[Xen-devel] [PATCH 1/2] xen-netback: limit xen vif max queues number to online cpus

[Joe Jin <joe.jin@xxxxxxxxxx>]

Should not allocate xen vif queues number more than online cpus.

Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/net/xen-netback/netback.c |   28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index ec98d43..387fbd1 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -68,7 +68,9 @@ unsigned int rx_stall_timeout_msecs = 60000;
 module_param(rx_stall_timeout_msecs, uint, 0444);
 
 unsigned int xenvif_max_queues;
-module_param_named(max_queues, xenvif_max_queues, uint, 0644);
+static int xennet_set_max_queues(const char *val, struct kernel_param *kp);
+module_param_call(max_queues, xennet_set_max_queues, param_get_int,
+                 &xenvif_max_queues, 0600);
 MODULE_PARM_DESC(max_queues,
                 "Maximum number of queues per virtual interface");
 
@@ -107,6 +109,20 @@ static struct xen_netif_rx_response 
*make_rx_response(struct xenvif_queue *queue
                                             u16      size,
                                             u16      flags);
 
+static int xennet_set_max_queues(const char *val, struct kernel_param *kp)
+{
+       unsigned int cpus = num_online_cpus();
+       unsigned int max_queues = simple_strtoul(val, NULL, 10);
+
+       if (max_queues == 0 || max_queues > cpus) {
+               pr_info("max_queues %d is out of range [0 - %d]!\n", 
+                       max_queues, cpus);
+               return -EINVAL;
+       }
+
+       return param_set_int(val, kp);
+}
+
 static inline unsigned long idx_to_pfn(struct xenvif_queue *queue,
                                       u16 idx)
 {
@@ -2110,15 +2126,15 @@ int xenvif_dealloc_kthread(void *data)
 static int __init netback_init(void)
 {
        int rc = 0;
+       unsigned int cpus = num_online_cpus();
 
        if (!xen_domain())
                return -ENODEV;
 
-       /* Allow as many queues as there are CPUs if user has not
-        * specified a value.
-        */
-       if (xenvif_max_queues == 0)
-               xenvif_max_queues = num_online_cpus();
+       /* Allow at most as many queues as CPUs. */
+       if (xenvif_max_queues == 0 || xenvif_max_queues > cpus)
+               xenvif_max_queues = cpus;
+       pr_info("vif max_queues: %d\n", xenvif_max_queues);
 
        if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
                pr_info("fatal_skb_slots too small (%d), bump it to 
XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",
-- 
1.7.1



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