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Message-ID: <d4a2f596-13c9-f3d3-3bbd-ee773f026341@huawei.com>
Date: Thu, 19 Oct 2023 16:03:24 +0800
From: liulongfang <liulongfang@...wei.com>
To: Cédric Le Goater <clegoate@...hat.com>,
<alex.williamson@...hat.com>, <jgg@...dia.com>,
<shameerali.kolothum.thodi@...wei.com>,
<jonathan.cameron@...wei.com>
CC: <bcreeley@....com>, <kvm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <linuxarm@...neuler.org>
Subject: Re: [PATCH v17 1/2] vfio/migration: Add debugfs to live migration
driver
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@...wei.com>
>> ---
>> 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.
> 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.
> 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,
>> };
>> /**
>
> .
>
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