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#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;
}
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