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>

1 files changed, 238 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c b/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
new file mode 100644
index 000000000000..46753ee9f7c5
--- /dev/null
+++ b/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);
+}