/*
   * Copyright (c) 2016 Christoph Hellwig.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   */
  #include <linux/device.h>
  #include <linux/blk-mq.h>
  #include <linux/blk-mq-virtio.h>
  #include <linux/virtio_config.h>
  #include <linux/module.h>
  #include "blk-mq.h"
  
  /**
   * blk_mq_virtio_map_queues - provide a default queue mapping for virtio device
   * @set:	tagset to provide the mapping for
   * @vdev:	virtio device associated with @set.
   * @first_vec:	first interrupt vectors to use for queues (usually 0)
   *
   * This function assumes the virtio device @vdev has at least as many available
   * interrupt vetors as @set has queues.  It will then queuery the vector
   * corresponding to each queue for it's affinity mask and built queue mapping
   * that maps a queue to the CPUs that have irq affinity for the corresponding
   * vector.
   */
  int blk_mq_virtio_map_queues(struct blk_mq_tag_set *set,
  		struct virtio_device *vdev, int first_vec)
  {
  	const struct cpumask *mask;
  	unsigned int queue, cpu;
  
  	if (!vdev->config->get_vq_affinity)
  		goto fallback;
  
  	for (queue = 0; queue < set->nr_hw_queues; queue++) {
  		mask = vdev->config->get_vq_affinity(vdev, first_vec + queue);
  		if (!mask)
  			goto fallback;
  
  		for_each_cpu(cpu, mask)
  			set->mq_map[cpu] = queue;
  	}
  
  	return 0;
  fallback:
  	return blk_mq_map_queues(set);
  }
  EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);