nfp: split out common control message handling code

BPF's control message handler seems like a good base to built
on for request-reply control messages.  Split it out to allow
for reuse.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/Makefile

@@ -15,6 +15,7 @@ nfp-objs := \
 	    nfpcore/nfp_resource.o \
 	    nfpcore/nfp_rtsym.o \
 	    nfpcore/nfp_target.o \
+	    ccm.o \
 	    nfp_asm.o \
 	    nfp_app.o \
 	    nfp_app_nic.o \

drivers/net/ethernet/netronome/nfp/bpf/cmsg.c

@@ -6,48 +6,13 @@
 #include <linux/bug.h>
 #include <linux/jiffies.h>
 #include <linux/skbuff.h>
-#include <linux/wait.h>
 
+#include "../ccm.h"
 #include "../nfp_app.h"
 #include "../nfp_net.h"
 #include "fw.h"
 #include "main.h"
 
-#define NFP_BPF_TAG_ALLOC_SPAN	(U16_MAX / 4)
-
-static bool nfp_bpf_all_tags_busy(struct nfp_app_bpf *bpf)
-{
-	u16 used_tags;
-
-	used_tags = bpf->tag_alloc_next - bpf->tag_alloc_last;
-
-	return used_tags > NFP_BPF_TAG_ALLOC_SPAN;
-}
-
-static int nfp_bpf_alloc_tag(struct nfp_app_bpf *bpf)
-{
-	/* All FW communication for BPF is request-reply.  To make sure we
-	 * don't reuse the message ID too early after timeout - limit the
-	 * number of requests in flight.
-	 */
-	if (nfp_bpf_all_tags_busy(bpf)) {
-		cmsg_warn(bpf, "all FW request contexts busy!\n");
-		return -EAGAIN;
-	}
-
-	WARN_ON(__test_and_set_bit(bpf->tag_alloc_next, bpf->tag_allocator));
-	return bpf->tag_alloc_next++;
-}
-
-static void nfp_bpf_free_tag(struct nfp_app_bpf *bpf, u16 tag)
-{
-	WARN_ON(!__test_and_clear_bit(tag, bpf->tag_allocator));
-
-	while (!test_bit(bpf->tag_alloc_last, bpf->tag_allocator) &&
-	       bpf->tag_alloc_last != bpf->tag_alloc_next)
-		bpf->tag_alloc_last++;
-}
-
 static struct sk_buff *
 nfp_bpf_cmsg_alloc(struct nfp_app_bpf *bpf, unsigned int size)
 {
@@ -87,149 +52,6 @@ nfp_bpf_cmsg_map_reply_size(struct nfp_app_bpf *bpf, unsigned int n)
 	return size;
 }
 
