x86, ioapic: Improve handling of i8259A irq init

Since we already track the number of legacy vectors by nr_legacy_irqs, we
can avoid use static vector allocations -- we can use dynamic one.
Signed-off-by: Alek Du <alek.du@intel.com>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80D01@orsmsx508.amr.corp.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/apic/io_apic.c

@@ -140,27 +140,10 @@ static struct irq_pin_list *get_one_free_irq_2_pin(int node)
 
 /* irq_cfg is indexed by the sum of all RTEs in all I/O APICs. */
 #ifdef CONFIG_SPARSE_IRQ
-static struct irq_cfg irq_cfgx[] = {
+static struct irq_cfg irq_cfgx[NR_IRQS_LEGACY];
 #else
-static struct irq_cfg irq_cfgx[NR_IRQS] = {
+static struct irq_cfg irq_cfgx[NR_IRQS];
 #endif
-	[0]  = { .vector = IRQ0_VECTOR,  },
-	[1]  = { .vector = IRQ1_VECTOR,  },
-	[2]  = { .vector = IRQ2_VECTOR,  },
-	[3]  = { .vector = IRQ3_VECTOR,  },
-	[4]  = { .vector = IRQ4_VECTOR,  },
-	[5]  = { .vector = IRQ5_VECTOR,  },
-	[6]  = { .vector = IRQ6_VECTOR,  },
-	[7]  = { .vector = IRQ7_VECTOR,  },
-	[8]  = { .vector = IRQ8_VECTOR,  },
-	[9]  = { .vector = IRQ9_VECTOR,  },
-	[10] = { .vector = IRQ10_VECTOR, },
-	[11] = { .vector = IRQ11_VECTOR, },
-	[12] = { .vector = IRQ12_VECTOR, },
-	[13] = { .vector = IRQ13_VECTOR, },
-	[14] = { .vector = IRQ14_VECTOR, },
-	[15] = { .vector = IRQ15_VECTOR, },
-};
 
 void __init io_apic_disable_legacy(void)
 {
@@ -181,6 +164,8 @@ int __init arch_early_irq_init(void)
 	node= cpu_to_node(boot_cpu_id);
 
 	for (i = 0; i < count; i++) {
+		if (i < nr_legacy_irqs)
+			cfg[i].vector = IRQ0_VECTOR + i;
 		desc = irq_to_desc(i);
 		desc->chip_data = &cfg[i];
 		zalloc_cpumask_var_node(&cfg[i].domain, GFP_NOWAIT, node);