[PATCH v8 1/5] vfio/migration: Add debugfs to live migration driver

[Longfang Liu <liulongfang@huawei.com>]

There are multiple devices, software and operational steps involved
in the process of live migration. An error occurred on any node may
cause the live migration operation to fail.
This complex process makes it very difficult to locate and analyze
the cause when the function fails.

In order to quickly locate the cause of the problem when the
live migration fails, I added a set of debugfs to the vfio
live migration driver.
                               +-------------------------------------------+
                               |                                           |
                               |                                           |
                               |                  QEMU                     |
                               |                                           |
                               |                                           |
                               +---+----------------------------+----------+
                                   |      ^                     |      ^
                                   |      |                     |      |
 +--------+                        |      |                     |      |
 |  vfio  |                        v      |                     v      |
 +--------+                     +---------+--+               +---------+--+
     ^                          |src vfio_dev|               |dst vfio_dev|
     |                          +--+---------+               +--+---------+
     |                             |      ^                     |      ^
     |                             |      |                     |      |
     |                             v      |                     |      |
     |  +-----------+         +-----------+----+                |      |
     +--+<bdf>file_x+<----+---+migration_attr  |                |      |
     |  +-----------+     |   +----------------+                |      |
     |                    +---+migration_data  |                |      |
     |                    |   +----------------+                |      |
     |                    +---+migration_debug |                |      |
     |                    |   +----------------+                |      |
     |                    |   +----------------+                |      |
     |                    +---+migration_state |                |      |
     |                        +----------------+                |      |
     |                                                          |      |
     |  +-----------+         +----------------+                |      |
     +--+<bdf>file_y|<----+---+migration_attr  |                |      |
        +-----------+     |   +----------------+                |      |
                          +---+migration_data  |                |      |
                          |   +----------------+<---------------+      |
                          +---+migration_debug |                       |
                          |   +----------------+                       |
                          |   +----------------+                       |
                          +---+migration_state +-----------------------+
                              +----------------+

The entire debugfs directory will be based on the definition of
the CONFIG_DEBUG_FS macro. If this macro is not enabled, the
interfaces in vfio.h will be empty definitions, and the creation
and initialization of the debugfs directory will not be executed.

debugfs will create a public root directory "vfio" file.
then create a device <bdf> named file for each live migration device.
First, create a unified state acquisition file of "migration_state"
in this device directory.
Then, create your own debugging files independently according to
the functional requirements of each device.

Here, HiSilicon accelerator creates three debug files:
migration_attr: used to obtain the attribute parameters of the
current live migration device.
migration_data: used to get the live migration data of the current
live migration device.
migration_debug: Used to debug the current live migration device
through commands.

The live migration function of the current device can be tested by
operating the debug files, and the functional status of the equipment
and software at each stage can be tested step by step without
performing the complete live migration function. And after the live
migration is performed, the migration device data of the live migration
can be obtained through the debug files.

Signed-off-by: Longfang Liu <liulongfang@huawei.com>
---
 drivers/vfio/Makefile       |  2 +-
 drivers/vfio/vfio.h         | 14 +++++++
 drivers/vfio/vfio_debugfs.c | 82 +++++++++++++++++++++++++++++++++++++
 drivers/vfio/vfio_main.c    |  5 +++
 include/linux/vfio.h        |  8 ++++
 5 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 drivers/vfio/vfio_debugfs.c

diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
index 70e7dcb302ef..1debcff31d30 100644
--- a/drivers/vfio/Makefile
+++ b/drivers/vfio/Makefile
@@ -7,7 +7,7 @@ vfio-y += vfio_main.o \
 vfio-$(CONFIG_IOMMUFD) += iommufd.o
 vfio-$(CONFIG_VFIO_CONTAINER) += container.o
 vfio-$(CONFIG_VFIO_VIRQFD) += virqfd.o
-
+vfio-$(CONFIG_DEBUG_FS) += vfio_debugfs.o
 obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
 obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
 obj-$(CONFIG_VFIO_PCI) += pci/
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index e9721d8424bc..66c00f97e9cc 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -258,4 +258,18 @@ static inline void vfio_device_put_kvm(struct vfio_device *device)
 }
 #endif
 