-static u8 nfp_bpf_cmsg_get_type(struct sk_buff *skb)
-{
-	struct cmsg_hdr *hdr;
-
-	hdr = (struct cmsg_hdr *)skb->data;
-
-	return hdr->type;
-}
-
-static unsigned int nfp_bpf_cmsg_get_tag(struct sk_buff *skb)
-{
-	struct cmsg_hdr *hdr;
-
-	hdr = (struct cmsg_hdr *)skb->data;
-
-	return be16_to_cpu(hdr->tag);
-}
-
-static struct sk_buff *__nfp_bpf_reply(struct nfp_app_bpf *bpf, u16 tag)
-{
-	unsigned int msg_tag;
-	struct sk_buff *skb;
-
-	skb_queue_walk(&bpf->cmsg_replies, skb) {
-		msg_tag = nfp_bpf_cmsg_get_tag(skb);
-		if (msg_tag == tag) {
-			nfp_bpf_free_tag(bpf, tag);
-			__skb_unlink(skb, &bpf->cmsg_replies);
-			return skb;
-		}
-	}
-
-	return NULL;
-}
-
-static struct sk_buff *nfp_bpf_reply(struct nfp_app_bpf *bpf, u16 tag)
-{
-	struct sk_buff *skb;
-
-	nfp_ctrl_lock(bpf->app->ctrl);
-	skb = __nfp_bpf_reply(bpf, tag);
-	nfp_ctrl_unlock(bpf->app->ctrl);
-
-	return skb;
-}
-
-static struct sk_buff *nfp_bpf_reply_drop_tag(struct nfp_app_bpf *bpf, u16 tag)
-{
-	struct sk_buff *skb;
-
-	nfp_ctrl_lock(bpf->app->ctrl);
-	skb = __nfp_bpf_reply(bpf, tag);
-	if (!skb)
-		nfp_bpf_free_tag(bpf, tag);
-	nfp_ctrl_unlock(bpf->app->ctrl);
-
-	return skb;
-}
-
-static struct sk_buff *
-nfp_bpf_cmsg_wait_reply(struct nfp_app_bpf *bpf, enum nfp_bpf_cmsg_type type,
-			int tag)
-{
-	struct sk_buff *skb;
-	int i, err;
-
-	for (i = 0; i < 50; i++) {
-		udelay(4);
-		skb = nfp_bpf_reply(bpf, tag);
-		if (skb)
-			return skb;
-	}
-
-	err = wait_event_interruptible_timeout(bpf->cmsg_wq,
-					       skb = nfp_bpf_reply(bpf, tag),
-					       msecs_to_jiffies(5000));
-	/* We didn't get a response - try last time and atomically drop
-	 * the tag even if no response is matched.
-	 */
-	if (!skb)
-		skb = nfp_bpf_reply_drop_tag(bpf, tag);
-	if (err < 0) {
-		cmsg_warn(bpf, "%s waiting for response to 0x%02x: %d\n",
-			  err == ERESTARTSYS ? "interrupted" : "error",
-			  type, err);
-		return ERR_PTR(err);
-	}
-	if (!skb) {
-		cmsg_warn(bpf, "timeout waiting for response to 0x%02x\n",
-			  type);
-		return ERR_PTR(-ETIMEDOUT);
-	}
-
-	return skb;
-}
-
-static struct sk_buff *
-nfp_bpf_cmsg_communicate(struct nfp_app_bpf *bpf, struct sk_buff *skb,
-			 enum nfp_bpf_cmsg_type type, unsigned int reply_size)
-{
-	struct cmsg_hdr *hdr;
-	int tag;
-
-	nfp_ctrl_lock(bpf->app->ctrl);
-	tag = nfp_bpf_alloc_tag(bpf);
-	if (tag < 0) {
-		nfp_ctrl_unlock(bpf->app->ctrl);
-		dev_kfree_skb_any(skb);
-		return ERR_PTR(tag);
-	}
-
-	hdr = (void *)skb->data;
-	hdr->ver = CMSG_MAP_ABI_VERSION;
-	hdr->type = type;
-	hdr->tag = cpu_to_be16(tag);
-
-	__nfp_app_ctrl_tx(bpf->app, skb);
-
-	nfp_ctrl_unlock(bpf->app->ctrl);
-
-	skb = nfp_bpf_cmsg_wait_reply(bpf, type, tag);
-	if (IS_ERR(skb))
-		return skb;
-
-	hdr = (struct cmsg_hdr *)skb->data;
-	if (hdr->type != __CMSG_REPLY(type)) {
-		cmsg_warn(bpf, "cmsg drop - wrong type 0x%02x != 0x%02lx!\n",
-			  hdr->type, __CMSG_REPLY(type));
-		goto err_free;
-	}
-	/* 0 reply_size means caller will do the validation */
-	if (reply_size && skb->len != reply_size) {
-		cmsg_warn(bpf, "cmsg drop - type 0x%02x wrong size %d != %d!\n",
-			  type, skb->len, reply_size);
-		goto err_free;
-	}
-
-	return skb;
-err_free:
-	dev_kfree_skb_any(skb);
-	return ERR_PTR(-EIO);
-}
-
 static int
 nfp_bpf_ctrl_rc_to_errno(struct nfp_app_bpf *bpf,
 			 struct cmsg_reply_map_simple *reply)
@@ -275,7 +97,7 @@ nfp_bpf_ctrl_alloc_map(struct nfp_app_bpf *bpf, struct bpf_map *map)
 	req->map_type = cpu_to_be32(map->map_type);
 	req->map_flags = 0;
 
