xref: /openbmc/linux/block/blk-mq-virtio.c (revision 3bf90eca)
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 void 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;
43 
44 fallback:
45 	blk_mq_map_queues(qmap);
46 }
47 EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);
48