virtio: introduce the consistent-qp feature

In certain usecases related to Linux legacy pinning of flows on queue
pairs, it is desirable that, for a given index, the rx and tx virtio
queue be handled by the same worker. This change introduces a flag for
virtio and tap interfaces that allow such a mapping.
Example with two workers rxq 0 and txq 0 on worker 0
         rxq 1 and txq 1 on worker 1
         txq 2 on main thread

Change-Id: I1b74a4788843fd1d0e8dcb4e9da30e609e088fe3
Signed-off-by: Mohammed Hawari <mohammed@hawari.fr>
Type: improvement

8 files changed, 29 insertions, 15 deletions

diff --git a/src/vnet/devices/tap/cli.c b/src/vnet/devices/tap/cli.c
index 5c676d32d60..5738ef237b6 100644
--- a/src/vnet/devices/tap/cli.c
+++ b/src/vnet/devices/tap/cli.c
@@ -105,6 +105,8 @@ tap_create_command_fn (vlib_main_t * vm, unformat_input_t * input,
 	    args.tap_flags |= TAP_FLAG_PACKED;
 	  else if (unformat (line_input, "in-order"))
 	    args.tap_flags |= TAP_FLAG_IN_ORDER;
+	  else if (unformat (line_input, "consistent-qp"))
+	    args.tap_flags |= TAP_FLAG_CONSISTENT_QP;
 	  else if (unformat (line_input, "hw-addr %U",
 			     unformat_ethernet_address, args.mac_addr.bytes))
 	    args.mac_addr_set = 1;
diff --git a/src/vnet/devices/tap/tap.c b/src/vnet/devices/tap/tap.c
index b0b0a3af13f..bb91200a525 100644
--- a/src/vnet/devices/tap/tap.c
+++ b/src/vnet/devices/tap/tap.c
@@ -212,6 +212,9 @@ tap_create_if (vlib_main_t * vm, tap_create_if_args_t * args)
 	}
     }
 
+  if (args->tap_flags & TAP_FLAG_CONSISTENT_QP)
+    vif->consistent_qp = 1;
+
   /* if namespace is specified, all further netlink messages should be executed
    * after we change our net namespace */
   if (args->host_namespace)
diff --git a/src/vnet/devices/tap/tap.h b/src/vnet/devices/tap/tap.h
index 1df2fb7e1ad..66f5576c5be 100644
--- a/src/vnet/devices/tap/tap.h
+++ b/src/vnet/devices/tap/tap.h
@@ -22,15 +22,16 @@
 #define MIN(x,y) (((x)<(y))?(x):(y))
 #endif
 
-#define foreach_tapv2_flags  \
-  _ (GSO, 0)                 \
-  _ (CSUM_OFFLOAD, 1)        \
-  _ (PERSIST, 2)             \
-  _ (ATTACH, 3)              \
-  _ (TUN, 4)                 \
-  _ (GRO_COALESCE, 5)        \
-  _ (PACKED, 6)              \
-  _ (IN_ORDER, 7)
+#define foreach_tapv2_flags                                                   \
+  _ (GSO, 0)                                                                  \
+  _ (CSUM_OFFLOAD, 1)                                                         \
+  _ (PERSIST, 2)                                                              \
+  _ (ATTACH, 3)                                                               \
+  _ (TUN, 4)                                                                  \
+  _ (GRO_COALESCE, 5)                                                         \
+  _ (PACKED, 6)                                                               \
+  _ (IN_ORDER, 7)                                                             \
+  _ (CONSISTENT_QP, 8)
 
