enic: add MBOX VF handlers for capability, register and link state

Implement VF-side mailbox message processing for SR-IOV V2
admin channel communication.

VF receive handlers:
  - VF_CAPABILITY_REPLY: store PF protocol version, signal
    completion
  - VF_REGISTER_REPLY: mark VF as registered, signal completion
  - VF_UNREGISTER_REPLY: mark VF as unregistered, signal
    completion
  - PF_LINK_STATE_NOTIF: update carrier state via
    netif_carrier_on/off, send ACK back to PF

VF initiation functions for the probe-time handshake:
  - enic_mbox_vf_capability_check: send capability request,
    wait for PF reply via completion
  - enic_mbox_vf_register: send register request, wait for
    PF confirmation via completion
  - enic_mbox_vf_unregister: send unregister request, wait
    for PF confirmation

The wait helper (enic_mbox_wait_reply) uses
wait_for_completion_timeout, signaled when the admin ISR and
CQ-poll/dispatch workqueue pipeline delivers the reply message.

mbox_expected_reply is written by the request thread and read by the
admin CQ poll/dispatch context that runs the receive handlers; annotate
those accesses with READ_ONCE()/WRITE_ONCE() under the
single-outstanding-reply invariant.

Signed-off-by: Satish Kharat <satishkh@cisco.com>
Link: https://patch.msgid.link/20260812-enic-sriov-v2-admin-channel-v2-v13-8-b3809e448aba@cisco.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/cisco/enic/enic.h

@@ -258,6 +258,8 @@ struct enic {
 	u32 tx_coalesce_usecs;
 	u16 num_vfs;
 	enum enic_vf_type vf_type;
+	bool vf_registered;
+	u32 pf_cap_version;
 	unsigned int enable_count;
 	spinlock_t enic_api_lock;
 	bool enic_api_busy;
@@ -313,6 +315,16 @@ struct enic {
 	/* MBOX protocol state — mbox_lock serializes admin WQ sends */
 	struct mutex mbox_lock;
 	u64 mbox_msg_num;
+	/* MBOX request-reply state.  mbox_expected_reply is written and
+	 * cleared by the process-context request helpers (capability/register/
+	 * unregister) and only read by the admin_msg_work receive handlers, so
+	 * it is annotated with READ_ONCE()/WRITE_ONCE() rather than locked:
+	 * only one request is in flight at a time (requesters run under RTNL or
+	 * single-threaded probe/remove), so each request is serialized and its
+	 * reply completes mbox_comp before the next request is issued.
+	 */
+	struct completion mbox_comp;
+	u8 mbox_expected_reply;
 
 	/* PF: per-VF MBOX state, allocated when SRIOV V2 is enabled */
 	struct enic_vf_state {

drivers/net/ethernet/cisco/enic/enic_mbox.c

@@ -5,6 +5,7 @@
 #include <linux/netdevice.h>
 #include <linux/dma-mapping.h>
 #include <linux/delay.h>
+#include <linux/completion.h>
 
 #include "vnic_dev.h"
 #include "vnic_wq.h"
@@ -142,6 +143,16 @@ int enic_mbox_send_msg(struct enic *enic, u8 msg_type, u16 dst_vnic_id,
 	return err;
 }
 
+static int enic_mbox_wait_reply(struct enic *enic, unsigned long timeout_ms)
+{
+	unsigned long left;
+
+	left = wait_for_completion_timeout(&enic->mbox_comp,
+					   msecs_to_jiffies(timeout_ms));
+
+	return left ? 0 : -ETIMEDOUT;
+}
+
 int enic_mbox_send_link_state(struct enic *enic, u16 vf_id, u32 link_state)
 {
 	struct enic_mbox_pf_link_state_notif_msg notif = {};
@@ -313,6 +324,166 @@ static void enic_mbox_pf_process_msg(struct enic *enic,
 			    hdr->msg_type, vf_id, err);
 }
 