-	skb = nfp_bpf_cmsg_communicate(bpf, skb, CMSG_TYPE_MAP_ALLOC,
+	skb = nfp_ccm_communicate(&bpf->ccm, skb, NFP_CCM_TYPE_BPF_MAP_ALLOC,
 				  sizeof(*reply));
 	if (IS_ERR(skb))
 		return PTR_ERR(skb);
@@ -310,7 +132,7 @@ void nfp_bpf_ctrl_free_map(struct nfp_app_bpf *bpf, struct nfp_bpf_map *nfp_map)
 	req = (void *)skb->data;
 	req->tid = cpu_to_be32(nfp_map->tid);
 
-	skb = nfp_bpf_cmsg_communicate(bpf, skb, CMSG_TYPE_MAP_FREE,
+	skb = nfp_ccm_communicate(&bpf->ccm, skb, NFP_CCM_TYPE_BPF_MAP_FREE,
 				  sizeof(*reply));
 	if (IS_ERR(skb)) {
 		cmsg_warn(bpf, "leaking map - I/O error\n");
@@ -354,8 +176,7 @@ nfp_bpf_ctrl_reply_val(struct nfp_app_bpf *bpf, struct cmsg_reply_map_op *reply,
 }
 
 static int
-nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap,
-		      enum nfp_bpf_cmsg_type op,
+nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap, enum nfp_ccm_type op,
 		      u8 *key, u8 *value, u64 flags, u8 *out_key, u8 *out_value)
 {
 	struct nfp_bpf_map *nfp_map = offmap->dev_priv;
@@ -386,7 +207,7 @@ nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap,
 		memcpy(nfp_bpf_ctrl_req_val(bpf, req, 0), value,
 		       map->value_size);
 
-	skb = nfp_bpf_cmsg_communicate(bpf, skb, op,
+	skb = nfp_ccm_communicate(&bpf->ccm, skb, op,
 				  nfp_bpf_cmsg_map_reply_size(bpf, 1));
 	if (IS_ERR(skb))
 		return PTR_ERR(skb);
@@ -415,34 +236,34 @@ nfp_bpf_ctrl_entry_op(struct bpf_offloaded_map *offmap,
 int nfp_bpf_ctrl_update_entry(struct bpf_offloaded_map *offmap,
 			      void *key, void *value, u64 flags)
 {
-	return nfp_bpf_ctrl_entry_op(offmap, CMSG_TYPE_MAP_UPDATE,
+	return nfp_bpf_ctrl_entry_op(offmap, NFP_CCM_TYPE_BPF_MAP_UPDATE,
 				     key, value, flags, NULL, NULL);
 }
 
 int nfp_bpf_ctrl_del_entry(struct bpf_offloaded_map *offmap, void *key)
 {
-	return nfp_bpf_ctrl_entry_op(offmap, CMSG_TYPE_MAP_DELETE,
+	return nfp_bpf_ctrl_entry_op(offmap, NFP_CCM_TYPE_BPF_MAP_DELETE,
 				     key, NULL, 0, NULL, NULL);
 }
 
 int nfp_bpf_ctrl_lookup_entry(struct bpf_offloaded_map *offmap,
 			      void *key, void *value)
 {
-	return nfp_bpf_ctrl_entry_op(offmap, CMSG_TYPE_MAP_LOOKUP,
+	return nfp_bpf_ctrl_entry_op(offmap, NFP_CCM_TYPE_BPF_MAP_LOOKUP,
 				     key, NULL, 0, NULL, value);
 }
 
 int nfp_bpf_ctrl_getfirst_entry(struct bpf_offloaded_map *offmap,
 				void *next_key)
 {
-	return nfp_bpf_ctrl_entry_op(offmap, CMSG_TYPE_MAP_GETFIRST,
+	return nfp_bpf_ctrl_entry_op(offmap, NFP_CCM_TYPE_BPF_MAP_GETFIRST,
 				     NULL, NULL, 0, next_key, NULL);
 }
 
 int nfp_bpf_ctrl_getnext_entry(struct bpf_offloaded_map *offmap,
 			       void *key, void *next_key)
 {
-	return nfp_bpf_ctrl_entry_op(offmap, CMSG_TYPE_MAP_GETNEXT,
+	return nfp_bpf_ctrl_entry_op(offmap, NFP_CCM_TYPE_BPF_MAP_GETNEXT,
 				     key, NULL, 0, next_key, NULL);
 }
 