 typedef enum
 {
diff --git a/src/vnet/devices/virtio/cli.c b/src/vnet/devices/virtio/cli.c
index c4364600722..34c74ac91ac 100644
--- a/src/vnet/devices/virtio/cli.c
+++ b/src/vnet/devices/virtio/cli.c
@@ -64,6 +64,8 @@ virtio_pci_create_command_fn (vlib_main_t * vm, unformat_input_t * input,
 	args.bind = VIRTIO_BIND_DEFAULT;
       else if (unformat (line_input, "rss-enabled"))
 	args.rss_enabled = 1;
+      else if (unformat (line_input, "consistent-qp"))
+	args.virtio_flags |= VIRTIO_FLAG_CONSISTENT_QP;
       else
 	return clib_error_return (0, "unknown input `%U'",
 				  format_unformat_error, input);
diff --git a/src/vnet/devices/virtio/pci.c b/src/vnet/devices/virtio/pci.c
index 140cdb94153..9562bdc6369 100644
--- a/src/vnet/devices/virtio/pci.c
+++ b/src/vnet/devices/virtio/pci.c
@@ -1418,9 +1418,10 @@ virtio_pci_create_if (vlib_main_t * vm, virtio_pci_create_if_args_t * args)
   if (args->virtio_flags & VIRTIO_FLAG_PACKED)
     vif->is_packed = 1;
 
-  if ((error =
-       vlib_pci_device_open (vm, (vlib_pci_addr_t *) & vif->pci_addr,
-			     virtio_pci_device_ids, &h)))
+  if (args->virtio_flags & VIRTIO_FLAG_CONSISTENT_QP)
+    vif->consistent_qp = 1;
+  if ((error = vlib_pci_device_open (vm, (vlib_pci_addr_t *) &vif->pci_addr,
+				     virtio_pci_device_ids, &h)))
     {
       args->rv = VNET_API_ERROR_INVALID_INTERFACE;
       args->error =
diff --git a/src/vnet/devices/virtio/pci.h b/src/vnet/devices/virtio/pci.h
index 745ad6fce87..59778533316 100644
--- a/src/vnet/devices/virtio/pci.h
+++ b/src/vnet/devices/virtio/pci.h
@@ -283,7 +283,8 @@ typedef struct _virtio_pci_func
   _ (PACKED, 3)                                                               \
   _ (IN_ORDER, 4)                                                             \
   _ (BUFFERING, 5)                                                            \
-  _ (RSS, 6)
+  _ (RSS, 6)                                                                  \
+  _ (CONSISTENT_QP, 7)
 
 typedef enum
 {
diff --git a/src/vnet/devices/virtio/virtio.c b/src/vnet/devices/virtio/virtio.c
index 840936a43ff..682ec32ceff 100644
--- a/src/vnet/devices/virtio/virtio.c
+++ b/src/vnet/devices/virtio/virtio.c
@@ -294,6 +294,8 @@ virtio_vring_set_tx_queues (vlib_main_t *vm, virtio_if_t *vif)
 {
   vnet_main_t *vnm = vnet_get_main ();
   vnet_virtio_vring_t *vring;
+  uword n_threads = vlib_get_n_threads ();
+  u8 consistent = vif->consistent_qp;
 
   vec_foreach (vring, vif->txq_vrings)
     {
@@ -308,10 +310,11 @@ virtio_vring_set_tx_queues (vlib_main_t *vm, virtio_if_t *vif)
       return;
     }
 
-  for (u32 j = 0; j < vlib_get_n_threads (); j++)
+  for (u32 j = 0; j < n_threads; j++)
     {
       u32 qi = vif->txq_vrings[j % vif->num_txqs].queue_index;
-      vnet_hw_if_tx_queue_assign_thread (vnm, qi, j);
+      vnet_hw_if_tx_queue_assign_thread (vnm, qi,
+					 (j + consistent) % n_threads);
     }
 
   vnet_hw_if_update_runtime_data (vnm, vif->hw_if_index);
diff --git a/src/vnet/devices/virtio/virtio.h b/src/vnet/devices/virtio/virtio.h
index a8e258884a4..fb72051ce45 100644
--- a/src/vnet/devices/virtio/virtio.h
+++ b/src/vnet/devices/virtio/virtio.h
@@ -213,6 +213,7 @@ typedef struct
   };
   const virtio_pci_func_t *virtio_pci_func;
   int is_packed;
+  u8 consistent_qp : 1;
 } virtio_if_t;
 
 typedef struct