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Commit f878f3d5 authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
Browse files

Drivers: hv: Optimize signaling in the read path 



Now that we have the infratructure for correctly determining when we
should signal the host; optimize the signaling on the read side -
signaling the guest from the host.

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 7ae3e035

drivers/hv/connection.c

+25 −3
Original line number Diff line number Diff line
@@ -212,6 +212,9 @@ static void process_chn_event(u32 relid) 
{

	struct vmbus_channel *channel;

	unsigned long flags;

	void *arg;

	bool read_state;

	u32 bytes_to_read;



	/*

	 * Find the channel based on this relid and invokes the
@@ -234,10 +237,29 @@ static void process_chn_event(u32 relid) 
	 */



	spin_lock_irqsave(&channel->inbound_lock, flags);

	if (channel->onchannel_callback != NULL)

		channel->onchannel_callback(channel->channel_callback_context);

	else

	if (channel->onchannel_callback != NULL) {

		arg = channel->channel_callback_context;

		read_state = channel->batched_reading;

		/*

		 * This callback reads the messages sent by the host.

		 * We can optimize host to guest signaling by ensuring:

		 * 1. While reading the channel, we disable interrupts from

		 *    host.

		 * 2. Ensure that we process all posted messages from the host

		 *    before returning from this callback.

		 * 3. Once we return, enable signaling from the host. Once this

		 *    state is set we check to see if additional packets are

		 *    available to read. In this case we repeat the process.

		 */



		do {

			hv_begin_read(&channel->inbound);

			channel->onchannel_callback(arg);

			bytes_to_read = hv_end_read(&channel->inbound);

		} while (read_state && (bytes_to_read != 0));

	} else {

		pr_err("no channel callback for relid - %u\n", relid);

	}



	spin_unlock_irqrestore(&channel->inbound_lock, flags);

}