#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;	} 	get_online_cpus();	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;	}	put_online_cpus(); 	return affinity_mask;}