[PATCH net-next 06/14] net/dibs: Define dibs loopback

Alexandra Winter
2025-09-05T14:54:46Z

The first stage of loopback-ism was implemented as part of the
SMC module [1]. Now that we have the dibs layer, provide access to a
dibs_loopback device to all dibs clients.

This is the first step of moving loopback-ism from net/smc/smc_loopback.*
to net/dibs/dibs_loopback.*. One global structure lo_dev is allocated
and added to the dibs devices. Follow-on patches will move functionality.

Same as smc_loopback, dibs_loopback is provided by a config option.
Note that there is no way to dynamically add or remove the loopback
device. That could be a future improvement.

When moving code to net/dibs, replace ism_ prefix with dibs_ prefix.
As this is mostly a move of existing code, copyright and authors are
unchanged.

Link: https://lore.kernel.org/lkml/20240428060738.60843-1-guwen@linux.alibaba.com/ [1]

Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
---
arch/s390/configs/debug_defconfig | 1 +
arch/s390/configs/defconfig | 1 +
net/dibs/Kconfig | 11 +++++
net/dibs/Makefile | 1 +
net/dibs/dibs_loopback.c | 78 +++++++++++++++++++++++++++++++
net/dibs/dibs_loopback.h | 38 +++++++++++++++
net/dibs/dibs_main.c | 11 ++++-
7 files changed, 140 insertions(+), 1 deletion(-)
create mode 100644 net/dibs/dibs_loopback.c
create mode 100644 net/dibs/dibs_loopback.h

diff --git a/arch/s390/configs/debug_defconfig b/arch/s390/configs/debug_defconfig
index 7bc54f053a3b..5a2ed07b6198 100644
--- a/arch/s390/configs/debug_defconfig
+++ b/arch/s390/configs/debug_defconfig
@@ -121,6 +121,7 @@ CONFIG_UNIX_DIAG=m
CONFIG_XFRM_USER=m
CONFIG_NET_KEY=m
CONFIG_DIBS=y
+CONFIG_DIBS_LO=y
CONFIG_SMC_DIAG=m
CONFIG_SMC_LO=y
CONFIG_INET=y
diff --git a/arch/s390/configs/defconfig b/arch/s390/configs/defconfig
index 4bf6f3311f7d..4cbdd7e2ff9f 100644
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -112,6 +112,7 @@ CONFIG_UNIX_DIAG=m
CONFIG_XFRM_USER=m
CONFIG_NET_KEY=m
CONFIG_DIBS=y
+CONFIG_DIBS_LO=y
CONFIG_SMC_DIAG=m
CONFIG_SMC_LO=y
CONFIG_INET=y
diff --git a/net/dibs/Kconfig b/net/dibs/Kconfig
index 09c12f6838ad..5dc347b9b235 100644
--- a/net/dibs/Kconfig
+++ b/net/dibs/Kconfig
@@ -10,3 +10,14 @@ config DIBS
Select this option to provide the abstraction layer between
dibs devices and dibs clients like the SMC protocol.
The module name is dibs.
+
+config DIBS_LO
+ bool "intra-OS shortcut with dibs loopback"
+ depends on DIBS
+ default n
+ help
+ DIBS_LO enables the creation of an software-emulated dibs device
+ named lo which can be used for transferring data when communication
+ occurs within the same OS. This helps in convenient testing of
+ dibs clients, since dibs loopback is independent of architecture or
+ hardware.
diff --git a/net/dibs/Makefile b/net/dibs/Makefile
index 825dec431bfc..85805490c77f 100644
--- a/net/dibs/Makefile
+++ b/net/dibs/Makefile
@@ -5,3 +5,4 @@

