Re: [PATCH v4 1/5] vfio/migration: Add debugfs to live migration driver

liulongfang
2022-12-05T13:43:11Z

On 2022/12/2 18:02, Shameerali Kolothum Thodi wrote:
>
>
>> -----Original Message-----
>> From: liulongfang
>> Sent: 02 December 2022 09:26
>> To: alex.williamson@redhat.com; jgg@nvidia.com; Shameerali Kolothum
>> Thodi <shameerali.kolothum.thodi@huawei.com>; john.garry@huawei.com
>> Cc: cohuck@redhat.com; linux-kernel@vger.kernel.org;
>> linuxarm@openeuler.org; liulongfang <liulongfang@huawei.com>
>> Subject: [PATCH v4 1/5] vfio/migration: Add debugfs to live migration driver
>>
>> 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 VF | | dst VF |
>> +-+------+ +-+------+
>> | ^ | ^
>> v | v |
>> +-------+-+------+ +-------+-+------+
>> | |state | | |state |
>> | +--------+ | +--------+
>> |Debugfs|mig_data| |Debugfs|mig_data|
>> | +--------+ | +--------+
>> | |mig_attr| | |mig_attr|
>> +-------+--------+ +-------+--------+
>> | debug_root | | debug_root |
>> +-------+--------+ +-------+--------+
>>
>> debugfs will create a public root directory "vfio_mig" file.
>> then create a "debug_root" file and three debug files for each
>> live migration VF device.
>> state file: used to get the status of the live migration device.
>> mig_data file: used to get the migration data of the live migration device
>> mig_attr file: used to get device attributes of the live migration device
>> debug_root: used to create your own custom debug files for live
>> migration device drivers.
>>
>> 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/pci/Makefile | 4 +
>> drivers/vfio/pci/vfio_pci_core.c | 3 +
>> drivers/vfio/pci/vfio_pci_debugfs.c | 142 ++++++++++++++++++++++++++++
>> drivers/vfio/pci/vfio_pci_debugfs.h | 32 +++++++
>> include/linux/vfio.h | 12 +++
>> 5 files changed, 193 insertions(+)
>> create mode 100644 drivers/vfio/pci/vfio_pci_debugfs.c
>> create mode 100644 drivers/vfio/pci/vfio_pci_debugfs.h
>>
>> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
>> index 24c524224da5..efe032623664 100644
>> --- a/drivers/vfio/pci/Makefile
>> +++ b/drivers/vfio/pci/Makefile
>> @@ -4,6 +4,10 @@ vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o
>> vfio_pci_rdwr.o vfio_pci_con
>> vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV_KVM) += vfio_pci_zdev.o
>> obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
>>
>> +ifneq ($(CONFIG_DEBUG_FS),)
>> + vfio-pci-core-y += vfio_pci_debugfs.o
>> +endif
>> +
>> vfio-pci-y := vfio_pci.o
>> vfio-pci-$(CONFIG_VFIO_PCI_IGD) += vfio_pci_igd.o
>> obj-$(CONFIG_VFIO_PCI) += vfio-pci.o
>> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
>> index 189d4930c276..1d6dd61aef7d 100644
>> --- a/drivers/vfio/pci/vfio_pci_core.c
>> +++ b/drivers/vfio/pci/vfio_pci_core.c
>> @@ -28,6 +28,7 @@
>> #include <linux/nospec.h>
>> #include <linux/sched/mm.h>
>>
>> +#include "vfio_pci_debugfs.h"
>> #include "vfio_pci_priv.h"
>>
>> #define DRIVER_AUTHOR "Alex Williamson
>> <alex.williamson@redhat.com>"
>> @@ -2548,11 +2549,13 @@
>> EXPORT_SYMBOL_GPL(vfio_pci_core_set_params);
>>
>> static void vfio_pci_core_cleanup(void)
>> {
>> + vfio_pci_debugfs_remove_root();
>> vfio_pci_uninit_perm_bits();
>> }
>>
>> static int __init vfio_pci_core_init(void)
>> {
>> + vfio_pci_debugfs_create_root();
>> /* Allocate shared config space permission data used by all devices */
>> return vfio_pci_init_perm_bits();
>> }
>> diff --git a/drivers/vfio/pci/vfio_pci_debugfs.c
>> b/drivers/vfio/pci/vfio_pci_debugfs.c
>> new file mode 100644
>> index 000000000000..94a42869539e
>> --- /dev/null
>> +++ b/drivers/vfio/pci/vfio_pci_debugfs.c
