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-rw-r--r--drivers/block/xen-blkback/blkback.c13
-rw-r--r--drivers/block/xen-blkback/common.h1
-rw-r--r--drivers/block/xen-blkback/xenbus.c34
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
@@ -84,6 +84,16 @@ 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 <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.
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" : "");