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Commit 3a28fa35 authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
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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: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d3ba720d

drivers/hv/channel_mgmt.c

+40 −1
Original line number Diff line number Diff line
@@ -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);

drivers/hv/connection.c

+23 −1
Original line number Diff line number Diff line
@@ -234,6 +234,28 @@ int vmbus_connect(void) 
	return ret;

}



/*

 * Map the given relid to the corresponding channel based on the

 * per-cpu list of channels that have been affinitized to this CPU.

 * This will be used in the channel callback path as we can do this

 * mapping in a lock-free fashion.

 */

static struct vmbus_channel *pcpu_relid2channel(u32 relid)

{

	struct vmbus_channel *channel;

	struct vmbus_channel *found_channel  = NULL;

	int cpu = smp_processor_id();

	struct list_head *pcpu_head = &hv_context.percpu_list[cpu];



	list_for_each_entry(channel, pcpu_head, percpu_list) {

		if (channel->offermsg.child_relid == relid) {

			found_channel = channel;

			break;

		}

	}



	return found_channel;

}



/*

 * relid2channel - Get the channel object given its
@@ -285,7 +307,7 @@ static void process_chn_event(u32 relid) 
	 * Find the channel based on this relid and invokes the

	 * channel callback to process the event

	 */

	channel = relid2channel(relid);

	channel = pcpu_relid2channel(relid);



	if (!channel) {

		pr_err("channel not found for relid - %u\n", relid);

drivers/hv/hv.c

+2 −0
Original line number Diff line number Diff line
@@ -383,6 +383,8 @@ void hv_synic_init(void *arg) 
	 */

	rdmsrl(HV_X64_MSR_VP_INDEX, vp_index);

	hv_context.vp_index[cpu] = (u32)vp_index;



	INIT_LIST_HEAD(&hv_context.percpu_list[cpu]);

	return;

}

drivers/hv/hyperv_vmbus.h

+5 −0
Original line number Diff line number Diff line
@@ -510,6 +510,11 @@ struct hv_context { 
	 * basis.

	 */

	struct tasklet_struct *event_dpc[NR_CPUS];

	/*

	 * To optimize the mapping of relid to channel, maintain

	 * per-cpu list of the channels based on their CPU affinity.

	 */

	struct list_head percpu_list[NR_CPUS];

};



extern struct hv_context hv_context;

include/linux/hyperv.h

+5 −0
Original line number Diff line number Diff line
@@ -734,6 +734,11 @@ struct vmbus_channel { 
	 * Support per-channel state for use by vmbus drivers.

	 */

	void *per_channel_state;

	/*

	 * To support per-cpu lookup mapping of relid to channel,

	 * link up channels based on their CPU affinity.

	 */

	struct list_head percpu_list;

};



static inline void set_channel_read_state(struct vmbus_channel *c, bool state)