vmbus: more host signalling avoidance

Don't signal host if it has disabled interrupts for that
ring buffer. Check the feature bit to see if host supports
pending send size flag.

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>

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index b0f79526b86af02292db6c16fe16b8fb050fa1d8..741daa6e2fc7788acf4c5a5fc821e198d30b8fd9 100644 (file)
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -396,7 +396,6 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
 {
        struct hv_ring_buffer_info *rbi = &channel->inbound;
        u32 orig_write_sz = hv_get_bytes_to_write(rbi);
-       u32 pending_sz;
 
        /*
         * Make sure all reads are done before we update the read index since
@@ -419,15 +418,27 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
         */
        virt_mb();
 
-       pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
-       /* If the other end is not blocked on write don't bother. */
-       if (pending_sz == 0)
+       /* If host has disabled notifications then skip */
+       if (rbi->ring_buffer->interrupt_mask)
                return;
 
-       if (hv_get_bytes_to_write(rbi) < pending_sz)
-               return;
+       if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) {
+               u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
 
-       if (orig_write_sz < pending_sz)
-               vmbus_setevent(channel);
+               /*
+                * If there was space before we began iteration,
+                * then host was not blocked. Also handles case where
+                * pending_sz is zero then host has nothing pending
+                * and does not need to be signaled.
+                */
+               if (orig_write_sz > pending_sz)
+                       return;
+
+               /* If pending write will not fit, don't give false hope. */
+               if (hv_get_bytes_to_write(rbi) < pending_sz)
+                       return;
+       }
+
+       vmbus_setevent(channel);
 }
 EXPORT_SYMBOL_GPL(hv_pkt_iter_close);