Drivers: hv: vmbus: Implement multi-channel support

Starting with Win8, the host supports multiple sub-channels for a given
device. As in the past, the initial channel offer specifies the device and
is associated with both the type and the instance GUIDs. For performance
critical devices, the host may support multiple sub-channels. The sub-channels
share the same type and instance GUID as the primary channel. The number of
sub-channels offerrred to the guest depends on the number of virtual CPUs
assigned to the guest. The guest can request the creation of these sub-channels
and once created and opened, the guest can distribute the traffic across all
the channels (the primary and the sub-channels). A request sent on a sub-channel
will have the response delivered on the same sub-channel.

At channel (sub-channel) creation we bind the channel interrupt to a CPU and
with this sub-channel support we will be able to spread the interrupt load
of a given device across all available CPUs.

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, 46 insertions, 4 deletions

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 0b122f8..6de6c98 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -116,6 +116,15 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
 	unsigned long flags;
 	int ret, t, err = 0;
 
+	spin_lock_irqsave(&newchannel->sc_lock, flags);
+	if (newchannel->state == CHANNEL_OPEN_STATE) {
+		newchannel->state = CHANNEL_OPENING_STATE;
+	} else {
+		spin_unlock_irqrestore(&newchannel->sc_lock, flags);
+		return -EINVAL;
+	}
+	spin_unlock_irqrestore(&newchannel->sc_lock, flags);
+
 	newchannel->onchannel_callback = onchannelcallback;
 	newchannel->channel_callback_context = context;
 
@@ -216,6 +225,9 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
 	list_del(&open_info->msglistentry);
 	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 
+	if (err == 0)
+		newchannel->state = CHANNEL_OPENED_STATE;
+
 	kfree(open_info);
 	return err;
 
@@ -500,15 +512,14 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle)
 }
 EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl);
 
-/*
- * vmbus_close - Close the specified channel
- */
-void vmbus_close(struct vmbus_channel *channel)
+static void vmbus_close_internal(struct vmbus_channel *channel)
 {
 	struct vmbus_channel_close_channel *msg;
 	int ret;
 	unsigned long flags;
 
+	channel->state = CHANNEL_OPEN_STATE;
+	channel->sc_creation_callback = NULL;
 	/* Stop callback and cancel the timer asap */
 	spin_lock_irqsave(&channel->inbound_lock, flags);
 	channel->onchannel_callback = NULL;
@@ -538,6 +549,37 @@ void vmbus_close(struct vmbus_channel *channel)
 
 
 }
+
+/*
+ * vmbus_close - Close the specified channel
+ */
+void vmbus_close(struct vmbus_channel *channel)
+{
+	struct list_head *cur, *tmp;
+	struct vmbus_channel *cur_channel;
+
+	if (channel->primary_channel != NULL) {
+		/*
+		 * We will only close sub-channels when
+		 * the primary is closed.
+		 */
+		return;
+	}
+	/*
+	 * Close all the sub-channels first and then close the
+	 * primary channel.
+	 */
+	list_for_each_safe(cur, tmp, &channel->sc_list) {
+		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
+		if (cur_channel->state != CHANNEL_OPENED_STATE)
+			continue;
+		vmbus_close_internal(cur_channel);
+	}
+	/*
+	 * Now close the primary.
+	 */
+	vmbus_close_internal(channel);
+}
 EXPORT_SYMBOL_GPL(vmbus_close);
 
 /**