64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
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#include <linux/interrupt.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/cpu.h>
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static int get_first_sibling(unsigned int cpu)
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{
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unsigned int ret;
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ret = cpumask_first(topology_sibling_cpumask(cpu));
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if (ret < nr_cpu_ids)
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return ret;
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return cpu;
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}
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/*
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* Take a map of online CPUs and the number of available interrupt vectors
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* and generate an output cpumask suitable for spreading MSI/MSI-X vectors
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* so that they are distributed as good as possible around the CPUs. If
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* more vectors than CPUs are available we'll map one to each CPU,
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* otherwise we map one to the first sibling of each socket.
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*
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* If there are more vectors than CPUs we will still only have one bit
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* set per CPU, but interrupt code will keep on assigning the vectors from
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* the start of the bitmap until we run out of vectors.
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*/
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struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
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{
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struct cpumask *affinity_mask;
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unsigned int max_vecs = *nr_vecs;
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if (max_vecs == 1)
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return NULL;
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affinity_mask = kzalloc(cpumask_size(), GFP_KERNEL);
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if (!affinity_mask) {
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*nr_vecs = 1;
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return NULL;
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}
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get_online_cpus();
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if (max_vecs >= num_online_cpus()) {
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cpumask_copy(affinity_mask, cpu_online_mask);
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*nr_vecs = num_online_cpus();
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} else {
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unsigned int vecs = 0, cpu;
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for_each_online_cpu(cpu) {
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if (cpu == get_first_sibling(cpu)) {
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cpumask_set_cpu(cpu, affinity_mask);
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vecs++;
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}
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if (--max_vecs == 0)
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break;
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}
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*nr_vecs = vecs;
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}
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put_online_cpus();
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return affinity_mask;
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}
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