Drivers: hv: vmbus: Implement per-CPU mapping of relid to channel

Currently the mapping of the relID to channel is done under the protection of a
single spin lock. Starting with ws2012, each channel is bound to a specific VCPU
in the guest. Use this binding to eliminate the spin lock by setting up
per-cpu state for mapping relId to the channel.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 6f7fdd9a7e77..6c8b032cacba 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -149,6 +149,7 @@ static struct vmbus_channel *alloc_channel(void)
 	spin_lock_init(&channel->sc_lock);
 
 	INIT_LIST_HEAD(&channel->sc_list);
+	INIT_LIST_HEAD(&channel->percpu_list);
 
 	channel->controlwq = create_workqueue("hv_vmbus_ctl");
 	if (!channel->controlwq) {
@@ -188,7 +189,20 @@ static void free_channel(struct vmbus_channel *channel)
 	queue_work(vmbus_connection.work_queue, &channel->work);
 }
 
+static void percpu_channel_enq(void *arg)
+{
+	struct vmbus_channel *channel = arg;
+	int cpu = smp_processor_id();
+
+	list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
+}
 
+static void percpu_channel_deq(void *arg)
+{
+	struct vmbus_channel *channel = arg;
+
+	list_del(&channel->percpu_list);
+}
 
 /*
  * vmbus_process_rescind_offer -
@@ -210,6 +224,12 @@ static void vmbus_process_rescind_offer(struct work_struct *work)
 	msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
 	vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
 
+	if (channel->target_cpu != smp_processor_id())
+		smp_call_function_single(channel->target_cpu,
+					 percpu_channel_deq, channel, true);
+	else
+		percpu_channel_deq(channel);
+
 	if (channel->primary_channel == NULL) {
 		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
 		list_del(&channel->listentry);
@@ -245,6 +265,7 @@ static void vmbus_process_offer(struct work_struct *work)
 							work);
 	struct vmbus_channel *channel;
 	bool fnew = true;
+	bool enq = false;
 	int ret;
 	unsigned long flags;
 
@@ -264,12 +285,22 @@ static void vmbus_process_offer(struct work_struct *work)
 		}
 	}
 
-	if (fnew)
+	if (fnew) {
 		list_add_tail(&newchannel->listentry,
 			      &vmbus_connection.chn_list);
+		enq = true;
+	}
 
 	spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
 
+	if (enq) {
+		if (newchannel->target_cpu != smp_processor_id())
+			smp_call_function_single(newchannel->target_cpu,
+						 percpu_channel_enq,
+						 newchannel, true);
+		else
+			percpu_channel_enq(newchannel);
+	}
 	if (!fnew) {
 		/*
 		 * Check to see if this is a sub-channel.
@@ -282,6 +313,14 @@ static void vmbus_process_offer(struct work_struct *work)
 			spin_lock_irqsave(&channel->sc_lock, flags);
 			list_add_tail(&newchannel->sc_list, &channel->sc_list);
 			spin_unlock_irqrestore(&channel->sc_lock, flags);
+
+			if (newchannel->target_cpu != smp_processor_id())
+				smp_call_function_single(newchannel->target_cpu,
+							 percpu_channel_enq,
+							 newchannel, true);
+			else
+				percpu_channel_enq(newchannel);
+
 			newchannel->state = CHANNEL_OPEN_STATE;
 			if (channel->sc_creation_callback != NULL)
 				channel->sc_creation_callback(newchannel);