virtio: integrate with new tx infra

Type: improvement

Change-Id: I337ec63d0868f665329d68eadf1744e080b73a0d
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>

1 files changed, 159 insertions, 0 deletions

diff --git a/src/vnet/devices/virtio/virtio_pre_input.c b/src/vnet/devices/virtio/virtio_pre_input.c
new file mode 100644
index 00000000000..ee6e848310d
--- /dev/null
+++ b/src/vnet/devices/virtio/virtio_pre_input.c
@@ -0,0 +1,159 @@
+/*
+ *------------------------------------------------------------------
+ * Copyright (c) 2021 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *------------------------------------------------------------------
+ */
+
+#include <vlib/vlib.h>
+#include <vnet/gso/gro_func.h>
+#include <vnet/interface/tx_queue_funcs.h>
+#include <vnet/devices/virtio/virtio.h>
+#include <vnet/devices/virtio/virtio_inline.h>
+
+static_always_inline uword
+virtio_pre_input_inline (vlib_main_t *vm, virtio_vring_t *txq_vring,
+			 vnet_hw_if_tx_queue_t *txq, u8 packet_coalesce,
+			 u8 packet_buffering)
+{
+  if (txq->shared_queue)
+    {
+      if (clib_spinlock_trylock (&txq_vring->lockp))
+	{
+	  if (virtio_txq_is_scheduled (txq_vring))
+	    return 0;
+	  if (packet_coalesce)
+	    vnet_gro_flow_table_schedule_node_on_dispatcher (
+	      vm, txq, txq_vring->flow_table);
+	  else if (packet_buffering)
+	    virtio_vring_buffering_schedule_node_on_dispatcher (
+	      vm, txq, txq_vring->buffering);
+	  virtio_txq_set_scheduled (txq_vring);
+	  clib_spinlock_unlock (&txq_vring->lockp);
+	}
+    }
+  else
+    {
+      if (packet_coalesce)
+	vnet_gro_flow_table_schedule_node_on_dispatcher (
+	  vm, txq, txq_vring->flow_table);
+      else if (packet_buffering)
+	virtio_vring_buffering_schedule_node_on_dispatcher (
+	  vm, txq, txq_vring->buffering);
+    }
+  return 0;
+}
+
+static uword
+virtio_pre_input (vlib_main_t *vm, vlib_node_runtime_t *node,
+		  vlib_frame_t *frame)
+{
+  virtio_main_t *vim = &virtio_main;
+  vnet_main_t *vnm = vnet_get_main ();
+  virtio_if_t *vif;
+
+  pool_foreach (vif, vim->interfaces)
+    {
+      if (vif->packet_coalesce || vif->packet_buffering)
+	{
+	  virtio_vring_t *txq_vring;
+	  vec_foreach (txq_vring, vif->txq_vrings)
+	    {
+	      vnet_hw_if_tx_queue_t *txq =
+		vnet_hw_if_get_tx_queue (vnm, txq_vring->queue_index);
+	      if (clib_bitmap_get (txq->threads, vm->thread_index) == 1)
+		virtio_pre_input_inline (vm, txq_vring, txq,
+					 vif->packet_coalesce,
+					 vif->packet_buffering);
+	    }
+	}
+    }
+
+  return 0;
+}
+
+/**
+ * virtio interfaces support packet coalescing and buffering which
+ * depends on timer expiry to flush the stored packets periodically.
+ * Previously, virtio input node checked timer expiry and scheduled
+ * tx queue accordingly.
+ *
+ * In poll mode, timer expiry was handled naturally, as input node
+ * runs periodically. In interrupt mode, virtio input node was dependent
+ * on the interrupts send from backend. Stored packets could starve,
+ * if there would not be interrupts to input node.
+ *
+ * This problem had been solved through a dedicated process node which
+ * periodically sends interrupt to virtio input node given coalescing
+ * or buffering feature were enabled on an interface.
+ *
+ * But that approach worked with following limitations:
+ * 1) Each VPP thread should have (atleast) 1 rx queue of an interface
+ * (with buffering enabled). And rxqs and txqs should be placed on the
+ * same thread.
+ *
+ * New design provides solution to above problem(s) without any limitation
+ * through (dedicated) pre-input node running on each VPP thread when
+ * atleast 1 virtio interface is enabled with coalescing or buffering.
+ */
+VLIB_REGISTER_NODE (virtio_pre_input_node) = {
+  .function = virtio_pre_input,
+  .type = VLIB_NODE_TYPE_PRE_INPUT,
+  .name = "virtio-pre-input",
+  .state = VLIB_NODE_STATE_DISABLED,
+};
+
+void
+virtio_pre_input_node_enable (vlib_main_t *vm, virtio_if_t *vif)
+{
+  virtio_main_t *vim = &virtio_main;
+  if (vif->packet_coalesce || vif->packet_buffering)
+    {
+      vim->gro_or_buffering_if_count++;
+      if (vim->gro_or_buffering_if_count == 1)
+	{
+	  foreach_vlib_main ()
+	    {
+	      vlib_node_set_state (this_vlib_main, virtio_pre_input_node.index,
+				   VLIB_NODE_STATE_POLLING);
+	    }
+	}
+    }
+}
+
+void
+virtio_pre_input_node_disable (vlib_main_t *vm, virtio_if_t *vif)
+{
+  virtio_main_t *vim = &virtio_main;
+  if (vif->packet_coalesce || vif->packet_buffering)
+    {
+      if (vim->gro_or_buffering_if_count > 0)
+	vim->gro_or_buffering_if_count--;
+      if (vim->gro_or_buffering_if_count == 0)
+	{
+	  foreach_vlib_main ()
+	    {
+	      vlib_node_set_state (this_vlib_main, virtio_pre_input_node.index,
+				   VLIB_NODE_STATE_DISABLED);
+	    }
+	}
+    }
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */