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Message-ID: <d541ba02-a8d1-dc8e-a725-4ee82b0c44bb@huawei.com>
Date: Fri, 22 Sep 2023 14:19:36 +0800
From: liulongfang <liulongfang@...wei.com>
To: Alex Williamson <alex.williamson@...hat.com>
CC: <jgg@...dia.com>, <shameerali.kolothum.thodi@...wei.com>,
<jonathan.cameron@...wei.com>, <bcreeley@....com>,
<kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linuxarm@...neuler.org>
Subject: Re: [PATCH v15 1/2] vfio/migration: Add debugfs to live migration
driver
On 2023/9/16 5:00, Alex Williamson wrote:
> On Fri, 1 Sep 2023 10:36:05 +0800
> liulongfang <liulongfang@...wei.com> wrote:
>
>> From: Longfang Liu <liulongfang@...wei.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 |
>> | |
>> | |
>> +---+----------------------------+----------+
>> | ^ | ^
>> | | | |
>> | | | |
>> 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"
>> Finally, create a directory file based on the device type,
>> and then create the device's own debugging files under
>> this directory file.
>>
>> Signed-off-by: Longfang Liu <liulongfang@...wei.com>
>> ---
>> drivers/vfio/Makefile | 1 +
>> drivers/vfio/vfio.h | 14 +++++++
>> drivers/vfio/vfio_debugfs.c | 80 +++++++++++++++++++++++++++++++++++++
>> drivers/vfio/vfio_main.c | 5 ++-
>> include/linux/vfio.h | 7 ++++
>> 5 files changed, 106 insertions(+), 1 deletion(-)
>> create mode 100644 drivers/vfio/vfio_debugfs.c
>>
>> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
>> index c82ea032d352..7934ac829989 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-$(CONFIG_DEBUG_FS) += vfio_debugfs.o
>>
>> obj-$(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 307e3f29b527..09b00757d0bb 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_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..cd6c01437475
>> --- /dev/null
>> +++ b/drivers/vfio/vfio_debugfs.c
>> @@ -0,0 +1,80 @@
>> +// 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", "RUNNING_P2P");
>> + break;
>> + case VFIO_DEVICE_STATE_ERROR:
>> + seq_printf(seq, "%s\n", "ERROR");
>
> Please order these the same as enum vfio_device_mig_state, we're also
> missing a couple states, ie. PRE_COPY and PRE_COPY_P2P. Can we use any
OK, I'll add them to the next version.
> compiler tricks to create a build error when these are out of sync?
>When these states are out of range, they should enter "default" processing.
>> + 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;
>
> Nit, both of these could be defined within the scope of the mig_ops
> test below.
>
"vfio_dev_migration" can be placed under mig_ops, but "dev" is public.
Also, there should be no problem declaring variables like this.
>> +
>> + vdev->debug_root = debugfs_create_dir(dev_name(vdev->dev), vfio_debugfs_root);
>> +
>> + if (vdev->mig_ops) {
>> + 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 cfad824d9aa2..8a7456f89842 100644
>> --- a/drivers/vfio/vfio_main.c
>> +++ b/drivers/vfio/vfio_main.c
>> @@ -309,7 +309,7 @@ static int __vfio_register_dev(struct vfio_device *device,
>>
>> /* Refcounting can't start until the driver calls register */
>> refcount_set(&device->refcount, 1);
>> -
>> + vfio_device_debugfs_init(device);
>> vfio_device_group_register(device);
>>
>> return 0;
>> @@ -378,6 +378,7 @@ 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);
>> }
>
> init/exit calls should try to be symmetric, if we call init before
> vfio_device_group_register() then we should call exit after
> vfio_device_group_unregister(). In this case, why shouldn't init be
> the last call in __vfio_register_dev() and exit the first call in
> vfio_unregister_group_dev()?
>
OK, I would put vfio_device_debugfs_init() into vfio_device_group_register().
>> @@ -1662,6 +1663,7 @@ 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;
>>
>> @@ -1684,6 +1686,7 @@ static void __exit vfio_cleanup(void)
>> vfio_virqfd_exit();
>> vfio_group_cleanup();
>> xa_destroy(&vfio_device_set_xa);
>> + vfio_debugfs_remove_root();
>> }
>
> Same, if we create it last, let's remove it first. The above creates
> it last and removes it last. Thanks,
>
OK, I will adjust the order of vfio_debugfs_remove_root() in vfio_cleanup().
Thanks,
Longfang.
> Alex
>
>>
>> module_init(vfio_init);
>> 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
>> };
>>
>> /**
>
> .
>
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