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 */
32int blk_mq_virtio_map_queues(struct blk_mq_tag_set *set,
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 < set->nr_hw_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			set->mq_map[cpu] = queue;
48	}
49
50	return 0;
51fallback:
52	return blk_mq_map_queues(set);
53}
54EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);