Index: head/sys/dev/hyperv/include/hyperv.h
===================================================================
--- head/sys/dev/hyperv/include/hyperv.h
+++ head/sys/dev/hyperv/include/hyperv.h
@@ -471,7 +471,7 @@
 	uint8_t                 reserved[4084];
 
 	/*
-	 * WARNING: Ring data starts here + ring_data_start_offset
+	 * WARNING: Ring data starts here
 	 *  !!! DO NOT place any fields below this !!!
 	 */
 	uint8_t			buffer[0];	/* doubles as interrupt mask */
@@ -491,10 +491,8 @@
 
 typedef struct {
 	hv_vmbus_ring_buffer*	ring_buffer;
-	uint32_t		ring_size;	/* Include the shared header */
 	struct mtx		ring_lock;
 	uint32_t		ring_data_size;	/* ring_size */
-	uint32_t		ring_data_start_offset;
 } hv_vmbus_ring_buffer_info;
 
 typedef void (*hv_vmbus_pfn_channel_callback)(void *context);
Index: head/sys/dev/hyperv/vmbus/hv_ring_buffer.c
===================================================================
--- head/sys/dev/hyperv/vmbus/hv_ring_buffer.c
+++ head/sys/dev/hyperv/vmbus/hv_ring_buffer.c
@@ -286,7 +286,6 @@
 	ring_info->ring_buffer->read_index =
 	    ring_info->ring_buffer->write_index = 0;
 
-	ring_info->ring_size = buffer_len;
 	ring_info->ring_data_size = buffer_len - sizeof(hv_vmbus_ring_buffer);
 
 	mtx_init(&ring_info->ring_lock, "vmbus ring buffer", NULL, MTX_SPIN);