block/blk-mq-virtio.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2016 Christoph Hellwig.
   4  */
   5 #include <linux/device.h>
   6 #include <linux/blk-mq.h>
   7 #include <linux/blk-mq-virtio.h>
   8 #include <linux/virtio_config.h>
   9 #include <linux/module.h>
  10 #include "blk-mq.h"
  11
  12 /**
  13  * blk_mq_virtio_map_queues - provide a default queue mapping for virtio device
  14  * @qmap:       CPU to hardware queue map.
  15  * @vdev:       virtio device to provide a mapping for.
  16  * @first_vec:  first interrupt vectors to use for queues (usually 0)
  17  *
  18  * This function assumes the virtio device @vdev has at least as many available
  19  * interrupt vectors as @set has queues.  It will then query the vector
  20  * corresponding to each queue for it's affinity mask and built queue mapping
  21  * that maps a queue to the CPUs that have irq affinity for the corresponding
  22  * vector.
  23  */
  24 int blk_mq_virtio_map_queues(struct blk_mq_queue_map *qmap,
  25                 struct virtio_device *vdev, int first_vec)
  26 {
  27         const struct cpumask *mask;
  28         unsigned int queue, cpu;
  29
  30         if (!vdev->config->get_vq_affinity)
  31                 goto fallback;
  32
  33         for (queue = 0; queue < qmap->nr_queues; queue++) {
  34                 mask = vdev->config->get_vq_affinity(vdev, first_vec + queue);
  35                 if (!mask)
  36                         goto fallback;
  37
  38                 for_each_cpu(cpu, mask)
  39                         qmap->mq_map[cpu] = qmap->queue_offset + queue;
  40         }
  41
  42         return 0;
  43 fallback:
  44         return blk_mq_map_queues(qmap);
  45 }
  46 EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);