[PATCH 06/12] cxiverbs: encode list entries and VNI-isolated remote keys

[Doug Ledford]

Add cxi_le.h, which encodes receive list entries and remote keys.

A logical remote key is at most 48 bits.  The wire key is the logical
key shifted left by 16 with the job's VNI in the low 16 bits, and the
list entry clears the ignore bits covering the VNI so it is always
compared.  A logical key that does not fit is rejected with EOPNOTSUPP
rather than truncated, and a zero key is rejected with EINVAL, because
zero match bits are reserved for receives that do not use a key.

The helpers return negative errno values like the rest of the
hardware interface; the verbs entry points negate them before
setting errno.

Co-developed-by: Iraimani P <iraimani.pavadai@xxxxxxx>
Signed-off-by: Iraimani P <iraimani.pavadai@xxxxxxx>
Signed-off-by: Doug Ledford <doug.ledford@xxxxxxx>
---
 providers/cxi/cxi_le.h | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/providers/cxi/cxi_le.h b/providers/cxi/cxi_le.h
new file mode 100644
index 000000000000..096b3933adee
--- /dev/null
+++ b/providers/cxi/cxi_le.h
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
+/*
+ * Copyright 2026 Hewlett Packard Enterprise Development LP
+ */
+
+/*
+ * List entries the provider appends to an RU QP's PTE. The PTE is a
+ * matching PTE, so an entry is selected by match_bits (under ignore_bits)
+ * and by the initiator's match_id; both must be right or nothing matches.
+ */
+
+#ifndef CXI_LE_H
+#define CXI_LE_H
+
+#include <stdint.h>
+#include <errno.h>
+#include <string.h>
+#include "cxi_prov_hw.h"
+#include <rdma/cxiverbs-abi.h>
+
+/* SEND carries no key, so a receive buffer matches exactly the zero no rkey is. */
+#define CXI_LE_RECV_MATCH_BITS 0ULL
+
+#define CXI_LE_VNI_MASK 0xffffULL
+#define CXI_LE_RKEY_MAX 0xffffffffffffULL
+
+static inline int cxi_le_wire_key(uint64_t rkey, uint64_t *wire_key)
+{
+	if (rkey > CXI_LE_RKEY_MAX)
+		return -EOPNOTSUPP;
+	*wire_key = rkey << 16;
+	return 0;
+}
+
+static inline int cxi_le_set_vni(union c_cmdu *cmd, uint64_t rkey, uint16_t vni)
+{
+	uint64_t wire_key;
+	int ret = cxi_le_wire_key(rkey, &wire_key);
+
+	if (ret)
+		return ret;
+	cmd->target.match_bits = wire_key | vni;
+	cmd->target.ignore_bits &= ~CXI_LE_VNI_MASK;
+	return 0;
+}
+
+static inline void cxi_le_recv(union c_cmdu *cmd, uint16_t ptlte_index, uint8_t lac, uint64_t iova,
+			       uint64_t length)
+{
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->command.opcode = C_CMD_TGT_APPEND;
+	cmd->target.ptlte_index = ptlte_index;
+	cmd->target.ptl_list = C_PTL_LIST_PRIORITY;
+	cmd->target.op_put = 1;
+	cmd->target.use_once = 1;
+	cmd->target.lac = lac;
+	cmd->target.start = iova;
+	cmd->target.length = length;
+	cmd->target.match_bits = CXI_LE_RECV_MATCH_BITS;
+	cmd->target.ignore_bits = 0;
+	cmd->target.match_id = CXI_MATCH_ID_ANY;
+}
+
+/*
+ * An attached region matches its rkey exactly: a region reachable by a
+ * narrow key is made that way at registration, so the key carries its own
+ * width. It persists until detached, and buffer_id names it for the unlink.
+ */
+static inline void cxi_le_region(union c_cmdu *cmd, uint16_t ptlte_index, uint64_t lkey64,
+				 uint64_t rkey64, uint64_t iova, uint64_t length)
+{
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->command.opcode = C_CMD_TGT_APPEND;
+	cmd->target.ptlte_index = ptlte_index;
+	cmd->target.ptl_list = C_PTL_LIST_PRIORITY;
+	cmd->target.op_put = 1;
+	cmd->target.op_get = 1;
+	cmd->target.lac = lkey64 & CXI_LKEY64_LAC_MASK;
+	cmd->target.start = iova;
+	cmd->target.length = length;
+	cmd->target.match_bits = rkey64;
+	cmd->target.ignore_bits = 0;
+	cmd->target.match_id = CXI_MATCH_ID_ANY;
+	cmd->target.use_once = 0;
+	cmd->target.buffer_id = (uint16_t)(rkey64 & 0xffff);
+}
+
+static inline void cxi_le_region_unlink(union c_cmdu *cmd, uint16_t ptlte_index, uint64_t rkey64)
+{
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->command.opcode = C_CMD_TGT_UNLINK;
+	cmd->target.ptlte_index = ptlte_index;
+	cmd->target.ptl_list = C_PTL_LIST_PRIORITY;
+	cmd->target.buffer_id = (uint16_t)(rkey64 & 0xffff);
+}
+
+#endif /* CXI_LE_H */

-- 
2.56.0