+static void enic_mbox_vf_handle_capability_reply(struct enic *enic,
+						 void *payload)
+{
+	struct enic_mbox_vf_capability_reply_msg *reply = payload;
+
+	if (READ_ONCE(enic->mbox_expected_reply) != ENIC_MBOX_VF_CAPABILITY_REPLY) {
+		netdev_warn(enic->netdev,
+			    "MBOX: stale capability reply (expected %u), drop\n",
+			    READ_ONCE(enic->mbox_expected_reply));
+		return;
+	}
+
+	if (le16_to_cpu(reply->reply.ret_major) == 0)
+		enic->pf_cap_version = le32_to_cpu(reply->version);
+	else
+		netdev_warn(enic->netdev,
+			    "MBOX: PF rejected capability request: %u/%u\n",
+			    le16_to_cpu(reply->reply.ret_major),
+			    le16_to_cpu(reply->reply.ret_minor));
+	complete(&enic->mbox_comp);
+}
+
+static void enic_mbox_vf_handle_register_reply(struct enic *enic,
+					       void *payload)
+{
+	struct enic_mbox_vf_register_reply_msg *reply = payload;
+
+	if (READ_ONCE(enic->mbox_expected_reply) != ENIC_MBOX_VF_REGISTER_REPLY) {
+		netdev_warn(enic->netdev,
+			    "MBOX: stale register reply (expected %u), drop\n",
+			    READ_ONCE(enic->mbox_expected_reply));
+		return;
+	}
+
+	if (le16_to_cpu(reply->reply.ret_major)) {
+		netdev_warn(enic->netdev,
+			    "MBOX: VF register rejected by PF: %u/%u\n",
+			    le16_to_cpu(reply->reply.ret_major),
+			    le16_to_cpu(reply->reply.ret_minor));
+	} else {
+		enic->vf_registered = true;
+	}
+	complete(&enic->mbox_comp);
+}
+
+static void enic_mbox_vf_handle_unregister_reply(struct enic *enic,
+						 void *payload)
+{
+	struct enic_mbox_vf_register_reply_msg *reply = payload;
+
+	if (READ_ONCE(enic->mbox_expected_reply) != ENIC_MBOX_VF_UNREGISTER_REPLY) {
+		netdev_warn(enic->netdev,
+			    "MBOX: stale unregister reply (expected %u), drop\n",
+			    READ_ONCE(enic->mbox_expected_reply));
+		return;
+	}
+
+	if (le16_to_cpu(reply->reply.ret_major)) {
+		netdev_warn(enic->netdev,
+			    "MBOX: VF unregister rejected by PF: %u/%u\n",
+			    le16_to_cpu(reply->reply.ret_major),
+			    le16_to_cpu(reply->reply.ret_minor));
+	} else {
+		enic->vf_registered = false;
+	}
+	complete(&enic->mbox_comp);
+}
+
+static void enic_mbox_vf_handle_link_state(struct enic *enic, void *payload)
+{
+	struct enic_mbox_pf_link_state_notif_msg *notif = payload;
+	struct enic_mbox_pf_link_state_ack_msg ack = {};
+	int err;
+
+	switch (le32_to_cpu(notif->link_state)) {
+	case ENIC_MBOX_LINK_STATE_ENABLE:
+		if (!netif_carrier_ok(enic->netdev))
+			netif_carrier_on(enic->netdev);
+		netdev_dbg(enic->netdev, "MBOX: link state -> UP\n");
+		break;
+	case ENIC_MBOX_LINK_STATE_DISABLE:
+		if (netif_carrier_ok(enic->netdev))
+			netif_carrier_off(enic->netdev);
+		netdev_dbg(enic->netdev, "MBOX: link state -> DOWN\n");
+		break;
+	default:
+		netdev_warn(enic->netdev, "MBOX: unknown link state %u\n",
+			    le32_to_cpu(notif->link_state));
+		ack.ack.ret_major = cpu_to_le16(ENIC_MBOX_ERR_GENERIC);
+		break;
+	}
+
+	err = enic_mbox_send_msg(enic, ENIC_MBOX_PF_LINK_STATE_ACK,
+				 ENIC_MBOX_DST_PF, &ack, sizeof(ack));
+	if (err && net_ratelimit())
+		netdev_warn(enic->netdev,
+			    "MBOX: failed to send link state ACK: %d\n", err);
+}
+
+static bool enic_mbox_vf_payload_ok(struct enic *enic, u8 msg_type,
+				    u16 payload_len, size_t min_len)
+{
+	if (payload_len < min_len) {
+		netdev_warn(enic->netdev,
+			    "MBOX: short payload for type %u (%u < %zu)\n",
+			    msg_type, payload_len, min_len);
+		return false;
+	}
+	return true;
+}
+
+static void enic_mbox_vf_process_msg(struct enic *enic,
+				     struct enic_mbox_hdr *hdr, void *payload,
+				     u16 payload_len)
+{
+	switch (hdr->msg_type) {
+	case ENIC_MBOX_VF_CAPABILITY_REPLY: {
+		size_t exp = sizeof(struct enic_mbox_vf_capability_reply_msg);
+
+		if (!enic_mbox_vf_payload_ok(enic, hdr->msg_type,
+					     payload_len, exp))
+			return;
+		enic_mbox_vf_handle_capability_reply(enic, payload);
+		break;
+	}
+	case ENIC_MBOX_VF_REGISTER_REPLY: {
+		size_t exp = sizeof(struct enic_mbox_vf_register_reply_msg);
+
+		if (!enic_mbox_vf_payload_ok(enic, hdr->msg_type,
+					     payload_len, exp))
+			return;
+		enic_mbox_vf_handle_register_reply(enic, payload);
+		break;
+	}
+	case ENIC_MBOX_VF_UNREGISTER_REPLY: {
+		size_t exp = sizeof(struct enic_mbox_vf_register_reply_msg);
+
+		if (!enic_mbox_vf_payload_ok(enic, hdr->msg_type,
+					     payload_len, exp))
+			return;
+		enic_mbox_vf_handle_unregister_reply(enic, payload);
+		break;
+	}
+	case ENIC_MBOX_PF_LINK_STATE_NOTIF: {
+		size_t exp = sizeof(struct enic_mbox_pf_link_state_notif_msg);
+
+		if (!enic_mbox_vf_payload_ok(enic, hdr->msg_type,
+					     payload_len, exp))
+			return;
+		enic_mbox_vf_handle_link_state(enic, payload);
+		break;
+	}
+	default:
+		netdev_dbg(enic->netdev,
+			   "MBOX: VF unhandled msg type %u\n",
+			   hdr->msg_type);
+		break;
+	}
+}
+
 static void enic_mbox_recv_handler(struct enic *enic, void *buf,
 				   unsigned int len)
 {
@@ -351,13 +522,117 @@ static void enic_mbox_recv_handler(struct enic *enic, void *buf,
 
 	payload = buf + sizeof(*hdr);
 
-	if (enic->vf_state)
+	if (enic->vf_state) {
 		enic_mbox_pf_process_msg(enic, hdr, payload);
+	} else if (le16_to_cpu(hdr->src_vnic_id) == ENIC_MBOX_DST_PF) {
+		/* src_vnic_id was overwritten from the hardware-verified CQ
+		 * VLAN sender field, so a VF only accepts messages that the
+		 * adapter attributes to the PF.  Its sole admin-channel peer is
+		 * the PF; drop anything else as a spoofed notification.
+		 */
+		enic_mbox_vf_process_msg(enic, hdr, payload,
+					 msg_len - (u16)sizeof(*hdr));
+	} else if (net_ratelimit()) {
+		netdev_warn(enic->netdev,
+			    "MBOX: VF dropping non-PF message from vnic %u\n",
+			    le16_to_cpu(hdr->src_vnic_id));
+	}
+}
+
+int enic_mbox_vf_capability_check(struct enic *enic)
+{
+	struct enic_mbox_vf_capability_msg req = {};
+	int err;
+
+	enic->pf_cap_version = 0;
+	reinit_completion(&enic->mbox_comp);
+	WRITE_ONCE(enic->mbox_expected_reply, ENIC_MBOX_VF_CAPABILITY_REPLY);
+	req.version = cpu_to_le32(ENIC_MBOX_CAP_VERSION_1);
+
+	err = enic_mbox_send_msg(enic, ENIC_MBOX_VF_CAPABILITY_REQUEST,
+				 ENIC_MBOX_DST_PF, &req, sizeof(req));
+	if (err) {
+		WRITE_ONCE(enic->mbox_expected_reply, 0);
+		return err;
+	}
+
+	err = enic_mbox_wait_reply(enic, 3000);
+	WRITE_ONCE(enic->mbox_expected_reply, 0);
+	if (err) {
+		netdev_warn(enic->netdev,
+			    "MBOX: no capability reply from PF\n");
+		return err;
+	}
+
+	if (enic->pf_cap_version < ENIC_MBOX_CAP_VERSION_1) {
+		netdev_warn(enic->netdev,
+			    "MBOX: PF rejected capability request or reported unsupported version %u\n",
+			    enic->pf_cap_version);
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+int enic_mbox_vf_register(struct enic *enic)
+{
+	int err;
+
+	enic->vf_registered = false;
+	reinit_completion(&enic->mbox_comp);
+	WRITE_ONCE(enic->mbox_expected_reply, ENIC_MBOX_VF_REGISTER_REPLY);
+
+	err = enic_mbox_send_msg(enic, ENIC_MBOX_VF_REGISTER_REQUEST,
+				 ENIC_MBOX_DST_PF, NULL, 0);
+	if (err) {
+		WRITE_ONCE(enic->mbox_expected_reply, 0);
+		return err;
+	}
+
+	err = enic_mbox_wait_reply(enic, 3000);
+	WRITE_ONCE(enic->mbox_expected_reply, 0);
+	if (err) {
+		netdev_warn(enic->netdev,
+			    "MBOX: VF registration with PF timed out\n");
+		return err;
+	}
+
+	if (!enic->vf_registered)
+		return -ENODEV;
+
+	return 0;
+}
+
+int enic_mbox_vf_unregister(struct enic *enic)
+{
+	int err;
+
+	if (!enic->vf_registered)
+		return 0;
+
+	reinit_completion(&enic->mbox_comp);
+	WRITE_ONCE(enic->mbox_expected_reply, ENIC_MBOX_VF_UNREGISTER_REPLY);
+
+	err = enic_mbox_send_msg(enic, ENIC_MBOX_VF_UNREGISTER_REQUEST,
+				 ENIC_MBOX_DST_PF, NULL, 0);
+	if (err) {
+		WRITE_ONCE(enic->mbox_expected_reply, 0);
+		return err;
+	}
+
+	err = enic_mbox_wait_reply(enic, 3000);
+	WRITE_ONCE(enic->mbox_expected_reply, 0);
+	if (err)
+		return err;
+	if (enic->vf_registered)
+		return -EACCES;
+	return 0;
 }
 
 void enic_mbox_init(struct enic *enic)
 {
 	enic->mbox_msg_num = 0;
 	mutex_init(&enic->mbox_lock);
+	init_completion(&enic->mbox_comp);
 	enic->admin_rq_handler = enic_mbox_recv_handler;
 }

drivers/net/ethernet/cisco/enic/enic_mbox.h

@@ -88,5 +88,8 @@ void enic_mbox_init(struct enic *enic);
 int enic_mbox_send_msg(struct enic *enic, u8 msg_type, u16 dst_vnic_id,
 		       void *payload, u16 payload_len);
 int enic_mbox_send_link_state(struct enic *enic, u16 vf_id, u32 link_state);
+int enic_mbox_vf_capability_check(struct enic *enic);
+int enic_mbox_vf_register(struct enic *enic);
+int enic_mbox_vf_unregister(struct enic *enic);
 
 #endif /* _ENIC_MBOX_H_ */