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Commit d62d8600 authored by Bob Liu's avatar Bob Liu Committed by Konrad Rzeszutek Wilk
Browse files

xen/blkback: get the number of hardware queues/rings from blkfront 



Backend advertises "multi-queue-max-queues" to front, also get the negotiated
number from "multi-queue-num-queues" written by blkfront.

Signed-off-by: default avatarBob Liu <bob.liu@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 2fb1ef4f

drivers/block/xen-blkback/blkback.c

+13 −0
Original line number Diff line number Diff line
@@ -83,6 +83,16 @@ module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); 
MODULE_PARM_DESC(max_persistent_grants,

                 "Maximum number of grants to map persistently");



/*

 * Maximum number of rings/queues blkback supports, allow as many queues as there

 * are CPUs if user has not specified a value.

 */

unsigned int xenblk_max_queues;

module_param_named(max_queues, xenblk_max_queues, uint, 0644);

MODULE_PARM_DESC(max_queues,

		 "Maximum number of hardware queues per virtual disk." \

		 "By default it is the number of online CPUs.");



/*

 * Maximum order of pages to be used for the shared ring between front and

 * backend, 4KB page granularity is used.
@@ -1483,6 +1493,9 @@ static int __init xen_blkif_init(void) 
		xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;

	}



	if (xenblk_max_queues == 0)

		xenblk_max_queues = num_online_cpus();



	rc = xen_blkif_interface_init();

	if (rc)

		goto failed_init;

drivers/block/xen-blkback/common.h

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
#include <xen/interface/io/protocols.h>



extern unsigned int xen_blkif_max_ring_order;

extern unsigned int xenblk_max_queues;

/*

 * This is the maximum number of segments that would be allowed in indirect

 * requests. This value will also be passed to the frontend.

drivers/block/xen-blkback/xenbus.c

+28 −6
Original line number Diff line number Diff line
@@ -181,12 +181,6 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) 
	blkif->st_print = jiffies;

	INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants);



	blkif->nr_rings = 1;

	if (xen_blkif_alloc_rings(blkif)) {

		kmem_cache_free(xen_blkif_cachep, blkif);

		return ERR_PTR(-ENOMEM);

	}



	return blkif;

}
@@ -595,6 +589,12 @@ static int xen_blkbk_probe(struct xenbus_device *dev, 
		goto fail;

	}



	/* Multi-queue: advertise how many queues are supported by us.*/

	err = xenbus_printf(XBT_NIL, dev->nodename,

			    "multi-queue-max-queues", "%u", xenblk_max_queues);

	if (err)

		pr_warn("Error writing multi-queue-max-queues\n");



	/* setup back pointer */

	be->blkif->be = be;
@@ -980,6 +980,7 @@ static int connect_ring(struct backend_info *be) 
	char *xspath;

	size_t xspathsize;

	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */

	unsigned int requested_num_queues = 0;



	pr_debug("%s %s\n", __func__, dev->otherend);
@@ -1007,6 +1008,27 @@ static int connect_ring(struct backend_info *be) 
	be->blkif->vbd.feature_gnt_persistent = pers_grants;

	be->blkif->vbd.overflow_max_grants = 0;



	/*

	 * Read the number of hardware queues from frontend.

	 */

	err = xenbus_scanf(XBT_NIL, dev->otherend, "multi-queue-num-queues",

			   "%u", &requested_num_queues);

	if (err < 0) {

		requested_num_queues = 1;

	} else {

		if (requested_num_queues > xenblk_max_queues

		    || requested_num_queues == 0) {

			/* Buggy or malicious guest. */

			xenbus_dev_fatal(dev, err,

					"guest requested %u queues, exceeding the maximum of %u.",

					requested_num_queues, xenblk_max_queues);

			return -ENOSYS;

		}

	}

	be->blkif->nr_rings = requested_num_queues;

	if (xen_blkif_alloc_rings(be->blkif))

		return -ENOMEM;



	pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,

		 be->blkif->nr_rings, be->blkif->blk_protocol, protocol,

		 pers_grants ? "persistent grants" : "");