Re: [Xen-devel] [PATCH v5 08/10] xen/blkback: get the number of hardware queues/rings from blkfront

[Konrad Rzeszutek Wilk]

On Sat, Nov 14, 2015 at 11:12:17AM +0800, Bob Liu wrote:
> 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 
> ---
>  drivers/block/xen-blkback/blkback.c |   12 
>  drivers/block/xen-blkback/common.h  |1 +
>  drivers/block/xen-blkback/xenbus.c  |   34 --
>  3 files changed, 41 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/blkback.c 
> b/drivers/block/xen-blkback/blkback.c
> index fb5bfd4..acedc46 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -84,6 +84,15 @@ 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");

Added:
 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");
+"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 +1492,9 @@ 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 f2386e3..0833dc6 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 6c6e048..d83b790 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(>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: write how many queues are supported by the backend. */
> + err = xenbus_printf(XBT_NIL, dev->nodename,
> + "multi-queue-max-queues", "%u", xenblk_max_queues);
> + if (err)
> + pr_warn("Error writing multi-queue-num-queues\n");

s/num/max/

> +
>   /* 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", _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 -1;

And made this return -ENOSYS.


> + }
> + }
> + be->blkif->nr_rings = requested_num_queues;
> + if 

[Xen-devel] [PATCH v5 08/10] xen/blkback: get the number of hardware queues/rings from blkfront

[Bob Liu]

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 
---
 drivers/block/xen-blkback/blkback.c |   12 
 drivers/block/xen-blkback/common.h  |1 +
 drivers/block/xen-blkback/xenbus.c  |   34 --
 3 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index fb5bfd4..acedc46 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -84,6 +84,15 @@ 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");
+
+/*
  * Maximum order of pages to be used for the shared ring between front and
  * backend, 4KB page granularity is used.
  */
@@ -1483,6 +1492,9 @@ 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 f2386e3..0833dc6 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 6c6e048..d83b790 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(>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: write how many queues are supported by the backend. */
+   err = xenbus_printf(XBT_NIL, dev->nodename,
+   "multi-queue-max-queues", "%u", xenblk_max_queues);
+   if (err)
+   pr_warn("Error writing multi-queue-num-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", _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 -1;
+   }
+   }
+   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" : "");
-- 
1.7.10.4


___
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel