On 2023/10/19 16:30, Cédric Le Goater wrote:
> On 10/19/23 10:03, liulongfang wrote:
>> On 2023/10/16 23:17, Cédric Le Goater wrote:
>>> Hello Longfang,
>>>
>>> On 10/13/23 11:04, Longfang Liu wrote:
>>>> 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
>>>> |
>>>> +---<dev_name2>
>>>> +---migration
>>>> +--state
>>>>
>>>> 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".
>>>>
>>>> Signed-off-by: Longfang Liu <liulongfang@xxxxxxxxxx>
>>>> ---
>>>> drivers/vfio/Kconfig | 10 +++++
>>>> drivers/vfio/Makefile | 1 +
>>>> drivers/vfio/debugfs.c | 90 +++++++++++++++++++++++++++++++++++++++
>>>> drivers/vfio/vfio.h | 14 ++++++
>>>> drivers/vfio/vfio_main.c | 14 +++++-
>>>> include/linux/vfio.h | 7 +++
>>>> include/uapi/linux/vfio.h | 1 +
>>>> 7 files changed, 135 insertions(+), 2 deletions(-)
>>>> create mode 100644 drivers/vfio/debugfs.c
>>>>
>>>> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
>>>> index 6bda6dbb4878..ceae52fd7586 100644
>>>> --- a/drivers/vfio/Kconfig
>>>> +++ b/drivers/vfio/Kconfig
>>>> @@ -80,6 +80,16 @@ config VFIO_VIRQFD
>>>> select EVENTFD
>>>> default n
>>>> +config VFIO_DEBUGFS
>>>> + bool "Export VFIO internals in DebugFS"
>>>> + depends on DEBUG_FS
>>>> + help
>>>> + Allows exposure of VFIO device internals. This option enables
>>>> + the use of debugfs by VFIO drivers as required. The device can
>>>> + cause the VFIO code create a top-level debug/vfio directory
>>>> + during initialization, and then populate a subdirectory with
>>>> + entries as required.
>>>> +
>>>> source "drivers/vfio/pci/Kconfig"
>>>> source "drivers/vfio/platform/Kconfig"
>>>> source "drivers/vfio/mdev/Kconfig"
>>>> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
>>>> index c82ea032d352..d43a699d55b1 100644
>>>> --- a/drivers/vfio/Makefile
>>>> +++ b/drivers/vfio/Makefile
>>>> @@ -8,6 +8,7 @@ vfio-$(CONFIG_VFIO_GROUP) += group.o
>>>> vfio-$(CONFIG_IOMMUFD) += iommufd.o
>>>> vfio-$(CONFIG_VFIO_CONTAINER) += container.o
>>>> vfio-$(CONFIG_VFIO_VIRQFD) += virqfd.o
>>>> +vfio-$(CONFIG_VFIO_DEBUGFS) += debugfs.o
>>>> obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
>>>> obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
>>>> diff --git a/drivers/vfio/debugfs.c b/drivers/vfio/debugfs.c
>>>> new file mode 100644
>>>> index 000000000000..ae53d6110f47
>>>> --- /dev/null
>>>> +++ b/drivers/vfio/debugfs.c
>>>> @@ -0,0 +1,90 @@
>>>> +// 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;
>>>> +
>>>> + BUILD_BUG_ON(VFIO_DEVICE_STATE_NR !=
>>>> + VFIO_DEVICE_STATE_PRE_COPY_P2P + 1);
>>>> +
>>>> + ret = vdev->mig_ops->migration_get_state(vdev, &state);
>>>> + if (ret)
>>>> + return -EINVAL;
>>>> +
>>>> + switch (state) {
>>>> + case VFIO_DEVICE_STATE_ERROR:
>>>> + seq_printf(seq, "%s\n", "ERROR");
>>>> + break;
>>>> + case VFIO_DEVICE_STATE_STOP:
>>>> + seq_printf(seq, "%s\n", "STOP");
>>>> + break;
>>>> + 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_RESUMING:
>>>> + seq_printf(seq, "%s\n", "RESUMING");
>>>> + break;
>>>> + case VFIO_DEVICE_STATE_RUNNING_P2P:
>>>> + seq_printf(seq, "%s\n", "RUNNING_P2P");
>>>> + break;
>>>> + case VFIO_DEVICE_STATE_PRE_COPY:
>>>> + seq_printf(seq, "%s\n", "PRE_COPY");
>>>> + break;
>>>> + case VFIO_DEVICE_STATE_PRE_COPY_P2P:
>>>> + seq_printf(seq, "%s\n", "PRE_COPY_P2P");
>>>> + break;
>>>> + default:
>>>> + seq_printf(seq, "%s\n", "Invalid");
>>>
>>> seq_puts() is more appropriate than seq_printf() above.
>>>
>>
>> There is no difference between seq_puts() and seq_printf() here,
>> no need to modify it.
>
> seq_puts is simply preferred for unformatted output.
>
I think there is nothing wrong with using "seq_printf".
>>> I would suggest to add an array or some helper, that the VFIO drivers
>>> could use to debug the migration flow with pr_* primitives. It can be
>>> done later.
