block/blk-mq-pci.c

   1 /*
   2  * Copyright (c) 2016 Christoph Hellwig.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms and conditions of the GNU General Public License,
   6  * version 2, as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  11  * more details.
  12  */
  13 #include <linux/kobject.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/blk-mq.h>
  16 #include <linux/blk-mq-pci.h>
  17 #include <linux/pci.h>
  18 #include <linux/module.h>
  19
  20 /**
  21  * blk_mq_pci_map_queues - provide a default queue mapping for PCI device
  22  * @set:        tagset to provide the mapping for
  23  * @pdev:       PCI device associated with @set.
  24  *
  25  * This function assumes the PCI device @pdev has at least as many available
  26  * interrupt vectors as @set has queues.  It will then query the vector
  27  * corresponding to each queue for it's affinity mask and built queue mapping
  28  * that maps a queue to the CPUs that have irq affinity for the corresponding
  29  * vector.
  30  */
  31 int blk_mq_pci_map_queues(struct blk_mq_tag_set *set, struct pci_dev *pdev)
  32 {
  33         const struct cpumask *mask;
  34         unsigned int queue, cpu;
  35
  36         for (queue = 0; queue < set->nr_hw_queues; queue++) {
  37                 mask = pci_irq_get_affinity(pdev, queue);
  38                 if (!mask)
  39                         goto fallback;
  40
  41                 for_each_cpu(cpu, mask)
  42                         set->mq_map[cpu] = queue;
  43         }
  44
  45         return 0;
  46
  47 fallback:
  48         WARN_ON_ONCE(set->nr_hw_queues > 1);
  49         for_each_possible_cpu(cpu)
  50                 set->mq_map[cpu] = 0;
  51         return 0;
  52 }
  53 EXPORT_SYMBOL_GPL(blk_mq_pci_map_queues);