@@ -456,54 +277,35 @@ unsigned int nfp_bpf_ctrl_cmsg_mtu(struct nfp_app_bpf *bpf)
 void nfp_bpf_ctrl_msg_rx(struct nfp_app *app, struct sk_buff *skb)
 {
 	struct nfp_app_bpf *bpf = app->priv;
-	unsigned int tag;
 
 	if (unlikely(skb->len < sizeof(struct cmsg_reply_map_simple))) {
 		cmsg_warn(bpf, "cmsg drop - too short %d!\n", skb->len);
-		goto err_free;
+		dev_kfree_skb_any(skb);
+		return;
 	}
 
-	if (nfp_bpf_cmsg_get_type(skb) == CMSG_TYPE_BPF_EVENT) {
+	if (nfp_ccm_get_type(skb) == NFP_CCM_TYPE_BPF_BPF_EVENT) {
 		if (!nfp_bpf_event_output(bpf, skb->data, skb->len))
 			dev_consume_skb_any(skb);
 		else
 			dev_kfree_skb_any(skb);
-		return;
-	}
-
-	nfp_ctrl_lock(bpf->app->ctrl);
-
-	tag = nfp_bpf_cmsg_get_tag(skb);
-	if (unlikely(!test_bit(tag, bpf->tag_allocator))) {
-		cmsg_warn(bpf, "cmsg drop - no one is waiting for tag %u!\n",
-			  tag);
-		goto err_unlock;
 	}
 
-	__skb_queue_tail(&bpf->cmsg_replies, skb);
-	wake_up_interruptible_all(&bpf->cmsg_wq);
-
-	nfp_ctrl_unlock(bpf->app->ctrl);
-
-	return;
-err_unlock:
-	nfp_ctrl_unlock(bpf->app->ctrl);
-err_free:
-	dev_kfree_skb_any(skb);
+	nfp_ccm_rx(&bpf->ccm, skb);
 }
 
 void
 nfp_bpf_ctrl_msg_rx_raw(struct nfp_app *app, const void *data, unsigned int len)
 {
+	const struct nfp_ccm_hdr *hdr = data;
 	struct nfp_app_bpf *bpf = app->priv;
-	const struct cmsg_hdr *hdr = data;
 
 	if (unlikely(len < sizeof(struct cmsg_reply_map_simple))) {
 		cmsg_warn(bpf, "cmsg drop - too short %d!\n", len);
 		return;
 	}
 
-	if (hdr->type == CMSG_TYPE_BPF_EVENT)
+	if (hdr->type == NFP_CCM_TYPE_BPF_BPF_EVENT)
 		nfp_bpf_event_output(bpf, data, len);
 	else
 		cmsg_warn(bpf, "cmsg drop - msg type %d with raw buffer!\n",

drivers/net/ethernet/netronome/nfp/bpf/fw.h

@@ -6,6 +6,7 @@
 
 #include <linux/bitops.h>
 #include <linux/types.h>
+#include "../ccm.h"
 
 /* Kernel's enum bpf_reg_type is not uABI so people may change it breaking
  * our FW ABI.  In that case we will do translation in the driver.
@@ -52,22 +53,6 @@ struct nfp_bpf_cap_tlv_maps {
 /*
  * Types defined for map related control messages
  */
-#define CMSG_MAP_ABI_VERSION		1
-
-enum nfp_bpf_cmsg_type {
-	CMSG_TYPE_MAP_ALLOC	= 1,
-	CMSG_TYPE_MAP_FREE	= 2,
-	CMSG_TYPE_MAP_LOOKUP	= 3,
-	CMSG_TYPE_MAP_UPDATE	= 4,
-	CMSG_TYPE_MAP_DELETE	= 5,
-	CMSG_TYPE_MAP_GETNEXT	= 6,
-	CMSG_TYPE_MAP_GETFIRST	= 7,
-	CMSG_TYPE_BPF_EVENT	= 8,
-	__CMSG_TYPE_MAP_MAX,
-};
-
-#define CMSG_TYPE_MAP_REPLY_BIT		7
-#define __CMSG_REPLY(req)		(BIT(CMSG_TYPE_MAP_REPLY_BIT) | (req))
 
 /* BPF ABIv2 fixed-length control message fields */
 #define CMSG_MAP_KEY_LW			16
@@ -84,19 +69,13 @@ enum nfp_bpf_cmsg_status {
 	CMSG_RC_ERR_MAP_E2BIG		= 7,
 };
 
