1 files changed, 19 insertions, 2 deletions

diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index bde78d0098a4..c88baa4ff0e5 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -209,13 +209,30 @@ static int x2apic_cluster_probe(void)
                 return 0;
 }
 
+static const struct cpumask *x2apic_cluster_target_cpus(void)
+{
+        return cpu_all_mask;
+}
+
 /*
  * Each x2apic cluster is an allocation domain.
  */
 static void cluster_vector_allocation_domain(int cpu, struct cpumask *retmask,
                                              const struct cpumask *mask)
 {
-        cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
+        /*
+         * To minimize vector pressure, default case of boot, device bringup
+         * etc will use a single cpu for the interrupt destination.
+         *
+         * On explicit migration requests coming from irqbalance etc,
+         * interrupts will be routed to the x2apic cluster (cluster-id
+         * derived from the first cpu in the mask) members specified
+         * in the mask.
+         */
+        if (mask == x2apic_cluster_target_cpus())
+                cpumask_copy(retmask, cpumask_of(cpu));
+        else
+                cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
 }
 
 static struct apic apic_x2apic_cluster = {
@@ -229,7 +246,7 @@ static struct apic apic_x2apic_cluster = {
         .irq_delivery_mode              = dest_LowestPrio,
         .irq_dest_mode                  = 1, /* logical */
 
-        .target_cpus                    = online_target_cpus,
+        .target_cpus                    = x2apic_cluster_target_cpus,
         .disable_esr                    = 0,
         .dest_logical                   = APIC_DEST_LOGICAL,
         .check_apicid_used              = NULL,