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-rw-r--r--kernel/irq/Makefile1
-rw-r--r--kernel/irq/affinity.c61
2 files changed, 62 insertions, 0 deletions
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index 2ee42e95a3ce..1d3ee3169202 100644
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_GENERIC_IRQ_MIGRATION) += cpuhotplug.o
obj-$(CONFIG_PM_SLEEP) += pm.o
obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o
obj-$(CONFIG_GENERIC_IRQ_IPI) += ipi.o
+obj-$(CONFIG_SMP) += affinity.o
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
new file mode 100644
index 000000000000..f68959341c0f
--- /dev/null
+++ b/kernel/irq/affinity.c
@@ -0,0 +1,61 @@
+
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/cpu.h>
+
+static int get_first_sibling(unsigned int cpu)
+{
+ unsigned int ret;
+
+ ret = cpumask_first(topology_sibling_cpumask(cpu));
+ if (ret < nr_cpu_ids)
+ return ret;
+ return cpu;
+}
+
+/*
+ * Take a map of online CPUs and the number of available interrupt vectors
+ * and generate an output cpumask suitable for spreading MSI/MSI-X vectors
+ * so that they are distributed as good as possible around the CPUs. If
+ * more vectors than CPUs are available we'll map one to each CPU,
+ * otherwise we map one to the first sibling of each socket.
+ *
+ * If there are more vectors than CPUs we will still only have one bit
+ * set per CPU, but interrupt code will keep on assigning the vectors from
+ * the start of the bitmap until we run out of vectors.
+ */
+struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
+{
+ struct cpumask *affinity_mask;
+ unsigned int max_vecs = *nr_vecs;
+
+ if (max_vecs == 1)
+ return NULL;
+
+ affinity_mask = kzalloc(cpumask_size(), GFP_KERNEL);
+ if (!affinity_mask) {
+ *nr_vecs = 1;
+ return NULL;
+ }
+
+ if (max_vecs >= num_online_cpus()) {
+ cpumask_copy(affinity_mask, cpu_online_mask);
+ *nr_vecs = num_online_cpus();
+ } else {
+ unsigned int vecs = 0, cpu;
+
+ for_each_online_cpu(cpu) {
+ if (cpu == get_first_sibling(cpu)) {
+ cpumask_set_cpu(cpu, affinity_mask);
+ vecs++;
+ }
+
+ if (--max_vecs == 0)
+ break;
+ }
+ *nr_vecs = vecs;
+ }
+
+ return affinity_mask;
+}