-struct cmsg_hdr {
-	u8 type;
-	u8 ver;
-	__be16 tag;
-};
-
 struct cmsg_reply_map_simple {
-	struct cmsg_hdr hdr;
+	struct nfp_ccm_hdr hdr;
 	__be32 rc;
 };
 
 struct cmsg_req_map_alloc_tbl {
-	struct cmsg_hdr hdr;
+	struct nfp_ccm_hdr hdr;
 	__be32 key_size;		/* in bytes */
 	__be32 value_size;		/* in bytes */
 	__be32 max_entries;
@@ -110,7 +89,7 @@ struct cmsg_reply_map_alloc_tbl {
 };
 
 struct cmsg_req_map_free_tbl {
-	struct cmsg_hdr hdr;
+	struct nfp_ccm_hdr hdr;
 	__be32 tid;
 };
 
@@ -120,7 +99,7 @@ struct cmsg_reply_map_free_tbl {
 };
 
 struct cmsg_req_map_op {
-	struct cmsg_hdr hdr;
+	struct nfp_ccm_hdr hdr;
 	__be32 tid;
 	__be32 count;
 	__be32 flags;
@@ -135,7 +114,7 @@ struct cmsg_reply_map_op {
 };
 
 struct cmsg_bpf_event {
-	struct cmsg_hdr hdr;
+	struct nfp_ccm_hdr hdr;
 	__be32 cpu_id;
 	__be64 map_ptr;
 	__be32 data_size;

drivers/net/ethernet/netronome/nfp/bpf/main.c

@@ -442,14 +442,16 @@ static int nfp_bpf_init(struct nfp_app *app)
 	bpf->app = app;
 	app->priv = bpf;
 
-	skb_queue_head_init(&bpf->cmsg_replies);
-	init_waitqueue_head(&bpf->cmsg_wq);
 	INIT_LIST_HEAD(&bpf->map_list);
 
-	err = rhashtable_init(&bpf->maps_neutral, &nfp_bpf_maps_neutral_params);
+	err = nfp_ccm_init(&bpf->ccm, app);
 	if (err)
 		goto err_free_bpf;
 
+	err = rhashtable_init(&bpf->maps_neutral, &nfp_bpf_maps_neutral_params);
+	if (err)
+		goto err_clean_ccm;
+
 	nfp_bpf_init_capabilities(bpf);
 
 	err = nfp_bpf_parse_capabilities(app);
@@ -474,6 +476,8 @@ static int nfp_bpf_init(struct nfp_app *app)
 
 err_free_neutral_maps:
 	rhashtable_destroy(&bpf->maps_neutral);
+err_clean_ccm:
+	nfp_ccm_clean(&bpf->ccm);
 err_free_bpf:
 	kfree(bpf);
 	return err;
@@ -484,7 +488,7 @@ static void nfp_bpf_clean(struct nfp_app *app)
 	struct nfp_app_bpf *bpf = app->priv;
 
 	bpf_offload_dev_destroy(bpf->bpf_dev);
-	WARN_ON(!skb_queue_empty(&bpf->cmsg_replies));
+	nfp_ccm_clean(&bpf->ccm);
 	WARN_ON(!list_empty(&bpf->map_list));
 	WARN_ON(bpf->maps_in_use || bpf->map_elems_in_use);
 	rhashtable_free_and_destroy(&bpf->maps_neutral,

drivers/net/ethernet/netronome/nfp/bpf/main.h

@@ -14,6 +14,7 @@
 #include <linux/types.h>
 #include <linux/wait.h>
 
+#include "../ccm.h"
 #include "../nfp_asm.h"
 #include "fw.h"
 
@@ -84,16 +85,10 @@ enum pkt_vec {
 /**
  * struct nfp_app_bpf - bpf app priv structure
  * @app:		backpointer to the app
+ * @ccm:		common control message handler data
  *
  * @bpf_dev:		BPF offload device handle
  *
- * @tag_allocator:	bitmap of control message tags in use
- * @tag_alloc_next:	next tag bit to allocate
- * @tag_alloc_last:	next tag bit to be freed
- *
- * @cmsg_replies:	received cmsg replies waiting to be consumed
- * @cmsg_wq:		work queue for waiting for cmsg replies
- *
  * @cmsg_key_sz:	size of key in cmsg element array
  * @cmsg_val_sz:	size of value in cmsg element array
  *
@@ -132,16 +127,10 @@ enum pkt_vec {
  */
 struct nfp_app_bpf {
 	struct nfp_app *app;
+	struct nfp_ccm ccm;
 
 	struct bpf_offload_dev *bpf_dev;
 
