From d62d86000316d7ef38e1c2e9602c3ce6d1cb57bd Mon Sep 17 00:00:00 2001 From: Bob Liu Date: Sat, 14 Nov 2015 11:12:17 +0800 Subject: [PATCH] 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: Bob Liu Signed-off-by: Konrad Rzeszutek Wilk --- drivers/block/xen-blkback/blkback.c | 13 +++++++++++ drivers/block/xen-blkback/common.h | 1 + drivers/block/xen-blkback/xenbus.c | 34 ++++++++++++++++++++++++----- 3 files changed, 42 insertions(+), 6 deletions(-) diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index 4fd8640d146c..18b27770d80b 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -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; diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 310eff3cf43f..847444dc1df4 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -46,6 +46,7 @@ #include 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. diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index f5bfedd0e948..0d6bb9383a68 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -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" : ""); -- 2.20.1