From 82569141943b1d04037282082cc47eb2b1c0556a Mon Sep 17 00:00:00 2001
From: Mohammed Hawari <mohammed@hawari.fr>
Date: Wed, 6 Nov 2024 17:13:02 +0100
Subject: dev: introduce consistent_qp feature

For some devices, queues are organized as pairs (rx/tx). In this case,
it is desirable that a worker receives packet and send packets for the
same pair. This patch enables this by assigning txq to workers first
and ending with main.

Change-Id: I3de4afbf74a265d5275c6a5d9a905b51dd661b22
Type: feature
Signed-off-by: Mohammed Hawari <mohammed@hawari.fr>
---
 src/vnet/dev/api.c    | 2 ++
 src/vnet/dev/dev.api  | 1 +
 src/vnet/dev/dev.h    | 1 +
 src/vnet/dev/format.c | 4 ++--
 src/vnet/dev/port.c   | 8 ++++++--
 src/vnet/dev/types.h  | 3 ++-
 6 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/vnet/dev/api.c b/src/vnet/dev/api.c
index 0f4bd0b653e..48ceccf3b6c 100644
--- a/src/vnet/dev/api.c
+++ b/src/vnet/dev/api.c
@@ -238,6 +238,8 @@ vnet_dev_api_create_port_if (vlib_main_t *vm,
 
   clib_memcpy (port->intf.name, args->intf_name, sizeof (port->intf.name));
   port->intf.default_is_intr_mode = default_is_intr_mode;
+  port->intf.consistent_qp =
+    (args->flags.n & VNET_DEV_PORT_F_CONSISTENT_QP) != 0;
 
   rv = vnet_dev_process_call_port_op (vm, port, vnet_dev_port_if_create);
   args->sw_if_index = (rv == VNET_DEV_OK) ? port->intf.sw_if_index : ~0;
diff --git a/src/vnet/dev/dev.api b/src/vnet/dev/dev.api
index 552b778949b..423d0ee8505 100644
--- a/src/vnet/dev/dev.api
+++ b/src/vnet/dev/dev.api
@@ -12,6 +12,7 @@ enumflag dev_flags : u32
 enumflag dev_port_flags : u32
 {
   VL_API_DEV_PORT_FLAG_INTERRUPT_MODE = 0x1,
+  VL_API_DEV_PORT_FLAG_CONSISTENT_QP = 0x2,
 };
 
 autoendian define dev_attach
diff --git a/src/vnet/dev/dev.h b/src/vnet/dev/dev.h
index 57c6d09d181..76ff4f55b71 100644
--- a/src/vnet/dev/dev.h
+++ b/src/vnet/dev/dev.h
@@ -356,6 +356,7 @@ typedef struct vnet_dev_port
     u8 feature_arc : 1;
     u8 redirect_to_node : 1;
     u8 default_is_intr_mode : 1;
+    u8 consistent_qp : 1;
     u32 tx_node_index;
     u32 hw_if_index;
     u32 sw_if_index;
diff --git a/src/vnet/dev/format.c b/src/vnet/dev/format.c
index bde245cafee..fb46fcc47bc 100644
--- a/src/vnet/dev/format.c
+++ b/src/vnet/dev/format.c
@@ -319,7 +319,7 @@ unformat_vnet_dev_port_flags (unformat_input_t *input, va_list *args)
 #undef _
   };
   u64 flag_values[] = {
-#define _(b, n, d) 1ull << (b)
+#define _(b, n, d) 1ull << (b),
     foreach_vnet_dev_port_flag
 #undef _
   };
@@ -395,7 +395,7 @@ format_vnet_dev_port_flags (u8 *s, va_list *args)
 #undef _
   };
   u64 flag_values[] = {
-#define _(b, n, d) 1ull << (b)
+#define _(b, n, d) 1ull << (b),
     foreach_vnet_dev_port_flag
 #undef _
   };
diff --git a/src/vnet/dev/port.c b/src/vnet/dev/port.c
index 7126ceed731..5bd4edf05c1 100644
--- a/src/vnet/dev/port.c
+++ b/src/vnet/dev/port.c
@@ -520,6 +520,7 @@ vnet_dev_port_if_create (vlib_main_t *vm, vnet_dev_port_t *port)
   vnet_dev_instance_t *di;
   vnet_dev_rv_t rv;
   u16 ti = 0;
+  u8 is_consistent_qp = port->intf.consistent_qp;
 
   if (port->intf.name[0] == 0)
     {
@@ -556,9 +557,12 @@ vnet_dev_port_if_create (vlib_main_t *vm, vnet_dev_port_t *port)
 
   foreach_vnet_dev_port_tx_queue (q, port)
     {
-      q->assigned_threads = clib_bitmap_set (q->assigned_threads, ti, 1);
+      /* if consistent_qp is enabled, we start by assigning queues to workers
+       * and we end with main */
+      u16 real_ti = (ti + is_consistent_qp) % n_threads;
+      q->assigned_threads = clib_bitmap_set (q->assigned_threads, real_ti, 1);
       log_debug (dev, "port %u tx queue %u assigned to thread %u",
-		 port->port_id, q->queue_id, ti);
+		 port->port_id, q->queue_id, real_ti);
       if (++ti >= n_threads)
 	break;
     }
diff --git a/src/vnet/dev/types.h b/src/vnet/dev/types.h
index 006d18e5bc5..24799ac8138 100644
--- a/src/vnet/dev/types.h
+++ b/src/vnet/dev/types.h
@@ -50,7 +50,8 @@ typedef union
 
 /* do not change bit assignments - API dependency */
 #define foreach_vnet_dev_port_flag                                            \
-  _ (0, INTERRUPT_MODE, "enable interrupt mode")
+  _ (0, INTERRUPT_MODE, "enable interrupt mode")                              \
+  _ (1, CONSISTENT_QP, "consistent queue pairs")
 
 typedef union
 {
-- 
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