+#ifdef CONFIG_DEBUG_FS
+void vfio_debugfs_create_root(void);
+void vfio_debugfs_remove_root(void);
+
+void vfio_vf_debugfs_init(struct vfio_device *vdev);
+void vfio_vf_debugfs_exit(struct vfio_device *vdev);
+#else
+static inline void vfio_debugfs_create_root(void) { }
+static inline void vfio_debugfs_remove_root(void) { }
+
+static inline void vfio_vf_debugfs_init(struct vfio_device *vdev) { }
+static inline void vfio_vf_debugfs_exit(struct vfio_device *vdev) { }
+#endif /* CONFIG_DEBUG_FS */
+
 #endif
diff --git a/drivers/vfio/vfio_debugfs.c b/drivers/vfio/vfio_debugfs.c
new file mode 100644
index 000000000000..c5df1496fe0e
--- /dev/null
+++ b/drivers/vfio/vfio_debugfs.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, HiSilicon Ltd.
+ */
+
+#include <linux/device.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/vfio.h>
+#include "vfio.h"
+
+static struct dentry *vfio_debugfs_root;
+
+static int vfio_vf_state_read(struct seq_file *seq, void *data)
+{
+	struct device *vf_dev = seq->private;
+	struct vfio_device *vdev = container_of(vf_dev, struct vfio_device, device);
+	enum vfio_device_mig_state state;
+	int ret;
+
+	ret = vdev->mig_ops->migration_get_state(vdev, &state);
+	if (ret) {
+		dev_err(vf_dev, "failed to get device migration state");
+		return -EINVAL;
+	}
+
+	switch (state) {
+	case VFIO_DEVICE_STATE_RUNNING:
+		seq_printf(seq, "%s\n", "RUNNING");
+		break;
+	case VFIO_DEVICE_STATE_STOP_COPY:
+		seq_printf(seq, "%s\n", "STOP_COPY");
+		break;
+	case VFIO_DEVICE_STATE_STOP:
+		seq_printf(seq, "%s\n", "STOP");
+		break;
+	case VFIO_DEVICE_STATE_RESUMING:
+		seq_printf(seq, "%s\n", "RESUMING");
+		break;
+	case VFIO_DEVICE_STATE_RUNNING_P2P:
+		seq_printf(seq, "%s\n", "RESUMING_P2P");
+		break;
+	case VFIO_DEVICE_STATE_ERROR:
+		seq_printf(seq, "%s\n", "ERROR");
+		break;
+	default:
+		seq_printf(seq, "%s\n", "Invalid");
+	}
+
+	return 0;
+}
+
+void vfio_vf_debugfs_init(struct vfio_device *vdev)
+{
+	struct device *dev = &vdev->device;
+
+	vdev->debug_root = debugfs_create_dir(dev_name(vdev->dev), vfio_debugfs_root);
+
+	debugfs_create_devm_seqfile(dev, "migration_state", vdev->debug_root,
+				  vfio_vf_state_read);
+}
+EXPORT_SYMBOL_GPL(vfio_vf_debugfs_init);
+
+void vfio_vf_debugfs_exit(struct vfio_device *vdev)
+{
+	debugfs_remove_recursive(vdev->debug_root);
+}
+EXPORT_SYMBOL_GPL(vfio_vf_debugfs_exit);
+
+void  vfio_debugfs_create_root(void)
+{
+	vfio_debugfs_root = debugfs_create_dir("vfio", NULL);
+}
+EXPORT_SYMBOL_GPL(vfio_debugfs_create_root);
+
+void  vfio_debugfs_remove_root(void)
+{
+	debugfs_remove_recursive(vfio_debugfs_root);
+	vfio_debugfs_root = NULL;
+}
+EXPORT_SYMBOL_GPL(vfio_debugfs_remove_root);
+
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 3a597e799918..09772fd3a396 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -1408,6 +1408,9 @@ static int __init vfio_init(void)
 	}
 
 	pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
+
+	vfio_debugfs_create_root();
+
 	return 0;
 
 err_dev_class:
@@ -1425,6 +1428,8 @@ static void __exit vfio_cleanup(void)
 	vfio_virqfd_exit();
 	vfio_group_cleanup();
 	xa_destroy(&vfio_device_set_xa);
+
+	vfio_debugfs_remove_root();
 }
 
 module_init(vfio_init);
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 93134b023968..fa6b898ebb58 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -63,6 +63,14 @@ struct vfio_device {
 	struct iommufd_ctx *iommufd_ictx;
 	bool iommufd_attached;
 #endif
+
+#ifdef CONFIG_DEBUG_FS
+	/*
+	 * debug_root is a static property of the vfio_device
+	 * which must be set prior to registering the vfio_device.
+	 */
+	struct dentry *debug_root;
+#endif
 };
 
 /**
-- 
2.24.0