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From:   Longfang Liu <liulongfang@huawei.com>
To:     <alex.williamson@redhat.com>, <jgg@nvidia.com>,
        <shameerali.kolothum.thodi@huawei.com>,
        <jonathan.cameron@huawei.com>
CC:     <cohuck@redhat.com>, <linux-kernel@vger.kernel.org>,
        <linuxarm@openeuler.org>, <liulongfang@huawei.com>
Subject: [PATCH v10 1/5] vfio/migration: Add debugfs to live migration driver
Date:   Sat, 8 Apr 2023 15:42:20 +0800
Message-ID: <20230408074224.62608-2-liulongfang@huawei.com>
In-Reply-To: <20230408074224.62608-1-liulongfang@huawei.com>
References: <20230408074224.62608-1-liulongfang@huawei.com>
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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                     |
    |                                           |
    |                                           |
    +---+----------------------------+----------+
        |      ^                     |      ^
        |      |                     |      |
        |      |                     |      |
        v      |                     v      |
     +---------+--+               +---------+--+
     |src vfio_dev|               |dst vfio_dev|
     +--+---------+               +--+---------+
        |      ^                     |      ^
        |      |                     |      |
        v      |                     |      |
   +-----------+----+           +-----------+----+
   |src dev debugfs |           |dst dev debugfs |
   +----------------+           +----------------+

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.

   vfio
    |
    +---<dev_name1>
    |    +---migration
    |        +--state
    |        +--hisi_acc
    |            +--attr
    |            +--data
    |            +--debug
    |
    +---<dev_name2>
         +---migration
             +--state
             +--hisi_acc
                 +--attr
                 +--data
                 +--debug

debugfs will create a public root directory "vfio" file.
then create a dev_name() file for each live migration device.
First, create a unified state acquisition file of "migration"
in this device directory.
Then, create a public live migration state lookup file "state"
Finally, create a directory file based on the device type,
and then create the device's own debugging files under
this directory file.

Here, HiSilicon accelerator creates three debug files:
attr: used to obtain the attribute parameters of the
current live migration device.
data: used to get the live migration data of the current
live migration device.
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 | 78 +++++++++++++++++++++++++++++++++++++
 drivers/vfio/vfio_main.c    |  9 ++++-
 include/linux/vfio.h        |  8 ++++
 5 files changed, 109 insertions(+), 2 deletions(-)
 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..8e5cafa6aa3a 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_device_debugfs_init(struct vfio_device *vdev);
+void vfio_device_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_device_debugfs_init(struct vfio_device *vdev) { }
+static inline void vfio_device_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..7bff30f76bd9
--- /dev/null
+++ b/drivers/vfio/vfio_debugfs.c
@@ -0,0 +1,78 @@
+// 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_device_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)
+		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_device_debugfs_init(struct vfio_device *vdev)
+{
+	struct dentry *vfio_dev_migration = NULL;
+	struct device *dev = &vdev->device;
+
+	vdev->debug_root = debugfs_create_dir(dev_name(vdev->dev), vfio_debugfs_root);
+	vfio_dev_migration = debugfs_create_dir("migration", vdev->debug_root);
+
+	debugfs_create_devm_seqfile(dev, "state", vfio_dev_migration,
+				  vfio_device_state_read);
+}
+
+void vfio_device_debugfs_exit(struct vfio_device *vdev)
+{
+	debugfs_remove_recursive(vdev->debug_root);
+}
+
+void vfio_debugfs_create_root(void)
+{
+	vfio_debugfs_root = debugfs_create_dir("vfio", NULL);
+}
+
+void vfio_debugfs_remove_root(void)
+{
+	debugfs_remove_recursive(vfio_debugfs_root);
+	vfio_debugfs_root = NULL;
+}
+
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 3a597e799918..e9ddf6612e44 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -274,7 +274,8 @@ static int __vfio_register_dev(struct vfio_device *device,
 
 	/* Refcounting can't start until the driver calls register */
 	refcount_set(&device->refcount, 1);
-
+	if (device->mig_ops)
+		vfio_device_debugfs_init(device);
 	vfio_device_group_register(device);
 
 	return 0;
@@ -331,6 +332,8 @@ void vfio_unregister_group_dev(struct vfio_device *device)
 		}
 	}
 
+	if (device->mig_ops)
+		vfio_device_debugfs_exit(device);
 	vfio_device_group_unregister(device);
 
 	/* Balances device_add in register path */
@@ -1407,7 +1410,10 @@ static int __init vfio_init(void)
 		goto err_dev_class;
 	}
 
+
+	vfio_debugfs_create_root();
 	pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
+
 	return 0;
 
 err_dev_class:
@@ -1425,6 +1431,7 @@ 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