block/blk-mq-virtio.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/device.h>
  14 #include <linux/blk-mq.h>
  15 #include <linux/blk-mq-virtio.h>
  16 #include <linux/virtio_config.h>
  17 #include <linux/module.h>
  18 #include "blk-mq.h"
  19
  20 /**
  21  * blk_mq_virtio_map_queues - provide a default queue mapping for virtio device
  22  * @set:        tagset to provide the mapping for
  23  * @vdev:       virtio device associated with @set.
  24  * @first_vec:  first interrupt vectors to use for queues (usually 0)
  25  *
  26  * This function assumes the virtio device @vdev has at least as many available
  27  * interrupt vetors as @set has queues.  It will then queuery the vector
  28  * corresponding to each queue for it's affinity mask and built queue mapping
  29  * that maps a queue to the CPUs that have irq affinity for the corresponding
  30  * vector.
  31  */
  32 int blk_mq_virtio_map_queues(struct blk_mq_queue_map *qmap,
  33                 struct virtio_device *vdev, int first_vec)
  34 {
  35         const struct cpumask *mask;
  36         unsigned int queue, cpu;
  37
  38         if (!vdev->config->get_vq_affinity)
  39                 goto fallback;
  40
  41         for (queue = 0; queue < qmap->nr_queues; queue++) {
  42                 mask = vdev->config->get_vq_affinity(vdev, first_vec + queue);
  43                 if (!mask)
  44                         goto fallback;
  45
  46                 for_each_cpu(cpu, mask)
  47                         qmap->mq_map[cpu] = qmap->queue_offset + queue;
  48         }
  49
  50         return 0;
  51 fallback:
  52         return blk_mq_map_queues(qmap);
  53 }
  54 EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);