-	DECLARE_BITMAP(tag_allocator, U16_MAX + 1);
-	u16 tag_alloc_next;
-	u16 tag_alloc_last;
-
-	struct sk_buff_head cmsg_replies;
-	struct wait_queue_head cmsg_wq;
-
 	unsigned int cmsg_key_sz;
 	unsigned int cmsg_val_sz;
 

drivers/net/ethernet/netronome/nfp/bpf/offload.c

@@ -22,6 +22,7 @@
 #include <net/tc_act/tc_mirred.h>
 
 #include "main.h"
+#include "../ccm.h"
 #include "../nfp_app.h"
 #include "../nfp_net_ctrl.h"
 #include "../nfp_net.h"
@@ -452,7 +453,7 @@ int nfp_bpf_event_output(struct nfp_app_bpf *bpf, const void *data,
 
 	if (len < sizeof(struct cmsg_bpf_event) + pkt_size + data_size)
 		return -EINVAL;
-	if (cbe->hdr.ver != CMSG_MAP_ABI_VERSION)
+	if (cbe->hdr.ver != NFP_CCM_ABI_VERSION)
 		return -EINVAL;
 
 	rcu_read_lock();

drivers/net/ethernet/netronome/nfp/ccm.c

+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/* Copyright (C) 2016-2019 Netronome Systems, Inc. */
+
+#include <linux/bitops.h>
+
+#include "ccm.h"
+#include "nfp_app.h"
+#include "nfp_net.h"
+
+#define NFP_CCM_TYPE_REPLY_BIT		7
+#define __NFP_CCM_REPLY(req)		(BIT(NFP_CCM_TYPE_REPLY_BIT) | (req))
+
+#define ccm_warn(app, msg...)	nn_dp_warn(&(app)->ctrl->dp, msg)
+
+#define NFP_CCM_TAG_ALLOC_SPAN	(U16_MAX / 4)
+
+static bool nfp_ccm_all_tags_busy(struct nfp_ccm *ccm)
+{
+	u16 used_tags;
+
+	used_tags = ccm->tag_alloc_next - ccm->tag_alloc_last;
+
+	return used_tags > NFP_CCM_TAG_ALLOC_SPAN;
+}
+
+static int nfp_ccm_alloc_tag(struct nfp_ccm *ccm)
+{
+	/* CCM is for FW communication which is request-reply.  To make sure
+	 * we don't reuse the message ID too early after timeout - limit the
+	 * number of requests in flight.
+	 */
+	if (unlikely(nfp_ccm_all_tags_busy(ccm))) {
+		ccm_warn(ccm->app, "all FW request contexts busy!\n");
+		return -EAGAIN;
+	}
+
+	WARN_ON(__test_and_set_bit(ccm->tag_alloc_next, ccm->tag_allocator));
+	return ccm->tag_alloc_next++;
+}
+
+static void nfp_ccm_free_tag(struct nfp_ccm *ccm, u16 tag)
+{
+	WARN_ON(!__test_and_clear_bit(tag, ccm->tag_allocator));
+
+	while (!test_bit(ccm->tag_alloc_last, ccm->tag_allocator) &&
+	       ccm->tag_alloc_last != ccm->tag_alloc_next)
+		ccm->tag_alloc_last++;
+}
+
+static struct sk_buff *__nfp_ccm_reply(struct nfp_ccm *ccm, u16 tag)
+{
+	unsigned int msg_tag;
+	struct sk_buff *skb;
+
+	skb_queue_walk(&ccm->replies, skb) {
+		msg_tag = nfp_ccm_get_tag(skb);
+		if (msg_tag == tag) {
+			nfp_ccm_free_tag(ccm, tag);
+			__skb_unlink(skb, &ccm->replies);
+			return skb;
+		}
+	}
+
+	return NULL;
+}
+
+static struct sk_buff *
+nfp_ccm_reply(struct nfp_ccm *ccm, struct nfp_app *app, u16 tag)
+{
+	struct sk_buff *skb;
+
+	nfp_ctrl_lock(app->ctrl);
+	skb = __nfp_ccm_reply(ccm, tag);
+	nfp_ctrl_unlock(app->ctrl);
+
+	return skb;
+}
+
+static struct sk_buff *
+nfp_ccm_reply_drop_tag(struct nfp_ccm *ccm, struct nfp_app *app, u16 tag)
+{
+	struct sk_buff *skb;
+
+	nfp_ctrl_lock(app->ctrl);
+	skb = __nfp_ccm_reply(ccm, tag);
+	if (!skb)
+		nfp_ccm_free_tag(ccm, tag);
+	nfp_ctrl_unlock(app->ctrl);
+
+	return skb;
+}
+
+static struct sk_buff *