>>>
>>
>> If you want to debug this migration process in the VFIO driver,
>> you can refer to vdev->mig_ops->migration_get_state() to read the status.
>>
>>>
>>>> + }
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +void vfio_device_debugfs_init(struct vfio_device *vdev)
>>>> +{
>>>> + struct device *dev = &vdev->device;
>>>> +
>>>> + vdev->debug_root = debugfs_create_dir(dev_name(vdev->dev), vfio_debugfs_root);
>>>> +
>>>> + if (vdev->mig_ops) {
>>>> + struct dentry *vfio_dev_migration = NULL;
>>>
>>> mig_dir maybe ?
>>>
>>
>> "vfio_dev_migration " will not affect the readability of the code.
>>
>>> It would be easier to understand the nature of the variable IMHO.
>>>
>>>> +
>>>> + 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.h b/drivers/vfio/vfio.h
>>>> index 307e3f29b527..bde84ad344e5 100644
>>>> --- a/drivers/vfio/vfio.h
>>>> +++ b/drivers/vfio/vfio.h
>>>> @@ -448,4 +448,18 @@ static inline void vfio_device_put_kvm(struct vfio_device *device)
>>>> }
>>>> #endif
>>>> +#ifdef CONFIG_VFIO_DEBUGFS
>>>> +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_VFIO_DEBUGFS */
>>>> +
>>>> #endif
>>>> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
>>>> index e31e1952d7b8..9aec4c22f051 100644
>>>> --- a/drivers/vfio/vfio_main.c
>>>> +++ b/drivers/vfio/vfio_main.c
>>>> @@ -309,7 +309,6 @@ static int __vfio_register_dev(struct vfio_device *device,
>>>> /* Refcounting can't start until the driver calls register */
>>>> refcount_set(&device->refcount, 1);
>>>> -
>>>
>>> superfluous change.
>>>
>>
>> A blank line here is to separate it from the comment above.
>> Makes it easier to be read.
>>
>>>> vfio_device_group_register(device);
>>>> return 0;
>>>> @@ -320,7 +319,15 @@ static int __vfio_register_dev(struct vfio_device *device,
>>>> int vfio_register_group_dev(struct vfio_device *device)
>>>> {
>>>> - return __vfio_register_dev(device, VFIO_IOMMU);
>>>> + int ret;
>>>> +
>>>> + ret = __vfio_register_dev(device, VFIO_IOMMU);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + vfio_device_debugfs_init(device);
>>>
>>> Can it be called from __vfio_register_dev() instead ? and mdev devices
>>> would get debugfs support also.
>>>
>>
>> This is for symmetry in function calls.
>> The need for symmetry was mentioned in the previous review.
>
> yes. But this is also exluding the mdev devices which is a large VFIO family.
>
Here it is symmetrically encoded like this. Are there any problems when using it in mdev?
Thanks,
Longfang.
> Thanks,
>
> C.
>
>>
>>> Thanks,
>>>
>>> C.
>>>
>> Thanks,
>> Longfang.
>>
>>>> +
>>>> + return 0;
>>>> }
>>>> EXPORT_SYMBOL_GPL(vfio_register_group_dev);
>>>> @@ -378,6 +385,7 @@ void vfio_unregister_group_dev(struct vfio_device *device)
>>>> }
>>>> }
>>>> + vfio_device_debugfs_exit(device);
>>>> /* Balances vfio_device_set_group in register path */
>>>> vfio_device_remove_group(device);
>>>> }
>>>> @@ -1676,6 +1684,7 @@ static int __init vfio_init(void)
>>>> if (ret)
>>>> goto err_alloc_dev_chrdev;
>>>> + vfio_debugfs_create_root();
>>>> pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
>>>> return 0;
>>>> @@ -1691,6 +1700,7 @@ static int __init vfio_init(void)
>>>> static void __exit vfio_cleanup(void)
>>>> {
>>>> + vfio_debugfs_remove_root();
>>>> ida_destroy(&vfio.device_ida);
>>>> vfio_cdev_cleanup();
>>>> class_destroy(vfio.device_class);
>>>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>>>> index 454e9295970c..769d7af86225 100644
>>>> --- a/include/linux/vfio.h
>>>> +++ b/include/linux/vfio.h
>>>> @@ -69,6 +69,13 @@ struct vfio_device {
>>>> u8 iommufd_attached:1;
>>>> #endif
>>>> u8 cdev_opened:1;
>>>> +#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
>>>> };
>>>> /**
>>>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>>>> index 7f5fb010226d..2b68e6cdf190 100644
>>>> --- a/include/uapi/linux/vfio.h
>>>> +++ b/include/uapi/linux/vfio.h
>>>> @@ -1219,6 +1219,7 @@ enum vfio_device_mig_state {
>>>> VFIO_DEVICE_STATE_RUNNING_P2P = 5,
>>>> VFIO_DEVICE_STATE_PRE_COPY = 6,
>>>> VFIO_DEVICE_STATE_PRE_COPY_P2P = 7,
>>>> + VFIO_DEVICE_STATE_NR,
>>>> };
>>>> /**
>>>
>>> .
>>>
>>
>
> .
>
