vmbus: add direct isr callback mode

Change the simple boolean batched_reading into a tri-value.
For future NAPI support in netvsc driver, the callback needs to
occur directly in interrupt handler.

Batched mode is also changed to disable host interrupts immediately
in interrupt routine (to avoid unnecessary host signals), and the
tasklet is rescheduled if more data is detected.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 14 deletions

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 69afc9337c0d..e5aac5c051f7 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -748,19 +748,21 @@ struct vmbus_channel {
 	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.
+	 * A channel can be marked for one of three modes of reading:
+	 *   BATCHED - callback called from taslket and should read
+	 *            channel until empty. Interrupts from the host
+	 *            are masked while read is in process (default).
+	 *   DIRECT - callback called from tasklet (softirq).
+	 *   ISR - callback called in interrupt context and must
+	 *         invoke its own deferred processing.
+	 *         Host interrupts are disabled and must be re-enabled
+	 *         when ring is empty.
 	 */
-
-	bool batched_reading;
+	enum hv_callback_mode {
+		HV_CALL_BATCHED,
+		HV_CALL_DIRECT,
+		HV_CALL_ISR
+	} callback_mode;
 
 	bool is_dedicated_interrupt;
 	struct hv_input_signal_event_buffer sig_buf;
@@ -910,9 +912,10 @@ static inline void set_channel_affinity_state(struct vmbus_channel *c,
 	c->affinity_policy = policy;
 }
 
-static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
+static inline void set_channel_read_mode(struct vmbus_channel *c,
+					enum hv_callback_mode mode)
 {
-	c->batched_reading = state;
+	c->callback_mode = mode;
 }
 
 static inline void set_per_channel_state(struct vmbus_channel *c, void *s)