[PATCH 2/2] xennet: fix TX doorbell coalescing — More flag dropped at NBL boundaries

[david ambu <david.preetham@xxxxxxxxxx>]

  __TransmitterSendNetBufferList computed the More flag as
  (NET_BUFFER_NEXT_NB(NetBuffer) != NULL), which only looks at remaining
  NET_BUFFERs within the current NBL. This evaluates to FALSE for the last
  NB of every NBL, even when the outer loop in TransmitterSendNetBufferLists
  still has additional NBLs to submit in the same batch.

Assisted-by: ClaudeCode:claude-opus-4.8
Signed-off-by: david ambu <david.preetham@xxxxxxxxxx>
---
 src/xennet/transmitter.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/xennet/transmitter.c b/src/xennet/transmitter.c
index 4bb82bc..e17d89f 100644
--- a/src/xennet/transmitter.c
+++ b/src/xennet/transmitter.c
@@ -288,7 +288,8 @@ __TransmitterHash(
 static VOID
 __TransmitterSendNetBufferList(
     IN  PXENNET_TRANSMITTER     Transmitter,
-    IN  PNET_BUFFER_LIST        NetBufferList
+    IN  PNET_BUFFER_LIST        NetBufferList,
+    IN  BOOLEAN                 MoreNbls
     )
 {
     PNET_BUFFER_LIST_RESERVED   ListReserved;
@@ -338,7 +339,7 @@ __TransmitterSendNetBufferList(
                                 MaximumSegmentSize,
                                 TagControlInformation,
                                 &Hash,
-                                (NetBufferListNext != NULL) ? TRUE : FALSE,
+                                (NetBufferListNext != NULL || MoreNbls) ? TRUE 
: FALSE,
                                 Cookie);
         }
         else
@@ -384,7 +385,9 @@ TransmitterSendNetBufferLists(
         ListNext = NET_BUFFER_LIST_NEXT_NBL(NetBufferList);
         NET_BUFFER_LIST_NEXT_NBL(NetBufferList) = NULL;
 
-        __TransmitterSendNetBufferList(Transmitter, NetBufferList);
+        __TransmitterSendNetBufferList(Transmitter,
+                                       NetBufferList,
+                                       (ListNext != NULL) ? TRUE : FALSE);
 
         NetBufferList = ListNext;
     }
-- 
2.51.0.windows.1