1 2 #include <linux/interrupt.h> 3 #include <linux/kernel.h> 4 #include <linux/slab.h> 5 #include <linux/cpu.h> 6 7 static int get_first_sibling(unsigned int cpu) 8 { 9 unsigned int ret; 10 11 ret = cpumask_first(topology_sibling_cpumask(cpu)); 12 if (ret < nr_cpu_ids) 13 return ret; 14 return cpu; 15 } 16 17 /* 18 * Take a map of online CPUs and the number of available interrupt vectors 19 * and generate an output cpumask suitable for spreading MSI/MSI-X vectors 20 * so that they are distributed as good as possible around the CPUs. If 21 * more vectors than CPUs are available we'll map one to each CPU, 22 * otherwise we map one to the first sibling of each socket. 23 * 24 * If there are more vectors than CPUs we will still only have one bit 25 * set per CPU, but interrupt code will keep on assigning the vectors from 26 * the start of the bitmap until we run out of vectors. 27 */ 28 struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs) 29 { 30 struct cpumask *affinity_mask; 31 unsigned int max_vecs = *nr_vecs; 32 33 if (max_vecs == 1) 34 return NULL; 35 36 affinity_mask = kzalloc(cpumask_size(), GFP_KERNEL); 37 if (!affinity_mask) { 38 *nr_vecs = 1; 39 return NULL; 40 } 41 42 if (max_vecs >= num_online_cpus()) { 43 cpumask_copy(affinity_mask, cpu_online_mask); 44 *nr_vecs = num_online_cpus(); 45 } else { 46 unsigned int vecs = 0, cpu; 47 48 for_each_online_cpu(cpu) { 49 if (cpu == get_first_sibling(cpu)) { 50 cpumask_set_cpu(cpu, affinity_mask); 51 vecs++; 52 } 53 54 if (--max_vecs == 0) 55 break; 56 } 57 *nr_vecs = vecs; 58 } 59 60 return affinity_mask; 61 } 62