dibs-y += dibs_main.o
obj-$(CONFIG_DIBS) += dibs.o
+dibs-$(CONFIG_DIBS_LO) += dibs_loopback.o
\ No newline at end of file
diff --git a/net/dibs/dibs_loopback.c b/net/dibs/dibs_loopback.c
new file mode 100644
index 000000000000..225514a452a8
--- /dev/null
+++ b/net/dibs/dibs_loopback.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions for dibs loopback/loopback-ism device.
+ *
+ * Copyright (c) 2024, Alibaba Inc.
+ *
+ * Author: Wen Gu <guwen@linux.alibaba.com>
+ * Tony Lu <tonylu@linux.alibaba.com>
+ *
+ */
+
+#include <linux/dibs.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "dibs_loopback.h"
+
+/* global loopback device */
+static struct dibs_lo_dev *lo_dev;
+
+static void dibs_lo_dev_exit(struct dibs_lo_dev *ldev)
+{
+ dibs_dev_del(ldev->dibs);
+}
+
+static int dibs_lo_dev_probe(void)
+{
+ struct dibs_lo_dev *ldev;
+ struct dibs_dev *dibs;
+ int ret;
+
+ ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
+ if (!ldev)
+ return -ENOMEM;
+
+ dibs = dibs_dev_alloc();
+ if (!dibs) {
+ kfree(ldev);
+ return -ENOMEM;
+ }
+
+ ldev->dibs = dibs;
+
+ ret = dibs_dev_add(dibs);
+ if (ret)
+ goto err_reg;
+ lo_dev = ldev;
+ return 0;
+
+err_reg:
+ /* pairs with dibs_dev_alloc() */
+ kfree(dibs);
+ kfree(ldev);
+
+ return ret;
+}
+
+static void dibs_lo_dev_remove(void)
+{
+ if (!lo_dev)
+ return;
+
+ dibs_lo_dev_exit(lo_dev);
+ /* pairs with dibs_dev_alloc() */
+ kfree(lo_dev->dibs);
+ kfree(lo_dev);
+ lo_dev = NULL;
+}
+
+int dibs_loopback_init(void)
+{
+ return dibs_lo_dev_probe();
+}
+
+void dibs_loopback_exit(void)
+{
+ dibs_lo_dev_remove();
+}
diff --git a/net/dibs/dibs_loopback.h b/net/dibs/dibs_loopback.h
new file mode 100644
index 000000000000..fd03b6333a24
--- /dev/null
+++ b/net/dibs/dibs_loopback.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * dibs loopback (aka loopback-ism) device structure definitions.
+ *
+ * Copyright (c) 2024, Alibaba Inc.
+ *
+ * Author: Wen Gu <guwen@linux.alibaba.com>
+ * Tony Lu <tonylu@linux.alibaba.com>
+ *
+ */
+
+#ifndef _DIBS_LOOPBACK_H
+#define _DIBS_LOOPBACK_H
+
+#include <linux/dibs.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+
+#if IS_ENABLED(CONFIG_DIBS_LO)
+
+struct dibs_lo_dev {
+ struct dibs_dev *dibs;
+};
+
+int dibs_loopback_init(void);
+void dibs_loopback_exit(void);
+#else
+static inline int dibs_loopback_init(void)
+{
+ return 0;
+}
+
+static inline void dibs_loopback_exit(void)
+{
+}
+#endif
+
+#endif /* _DIBS_LOOPBACK_H */
diff --git a/net/dibs/dibs_main.c b/net/dibs/dibs_main.c
index 2f420e077417..a7e33be36158 100644
--- a/net/dibs/dibs_main.c
+++ b/net/dibs/dibs_main.c
@@ -15,6 +15,8 @@
#include <linux/err.h>
#include <linux/dibs.h>

+#include "dibs_loopback.h"
+
MODULE_DESCRIPTION("Direct Internal Buffer Sharing class");
MODULE_LICENSE("GPL");

@@ -96,14 +98,21 @@ EXPORT_SYMBOL_GPL(dibs_dev_del);

static int __init dibs_init(void)
{
+ int rc;
+
memset(clients, 0, sizeof(clients));
max_client = 0;

- return 0;
+ rc = dibs_loopback_init();
+ if (rc)
+ pr_err("%s fails with %d\n", __func__, rc);
+
+ return rc;
}

static void __exit dibs_exit(void)
{
+ dibs_loopback_exit();
}

module_init(dibs_init);
--
2.48.1