+nfp_ccm_wait_reply(struct nfp_ccm *ccm, struct nfp_app *app,
+		   enum nfp_ccm_type type, int tag)
+{
+	struct sk_buff *skb;
+	int i, err;
+
+	for (i = 0; i < 50; i++) {
+		udelay(4);
+		skb = nfp_ccm_reply(ccm, app, tag);
+		if (skb)
+			return skb;
+	}
+
+	err = wait_event_interruptible_timeout(ccm->wq,
+					       skb = nfp_ccm_reply(ccm, app,
+								   tag),
+					       msecs_to_jiffies(5000));
+	/* We didn't get a response - try last time and atomically drop
+	 * the tag even if no response is matched.
+	 */
+	if (!skb)
+		skb = nfp_ccm_reply_drop_tag(ccm, app, tag);
+	if (err < 0) {
+		ccm_warn(app, "%s waiting for response to 0x%02x: %d\n",
+			 err == ERESTARTSYS ? "interrupted" : "error",
+			 type, err);
+		return ERR_PTR(err);
+	}
+	if (!skb) {
+		ccm_warn(app, "timeout waiting for response to 0x%02x\n", type);
+		return ERR_PTR(-ETIMEDOUT);
+	}
+
+	return skb;
+}
+
+struct sk_buff *
+nfp_ccm_communicate(struct nfp_ccm *ccm, struct sk_buff *skb,
+		    enum nfp_ccm_type type, unsigned int reply_size)
+{
+	struct nfp_app *app = ccm->app;
+	struct nfp_ccm_hdr *hdr;
+	int reply_type, tag;
+
+	nfp_ctrl_lock(app->ctrl);
+	tag = nfp_ccm_alloc_tag(ccm);
+	if (tag < 0) {
+		nfp_ctrl_unlock(app->ctrl);
+		dev_kfree_skb_any(skb);
+		return ERR_PTR(tag);
+	}
+
+	hdr = (void *)skb->data;
+	hdr->ver = NFP_CCM_ABI_VERSION;
+	hdr->type = type;
+	hdr->tag = cpu_to_be16(tag);
+
+	__nfp_app_ctrl_tx(app, skb);
+
+	nfp_ctrl_unlock(app->ctrl);
+
+	skb = nfp_ccm_wait_reply(ccm, app, type, tag);
+	if (IS_ERR(skb))
+		return skb;
+
+	reply_type = nfp_ccm_get_type(skb);
+	if (reply_type != __NFP_CCM_REPLY(type)) {
+		ccm_warn(app, "cmsg drop - wrong type 0x%02x != 0x%02lx!\n",
+			 reply_type, __NFP_CCM_REPLY(type));
+		goto err_free;
+	}
+	/* 0 reply_size means caller will do the validation */
+	if (reply_size && skb->len != reply_size) {
+		ccm_warn(app, "cmsg drop - type 0x%02x wrong size %d != %d!\n",
+			 type, skb->len, reply_size);
+		goto err_free;
+	}
+
+	return skb;
+err_free:
+	dev_kfree_skb_any(skb);
+	return ERR_PTR(-EIO);
+}
+
+void nfp_ccm_rx(struct nfp_ccm *ccm, struct sk_buff *skb)
+{
+	struct nfp_app *app = ccm->app;
+	unsigned int tag;
+
+	if (unlikely(skb->len < sizeof(struct nfp_ccm_hdr))) {
+		ccm_warn(app, "cmsg drop - too short %d!\n", skb->len);
+		goto err_free;
+	}
+
+	nfp_ctrl_lock(app->ctrl);
+
+	tag = nfp_ccm_get_tag(skb);
+	if (unlikely(!test_bit(tag, ccm->tag_allocator))) {
+		ccm_warn(app, "cmsg drop - no one is waiting for tag %u!\n",
+			 tag);
+		goto err_unlock;
+	}
+
+	__skb_queue_tail(&ccm->replies, skb);
+	wake_up_interruptible_all(&ccm->wq);
+
+	nfp_ctrl_unlock(app->ctrl);
+	return;
+
+err_unlock:
+	nfp_ctrl_unlock(app->ctrl);
+err_free:
+	dev_kfree_skb_any(skb);
+}
+
+int nfp_ccm_init(struct nfp_ccm *ccm, struct nfp_app *app)
+{
+	ccm->app = app;
+	skb_queue_head_init(&ccm->replies);
+	init_waitqueue_head(&ccm->wq);
+	return 0;
+}
+
+void nfp_ccm_clean(struct nfp_ccm *ccm)
+{
+	WARN_ON(!skb_queue_empty(&ccm->replies));
+}