>> @@ -0,0 +1,142 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2022, HiSilicon Ltd.
>> + */
>> +
>> +#include <linux/pci.h>
>> +#include <linux/vfio_pci_core.h>
>> +
>> +#include "vfio_pci_debugfs.h"
>> +
>> +#define VFIO_DEV_BUF_LEN 4096
>> +static struct dentry *vfio_pci_debugfs_root;
>> +
>> +static ssize_t vfio_pci_vf_data_dump(struct file *filp, char __user *buffer,
>> + size_t count, loff_t *pos)
>> +{
>> + struct vfio_device *vdev = filp->private_data;
>> + char tbuf[VFIO_DEV_BUF_LEN];
>> + int len;
>> +
>> + if (!vdev->mig_ops || !vdev->mig_ops->migration_get_data) {
>> + dev_err(vdev->dev, "device not support get data!\n");
>> + return -EINVAL;
>> + }
>> +
>> + len = vdev->mig_ops->migration_get_data(vdev, tbuf);
>> +
>> + return simple_read_from_buffer(buffer, count, pos, tbuf, len);
>> +}
>> +
>> +static const struct file_operations vfio_vf_data_fops = {
>> + .owner = THIS_MODULE,
>> + .open = simple_open,
>> + .read = vfio_pci_vf_data_dump,
>> +};
>> +
>> +static ssize_t vfio_pci_vf_attr_show(struct file *filp, char __user *buffer,
>> + size_t count, loff_t *pos)
>> +{
>> + struct vfio_device *vdev = filp->private_data;
>> + char tbuf[VFIO_DEV_BUF_LEN];
>> + int len;
>> +
>> + if (!vdev->mig_ops || !vdev->mig_ops->migration_get_attr) {
>> + dev_err(vdev->dev, "device not support get attribute!\n");
>> + return -EINVAL;
>> + }
>> +
>> + len = vdev->mig_ops->migration_get_attr(vdev, tbuf);
>> +
>> + return simple_read_from_buffer(buffer, count, pos, tbuf, len);
>> +}
>> +
>> +static const struct file_operations vfio_vf_attr_fops = {
>> + .owner = THIS_MODULE,
>> + .open = simple_open,
>> + .read = vfio_pci_vf_attr_show,
>> +};
>> +
>> +static ssize_t vfio_pci_vf_state_read(struct file *filp, char __user *buffer,
>> + size_t count, loff_t *pos)
>> +{
>> + struct vfio_device *vdev = filp->private_data;
>> + char buf[VFIO_DEV_DBG_LEN];
>> + enum vfio_device_mig_state state;
>> + int len;
>> +
>> + (void)vdev->mig_ops->migration_get_state(vdev, &state);
>> + switch (state) {
>> + case VFIO_DEVICE_STATE_RUNNING:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "RUNNING\n");
>> + break;
>> + case VFIO_DEVICE_STATE_STOP_COPY:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "STOP_COPY\n");
>> + break;
>> + case VFIO_DEVICE_STATE_STOP:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "STOP\n");
>> + break;
>> + case VFIO_DEVICE_STATE_RESUMING:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "RESUMING\n");
>> + break;
>> + case VFIO_DEVICE_STATE_RUNNING_P2P:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "RESUMING_P2P\n");
>> + break;
>> + case VFIO_DEVICE_STATE_ERROR:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "ERROR\n");
>> + break;
>> + default:
>> + len = scnprintf(buf, VFIO_DEV_DBG_LEN, "%s\n",
>> + "Invalid\n");
>> + }
>> +
>> + return simple_read_from_buffer(buffer, count, pos, buf, len);
>> +}
>> +
>> +static const struct file_operations vfio_vf_state_fops = {
>> + .owner = THIS_MODULE,
>> + .open = simple_open,
>> + .read = vfio_pci_vf_state_read,
>> +};
>> +
>> +void vfio_pci_vf_debugfs_init(struct vfio_device *vdev)
>> +{
>> + struct device *dev = vdev->dev;
>> +
>> + vdev->debug_root = debugfs_create_dir(dev_name(dev),
>> vfio_pci_debugfs_root);
>> + debugfs_create_file("state", 0444, vdev->debug_root,
>> + vdev, &vfio_vf_state_fops);
>> +
>> + debugfs_create_file("mig_data", 0444, vdev->debug_root,
>> + vdev, &vfio_vf_data_fops);
>> +
>> + debugfs_create_file("mig_attr", 0444, vdev->debug_root,
>> + vdev, &vfio_vf_attr_fops);
>
> I would probably avoid creating the mig_attr as well in the common code,
> retaining only the "state" and optional "mig_data" here.
>

