1 files changed, 25 insertions, 19 deletions

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 08043da1a61c..cd49cb17eb7f 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -66,21 +66,25 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
  *	   once the ring buffer is empty, it will clear the
  *	   interrupt_mask and re-check to see if new data has
  *	   arrived.
+ *
+ * KYS: Oct. 30, 2016:
+ * It looks like Windows hosts have logic to deal with DOS attacks that
+ * can be triggered if it receives interrupts when it is not expecting
+ * the interrupt. The host expects interrupts only when the ring
+ * transitions from empty to non-empty (or full to non full on the guest
+ * to host ring).
+ * So, base the signaling decision solely on the ring state until the
+ * host logic is fixed.
  */
 
-static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi,
-			      enum hv_signal_policy policy)
+static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel,
+			       bool kick_q)
 {
+	struct hv_ring_buffer_info *rbi = &channel->outbound;
+
 	virt_mb();
 	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
-		return false;
-
-	/*
-	 * When the client wants to control signaling,
-	 * we only honour the host interrupt mask.
-	 */
-	if (policy == HV_SIGNAL_POLICY_EXPLICIT)
-		return true;
+		return;
 
 	/* check interrupt_mask before read_index */
 	virt_rmb();
@@ -89,9 +93,9 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi,
 	 * ring transitions from being empty to non-empty.
 	 */
 	if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
-		return true;
+		vmbus_setevent(channel);
 
-	return false;
+	return;
 }
 
 /* Get the next write location for the specified ring buffer. */
@@ -280,9 +284,9 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 }
 
 /* Write to the ring buffer. */
-int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
-		    struct kvec *kv_list, u32 kv_count, bool *signal, bool lock,
-		    enum hv_signal_policy policy)
+int hv_ringbuffer_write(struct vmbus_channel *channel,
+		    struct kvec *kv_list, u32 kv_count, bool lock,
+		    bool kick_q)
 {
 	int i = 0;
 	u32 bytes_avail_towrite;
@@ -292,6 +296,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 	u32 old_write;
 	u64 prev_indices = 0;
 	unsigned long flags = 0;
+	struct hv_ring_buffer_info *outring_info = &channel->outbound;
 
 	for (i = 0; i < kv_count; i++)
 		totalbytes_towrite += kv_list[i].iov_len;
@@ -344,13 +349,13 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 	if (lock)
 		spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 
-	*signal = hv_need_to_signal(old_write, outring_info, policy);
+	hv_signal_on_write(old_write, channel, kick_q);
 	return 0;
 }
 
-int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
+int hv_ringbuffer_read(struct vmbus_channel *channel,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
-		       u64 *requestid, bool *signal, bool raw)
+		       u64 *requestid, bool raw)
 {
 	u32 bytes_avail_toread;
 	u32 next_read_location = 0;
@@ -359,6 +364,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 	u32 offset;
 	u32 packetlen;
 	int ret = 0;
+	struct hv_ring_buffer_info *inring_info = &channel->inbound;
 
 	if (buflen <= 0)
 		return -EINVAL;
@@ -416,7 +422,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 	/* Update the read index */
 	hv_set_next_read_location(inring_info, next_read_location);
 
-	*signal = hv_need_to_signal_on_read(inring_info);
+	hv_signal_on_read(channel);
 
 	return ret;
 }