drivers/net/ethernet/netronome/nfp/ccm.h

+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+/* Copyright (C) 2016-2019 Netronome Systems, Inc. */
+
+#ifndef NFP_CCM_H
+#define NFP_CCM_H 1
+
+#include <linux/bitmap.h>
+#include <linux/skbuff.h>
+#include <linux/wait.h>
+
+struct nfp_app;
+
+/* Firmware ABI */
+
+enum nfp_ccm_type {
+	NFP_CCM_TYPE_BPF_MAP_ALLOC	= 1,
+	NFP_CCM_TYPE_BPF_MAP_FREE	= 2,
+	NFP_CCM_TYPE_BPF_MAP_LOOKUP	= 3,
+	NFP_CCM_TYPE_BPF_MAP_UPDATE	= 4,
+	NFP_CCM_TYPE_BPF_MAP_DELETE	= 5,
+	NFP_CCM_TYPE_BPF_MAP_GETNEXT	= 6,
+	NFP_CCM_TYPE_BPF_MAP_GETFIRST	= 7,
+	NFP_CCM_TYPE_BPF_BPF_EVENT	= 8,
+	__NFP_CCM_TYPE_MAX,
+};
+
+#define NFP_CCM_ABI_VERSION		1
+
+struct nfp_ccm_hdr {
+	u8 type;
+	u8 ver;
+	__be16 tag;
+};
+
+static inline u8 nfp_ccm_get_type(struct sk_buff *skb)
+{
+	struct nfp_ccm_hdr *hdr;
+
+	hdr = (struct nfp_ccm_hdr *)skb->data;
+
+	return hdr->type;
+}
+
+static inline unsigned int nfp_ccm_get_tag(struct sk_buff *skb)
+{
+	struct nfp_ccm_hdr *hdr;
+
+	hdr = (struct nfp_ccm_hdr *)skb->data;
+
+	return be16_to_cpu(hdr->tag);
+}
+
+/* Implementation */
+
+/**
+ * struct nfp_ccm - common control message handling
+ * @tag_allocator:	bitmap of control message tags in use
+ * @tag_alloc_next:	next tag bit to allocate
+ * @tag_alloc_last:	next tag bit to be freed
+ *
+ * @replies:		received cmsg replies waiting to be consumed
+ * @wq:			work queue for waiting for cmsg replies
+ */
+struct nfp_ccm {
+	struct nfp_app *app;
+
+	DECLARE_BITMAP(tag_allocator, U16_MAX + 1);
+	u16 tag_alloc_next;
+	u16 tag_alloc_last;
+
+	struct sk_buff_head replies;
+	struct wait_queue_head wq;
+};
+
+int nfp_ccm_init(struct nfp_ccm *ccm, struct nfp_app *app);
+void nfp_ccm_clean(struct nfp_ccm *ccm);
+void nfp_ccm_rx(struct nfp_ccm *ccm, struct sk_buff *skb);
+struct sk_buff *
+nfp_ccm_communicate(struct nfp_ccm *ccm, struct sk_buff *skb,
+		    enum nfp_ccm_type type, unsigned int reply_size);
+#endif