Drivers: hv: Update the ring buffer structure to match win8 functionality

Update the ringbuffer structure to support win8 functionality.

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, 21 insertions, 7 deletions

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index b097bf9d9328..2b5480126394 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -325,14 +325,28 @@ struct hv_ring_buffer {
 
         u32 interrupt_mask;
 
-        /* Pad it to PAGE_SIZE so that data starts on page boundary */
-        u8      reserved[4084];
-
-        /* NOTE:
-         * The interrupt_mask field is used only for channels but since our
-         * vmbus connection also uses this data structure and its data starts
-         * here, we commented out this field.
+        /*
+         * Win8 uses some of the reserved bits to implement
+         * interrupt driven flow management. On the send side
+         * we can request that the receiver interrupt the sender
+         * when the ring transitions from being full to being able
+         * to handle a message of size "pending_send_sz".
+         *
+         * Add necessary state for this enhancement.
          */
+        u32 pending_send_sz;
+
+        u32 reserved1[12];
+
+        union {
+                struct {
+                        u32 feat_pending_send_sz:1;
+                };
+                u32 value;
+        } feature_bits;
+
+        /* Pad it to PAGE_SIZE so that data starts on page boundary */
+        u8      reserved2[4028];
 
         /*
          * Ring data starts here + RingDataStartOffset