Re: [PATCH v11 1/4] vfio/migration: Add debugfs to live migration driver
From: liulongfang
Date: Sun Jul 23 2023 - 22:42:16 EST
On 2023/7/19 1:45, Cédric Le Goater Wrote:
> On 6/30/23 11:24, liulongfang wrote:
>> From: Longfang Liu <liulongfang@xxxxxxxxxx>
>>
>> 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
>> | +--save
>> | +--io_test
>> |
>> +---<dev_name2>
>> +---migration
>> +--state
>> +--hisi_acc
>> +--attr
>> +--data
>> +--save
>> +--io_test
>>
>> 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 export the attribute parameters of the
>> current live migration device.
>> data: used to export the live migration data of the current
>> live migration device.
>> save: used to read the current live migration device's data
>> and save it to the driver.
>> io_test: used to test the IO read and write for the driver.
>>
>> 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@xxxxxxxxxx>
>> ---
>> drivers/vfio/Makefile | 1 +
>> drivers/vfio/vfio.h | 14 +++++++
>> drivers/vfio/vfio_debugfs.c | 78 +++++++++++++++++++++++++++++++++++++
>> drivers/vfio/vfio_main.c | 9 ++++-
>> include/linux/vfio.h | 7 ++++
>> 5 files changed, 108 insertions(+), 1 deletion(-)
>> create mode 100644 drivers/vfio/vfio_debugfs.c
>>
>> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
>> index 66f418aef5a9..6829c58210dc 100644
>> --- a/drivers/vfio/Makefile
>> +++ b/drivers/vfio/Makefile
>> @@ -7,6 +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
>> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
>> index 7b19c621e0e6..729c52ef579a 100644
>> --- a/drivers/vfio/vfio.h
>> +++ b/drivers/vfio/vfio.h
>> @@ -264,4 +264,18 @@ 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;
>
> This could be external to all VFIO. See comment below.
>
>> +
>> +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);
>> +}
>
> I would simply use :
>
> if (IS_ENABLED(CONFIG_DEBUG_FS))
> debugfs_remove_recursive(vdev->debug_root);
>
> where vfio_device_debugfs_exit() is called.
>
These functions have been processed by CONFIG_DEBUG_FS in vfio.h.
The effect is almost the same.
>> +
>> +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;
> ditto.
>
ditto.
>> +}
>> +
>> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
>> index f0ca33b2e1df..18d050ec9a12 100644
>> --- a/drivers/vfio/vfio_main.c
>> +++ b/drivers/vfio/vfio_main.c
>> @@ -282,7 +282,8 @@ 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);
>
> I think we should prepare ground for more debugfs files than just migration
> related things. Migration is clearly a very good candidate, but there could
> be more. I have a couple out of tree patches to collect statistics on VMA
> usage and resets for instance which could be included.
>
>
> Thanks,
>
> C.
OK, this suggestion of yours is very good.
I can put this judgment processing into vfio_device_debugfs_init().
If your patch needs to add debugfs, you can add it in vfio_device_debugfs_init().
Thanks,
Longfang.
>
>> vfio_device_group_register(device);
>> return 0;
>> @@ -339,6 +340,8 @@ 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 */
>> @@ -1415,7 +1418,10 @@ 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:
>> @@ -1433,6 +1439,7 @@ 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 2c137ea94a3e..a114b430be31 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -62,6 +62,13 @@ struct vfio_device {
>> struct iommufd_device *iommufd_device;
>> 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
>> };
>> /**
>
> .
>