It'll be annoying and take enough of boilerplate code to implement
new zcrx features as separate io_uring register opcode. Introduce
IORING_REGISTER_ZCRX_CTRL that will multiplex such calls to zcrx.
Note, there are no real users of the opcode in this patch.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring.h | 13 +++++++++++++
 io_uring/register.c           |  3 +++
 io_uring/zcrx.c               | 21 +++++++++++++++++++++
 io_uring/zcrx.h               |  6 ++++++
 4 files changed, 43 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 3d921cbb84f8..5b7851704efe 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -701,6 +701,9 @@ enum io_uring_register_op {
 	/* query various aspects of io_uring, see linux/io_uring/query.h */
 	IORING_REGISTER_QUERY			= 35,
 
+	/* auxiliary zcrx configuration, see enum zcrx_ctrl_op */
+	IORING_REGISTER_ZCRX_CTRL		= 36,
+
 	/* this goes last */
 	IORING_REGISTER_LAST,
 
@@ -1082,6 +1085,16 @@ struct io_uring_zcrx_ifq_reg {
 	__u64	__resv[3];
 };
 
+enum zcrx_ctrl_op {
+	__ZCRX_CTRL_LAST,
+};
+
+struct zcrx_ctrl {
+	__u32	zcrx_id;
+	__u32	op; /* see enum zcrx_ctrl_op */
+	__u64	__resv[8];
+};
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/io_uring/register.c b/io_uring/register.c
index ec13ff876a38..2761a751ab66 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -826,6 +826,9 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 	case IORING_REGISTER_QUERY:
 		ret = io_query(ctx, arg, nr_args);
 		break;
+	case IORING_REGISTER_ZCRX_CTRL:
+		ret = io_zcrx_ctrl(ctx, arg, nr_args);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 149bf9d5b983..0b5f4320c7a9 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -941,6 +941,27 @@ static const struct memory_provider_ops io_uring_pp_zc_ops = {
 	.uninstall		= io_pp_uninstall,
 };
 
+int io_zcrx_ctrl(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
+{
+	struct zcrx_ctrl ctrl;
+	struct io_zcrx_ifq *zcrx;
+
+	if (nr_args)
+		return -EINVAL;
+	if (copy_from_user(&ctrl, arg, sizeof(ctrl)))
+		return -EFAULT;
+	if (!mem_is_zero(&ctrl.__resv, sizeof(ctrl.__resv)))
+		return -EFAULT;
+
+	zcrx = xa_load(&ctx->zcrx_ctxs, ctrl.zcrx_id);
+	if (!zcrx)
+		return -ENXIO;
+	if (ctrl.op >= __ZCRX_CTRL_LAST)
+		return -EOPNOTSUPP;
+
+	return -EINVAL;
+}
+
 static bool io_zcrx_queue_cqe(struct io_kiocb *req, struct net_iov *niov,
 			      struct io_zcrx_ifq *ifq, int off, int len)
 {
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index c9b9bfae0547..f29edc22c91f 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -65,6 +65,7 @@ struct io_zcrx_ifq {
 };
 
 #if defined(CONFIG_IO_URING_ZCRX)
+int io_zcrx_ctrl(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_arg);
 int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 			 struct io_uring_zcrx_ifq_reg __user *arg);
 void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx);
@@ -93,6 +94,11 @@ static inline struct io_mapped_region *io_zcrx_get_region(struct io_ring_ctx *ct
 {
 	return NULL;
 }
+static inline int io_zcrx_ctrl(struct io_ring_ctx *ctx,
+				void __user *arg, unsigned nr_arg)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 int io_recvzc(struct io_kiocb *req, unsigned int issue_flags);
-- 
2.49.0