nfp: bpf: add basic control channel communication

For map support we will need to send and receive control messages.
Add basic support for sending a message to FW, and waiting for a
reply.

Control messages are tagged with a 16 bit ID.  Add a simple ID
allocator and make sure we don't allow too many messages in flight,
to avoid request <> reply mismatches.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/netronome/nfp/Makefile

@@ -44,6 +44,7 @@ endif
 
 ifeq ($(CONFIG_BPF_SYSCALL),y)
 nfp-objs += \
+	    bpf/cmsg.o \
 	    bpf/main.o \
 	    bpf/offload.o \
 	    bpf/verifier.o \

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

@@ -0,0 +1,238 @@
+/*
+ * Copyright (C) 2017 Netronome Systems, Inc.
+ *
+ * This software is dual licensed under the GNU General License Version 2,
+ * June 1991 as shown in the file COPYING in the top-level directory of this
+ * source tree or the BSD 2-Clause License provided below.  You have the
+ * option to license this software under the complete terms of either license.
+ *
+ * The BSD 2-Clause License:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      1. Redistributions of source code must retain the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer.
+ *
+ *      2. Redistributions in binary form must reproduce the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer in the documentation and/or other materials
+ *         provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/bitops.h>
+#include <linux/bug.h>
+#include <linux/jiffies.h>
+#include <linux/skbuff.h>
+#include <linux/wait.h>
+
+#include "../nfp_app.h"
+#include "../nfp_net.h"
+#include "fw.h"
+#include "main.h"
+
+#define cmsg_warn(bpf, msg...)	nn_dp_warn(&(bpf)->app->ctrl->dp, msg)
+
+#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 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 err;
+
+	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;
+}
+
+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;
+	/* 0 reply_size means caller will do the validation */
+	if (reply_size && skb->len != reply_size) {
+		cmsg_warn(bpf, "cmsg drop - wrong size %d != %d!\n",
+			  skb->len, reply_size);
+		goto err_free;
+	}
+	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;
+	}
+
+	return skb;
+err_free:
+	dev_kfree_skb_any(skb);
+	return ERR_PTR(-EIO);
+}
+
+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;
+	}
+
+	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);
+}

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

@@ -51,4 +51,26 @@ struct nfp_bpf_cap_tlv_adjust_head {
 
 #define NFP_BPF_ADJUST_HEAD_NO_META	BIT(0)
 
+/*
+ * Types defined for map related control messages
+ */
+#define CMSG_MAP_ABI_VERSION		1
+
+enum nfp_bpf_cmsg_type {
+	__CMSG_TYPE_MAP_MAX,
+};
+
+#define CMSG_TYPE_MAP_REPLY_BIT		7
+#define __CMSG_REPLY(req)		(BIT(CMSG_TYPE_MAP_REPLY_BIT) | (req))
+
+struct cmsg_hdr {
+	u8 type;
+	u8 ver;
+	__be16 tag;
+};
+
+struct cmsg_reply_map_simple {
+	struct cmsg_hdr hdr;
+	__be32 rc;
+};
 #endif

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

@@ -313,6 +313,8 @@ 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 = nfp_bpf_parse_capabilities(app);
@@ -330,6 +332,7 @@ static void nfp_bpf_clean(struct nfp_app *app)
 {
 	struct nfp_app_bpf *bpf = app->priv;
 
+	WARN_ON(!skb_queue_empty(&bpf->cmsg_replies));
 	WARN_ON(!list_empty(&bpf->map_list));
 	kfree(bpf);
 }
@@ -348,6 +351,8 @@ const struct nfp_app_type app_bpf = {
 	.vnic_alloc	= nfp_bpf_vnic_alloc,
 	.vnic_free	= nfp_bpf_vnic_free,
 
+	.ctrl_msg_rx	= nfp_bpf_ctrl_msg_rx,
+
 	.setup_tc	= nfp_bpf_setup_tc,
 	.tc_busy	= nfp_bpf_tc_busy,
 	.bpf		= nfp_ndo_bpf,

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

@@ -37,10 +37,14 @@
 #include <linux/bitfield.h>
 #include <linux/bpf.h>
 #include <linux/bpf_verifier.h>
+#include <linux/kernel.h>
 #include <linux/list.h>
+#include <linux/skbuff.h>
 #include <linux/types.h>
+#include <linux/wait.h>
 
 #include "../nfp_asm.h"
+#include "fw.h"
 
 /* For relocation logic use up-most byte of branch instruction as scratch
  * area.  Remember to clear this before sending instructions to HW!
@@ -93,6 +97,13 @@ enum pkt_vec {
  * struct nfp_app_bpf - bpf app priv structure
  * @app:		backpointer to the app
  *
+ * @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
+ *
  * @map_list:		list of offloaded maps
  *
  * @adjust_head:	adjust head capability
@@ -105,6 +116,13 @@ enum pkt_vec {
 struct nfp_app_bpf {
 	struct nfp_app *app;
 
+	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;
+
 	struct list_head map_list;
 
 	struct nfp_bpf_cap_adjust_head {
@@ -284,4 +302,9 @@ nfp_bpf_goto_meta(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 		  unsigned int insn_idx, unsigned int n_insns);
 
 void *nfp_bpf_relo_for_vnic(struct nfp_prog *nfp_prog, struct nfp_bpf_vnic *bv);
+
+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);
+void nfp_bpf_ctrl_msg_rx(struct nfp_app *app, struct sk_buff *skb);
 #endif

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

@@ -165,6 +165,7 @@ struct nfp_app {
 	void *priv;
 };
 
+bool __nfp_ctrl_tx(struct nfp_net *nn, struct sk_buff *skb);
 bool nfp_ctrl_tx(struct nfp_net *nn, struct sk_buff *skb);
 
 static inline int nfp_app_init(struct nfp_app *app)
@@ -326,6 +327,14 @@ static inline int nfp_app_xdp_offload(struct nfp_app *app, struct nfp_net *nn,
 	return app->type->xdp_offload(app, nn, prog);
 }
 
+static inline bool __nfp_app_ctrl_tx(struct nfp_app *app, struct sk_buff *skb)
+{
+	trace_devlink_hwmsg(priv_to_devlink(app->pf), false, 0,
+			    skb->data, skb->len);
+
+	return __nfp_ctrl_tx(app->ctrl, skb);
+}
+
 static inline bool nfp_app_ctrl_tx(struct nfp_app *app, struct sk_buff *skb)
 {
 	trace_devlink_hwmsg(priv_to_devlink(app->pf), false, 0,

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

@@ -839,6 +839,18 @@ static inline const char *nfp_net_name(struct nfp_net *nn)
 	return nn->dp.netdev ? nn->dp.netdev->name : "ctrl";
 }
 
+static inline void nfp_ctrl_lock(struct nfp_net *nn)
+	__acquires(&nn->r_vecs[0].lock)
+{
+	spin_lock_bh(&nn->r_vecs[0].lock);
+}
+
+static inline void nfp_ctrl_unlock(struct nfp_net *nn)
+	__releases(&nn->r_vecs[0].lock)
+{
+	spin_unlock_bh(&nn->r_vecs[0].lock);
+}
+
 /* Globals */
 extern const char nfp_driver_version[];