Drivers: hv: vmbus: Further improve CPU affiliation logic

Keep track of CPU affiliations of sub-channels within the scope of the primary
channel. This will allow us to better distribute the load amongst available
CPUs.
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel_mgmt.c

@@ -448,8 +448,24 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
 	cpumask_xor(&available_mask, alloced_mask,
 		    cpumask_of_node(primary->numa_node));
 
-	cur_cpu = cpumask_next(-1, &available_mask);
-	cpumask_set_cpu(cur_cpu, alloced_mask);
+	cur_cpu = -1;
+	while (true) {
+		cur_cpu = cpumask_next(cur_cpu, &available_mask);
+		if (cur_cpu >= nr_cpu_ids) {
+			cur_cpu = -1;
+			cpumask_copy(&available_mask,
+				     cpumask_of_node(primary->numa_node));
+			continue;
+		}
+
+		if (!cpumask_test_cpu(cur_cpu,
+				&primary->alloced_cpus_in_node)) {
+			cpumask_set_cpu(cur_cpu,
+					&primary->alloced_cpus_in_node);
+			cpumask_set_cpu(cur_cpu, alloced_mask);
+			break;
+		}
+	}
 
 	channel->target_cpu = cur_cpu;
 	channel->target_vp = hv_context.vp_index[cur_cpu];

include/linux/hyperv.h

@@ -699,6 +699,7 @@ struct vmbus_channel {
 	/*
 	 * State to manage the CPU affiliation of channels.
 	 */
+	struct cpumask alloced_cpus_in_node;
 	int numa_node;
 	/*
 	 * Support for sub-channels. For high performance devices,