 @@
+#include <xen/config.h>
+#include <xen/irq.h>
+
+int init_one_irq_desc(struct irq_desc *desc)
+{
+    int err;
+
+    if (irq_desc_initialized(desc))
+        return 0;
+
+    if ( !alloc_cpumask_var(&desc->affinity) )
+        return -ENOMEM;
+
+    desc->status = IRQ_DISABLED;
+    desc->handler = &no_irq_type;
+    spin_lock_init(&desc->lock);
+    cpumask_setall(desc->affinity);
+    INIT_LIST_HEAD(&desc->rl_link);
+
+    err = arch_init_one_irq_desc(desc);
+    if ( err )
+    {
+        free_cpumask_var(desc->affinity);
+        desc->handler = NULL;
+    }
+
+    return err;
+}
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1965,17 +1965,18 @@ static int init_vtd_hw(void)
     struct iommu_flush *flush = NULL;
     int ret;
     unsigned long flags;
-    struct irq_cfg *cfg;
 
     /*
      * Basic VT-d HW init: set VT-d interrupt, clear VT-d faults.  
      */
     for_each_drhd_unit ( drhd )
     {
+        struct irq_desc *desc;
+
         iommu = drhd->iommu;
 
-        cfg = irq_cfg(iommu->irq);
-        dma_msi_set_affinity(irq_to_desc(iommu->irq), &cfg->cpu_mask);
+        desc = irq_to_desc(iommu->irq);
+        dma_msi_set_affinity(desc, desc->arch.cpu_mask);
 
         clear_fault_bits(iommu);
 
--- a/xen/include/asm-ia64/linux-xen/asm/irq.h
+++ b/xen/include/asm-ia64/linux-xen/asm/irq.h
@@ -18,8 +18,10 @@
 struct irq_cfg {
 #define arch_irq_desc irq_cfg
         int  vector;
-        cpumask_t cpu_mask;
+        cpumask_var_t cpu_mask;
 };
+
+int init_irq_data(void);
 #endif
 
 static __inline__ int
--- a/xen/include/asm-x86/irq.h
+++ b/xen/include/asm-x86/irq.h
@@ -33,8 +33,9 @@ struct irq_cfg {
 #define arch_irq_desc irq_cfg
         s16 vector;                  /* vector itself is only 8 bits, */
         s16 old_vector;              /* but we use -1 for unassigned  */
-        cpumask_t cpu_mask;
-        cpumask_t old_cpu_mask;
+        cpumask_var_t cpu_mask;
+        cpumask_var_t old_cpu_mask;
+        cpumask_var_t pending_mask;
         unsigned move_cleanup_count;
         vmask_t *used_vectors;
         u8 move_in_progress : 1;
@@ -174,8 +175,6 @@ void __setup_vector_irq(int cpu);
 void move_native_irq(struct irq_desc *);
 void move_masked_irq(struct irq_desc *);
 
-int __assign_irq_vector(int irq, struct irq_cfg *, const cpumask_t *);
-
 int bind_irq_vector(int irq, int vector, const cpumask_t *);
 
 void irq_set_affinity(struct irq_desc *, const cpumask_t *mask);
--- a/xen/include/xen/irq.h
+++ b/xen/include/xen/irq.h
@@ -76,8 +76,7 @@ typedef struct irq_desc {
     int irq;
     spinlock_t lock;
     struct arch_irq_desc arch;
-    cpumask_t affinity;
-    cpumask_t pending_mask;  /* IRQ migration pending mask */
+    cpumask_var_t affinity;
 
     /* irq ratelimit */
     s_time_t rl_quantum_start;
@@ -85,6 +84,11 @@ typedef struct irq_desc {
     struct list_head rl_link;
 } __cacheline_aligned irq_desc_t;
 
+int init_one_irq_desc(struct irq_desc *);
+int arch_init_one_irq_desc(struct irq_desc *);
+
+#define irq_desc_initialized(desc) ((desc)->handler != NULL)
+
 #if defined(__ia64__)
 extern irq_desc_t irq_desc[NR_VECTORS];
 
@@ -153,7 +157,7 @@ extern irq_desc_t *pirq_spin_lock_irq_de
 
 static inline void set_native_irq_info(unsigned int irq, const cpumask_t *mask)
 {
-    cpumask_copy(&irq_desc[irq].affinity, mask);
+    cpumask_copy(irq_to_desc(irq)->affinity, mask);
 }
 
 unsigned int set_desc_affinity(struct irq_desc *, const cpumask_t *);