Drivers: hv: Add state to manage batched reading

For the "read" side signaling optimization, the reader has to completely
drain the queue before exiting. Add state to manage this "batched"
reading.

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>

2 files changed, 27 insertions, 0 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 2f84c5cff8d4..7bf59177aaf8 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -275,6 +275,13 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
                 return;
         }
 
+        /*
+         * By default we setup state to enable batched
+         * reading. A specific service can choose to
+         * disable this prior to opening the channel.
+         */
+        newchannel->batched_reading = true;
+
         memcpy(&newchannel->offermsg, offer,
                sizeof(struct vmbus_channel_offer_channel));
         newchannel->monitor_grp = (u8)offer->monitorid / 32;
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index e73b852156b1..1ffe84de6c55 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -882,8 +882,28 @@ struct vmbus_channel {
 
         void (*onchannel_callback)(void *context);
         void *channel_callback_context;
+
+        /*
+         * A channel can be marked for efficient (batched)
+         * reading:
+         * If batched_reading is set to "true", we read until the
+         * channel is empty and hold off interrupts from the host
+         * during the entire read process.
+         * If batched_reading is set to "false", the client is not
+         * going to perform batched reading.
+         *
+         * By default we will enable batched reading; specific
+         * drivers that don't want this behavior can turn it off.
+         */
+
+        bool batched_reading;
 };
 
+static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
+{
+        c->batched_reading = state;
+}
+
 void vmbus_onmessage(void *context);
 
 int vmbus_request_offers(void);