In the live migration driver, in addition to the device state and device migration data,
the functional attributes of the migrating device should also be a common part.

Thanks,
Longfang.

>
> Thanks,
> Shameer
>
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_pci_vf_debugfs_init);
>> +
>> +void vfio_pci_vf_debugfs_exit(struct vfio_device *vdev)
>> +{
>> + debugfs_remove_recursive(vdev->debug_root);
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_pci_vf_debugfs_exit);
>> +
>> +void vfio_pci_debugfs_create_root(void)
>> +{
>> + vfio_pci_debugfs_root = debugfs_create_dir("vfio_mig", NULL);
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_pci_debugfs_create_root);
>> +
>> +void vfio_pci_debugfs_remove_root(void)
>> +{
>> + debugfs_remove_recursive(vfio_pci_debugfs_root);
>> + vfio_pci_debugfs_root = NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(vfio_pci_debugfs_remove_root);
>> +
>> diff --git a/drivers/vfio/pci/vfio_pci_debugfs.h
>> b/drivers/vfio/pci/vfio_pci_debugfs.h
>> new file mode 100644
>> index 000000000000..92031196a637
>> --- /dev/null
>> +++ b/drivers/vfio/pci/vfio_pci_debugfs.h
>> @@ -0,0 +1,32 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * vfio_pci_debugfs.h - VFIO migration debugfs interface
>> + *
>> + * Copyright (c) 2022, HiSilicon Ltd.
>> + *
>> + * Author: Longfang Liu <liulongfang@huawei.com>
>> + */
>> +
>> +#ifndef __VFIO_PCI_DEBUGFS_H
>> +#define __VFIO_PCI_DEBUGFS_H
>> +
>> +#include <linux/debugfs.h>
>> +#include <linux/vfio.h>
>> +
>> +#define VFIO_DEV_DBG_LEN 256
>> +
>> +#ifdef CONFIG_DEBUG_FS
>> +void vfio_pci_debugfs_create_root(void);
>> +void vfio_pci_debugfs_remove_root(void);
>> +
>> +void vfio_pci_vf_debugfs_init(struct vfio_device *vdev);
>> +void vfio_pci_vf_debugfs_exit(struct vfio_device *vdev);
>> +#else
>> +static inline void vfio_pci_debugfs_create_root(void) { }
>> +static inline void vfio_pci_debugfs_remove_root(void) { }
>> +
>> +static inline void vfio_pci_vf_debugfs_init(struct vfio_device *vdev) { }
>> +static inline void vfio_pci_vf_debugfs_exit(struct vfio_device *vdev) { }
>> +#endif /* CONFIG_DEBUG_FS */
>> +
>> +#endif /* __VFIO_PCI_DEBUGFS_H */
>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index 43b67e46a2cb..ee441ccdcc71 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -54,6 +54,12 @@ struct vfio_device {
>> struct completion comp;
>> struct list_head group_next;
>> struct list_head iommu_entry;
>> +
>> + /*
>> + * debug_root is a static property of the vfio_device
>> + * which must be set prior to registering the vfio_device.
>> + */
>> + struct dentry *debug_root;
>> };
>>
>> /**
>> @@ -110,6 +116,10 @@ struct vfio_device_ops {
>> * @migration_get_data_size: Optional callback to get the estimated data
>> * length that will be required to complete stop copy. It's
>> mandatory for
>> * VFIO_DEVICE_FEATURE_MIGRATION migration support.
>> + * @migration_get_data: Optional callback to get the migration data
>> + * that will be required by vfio debugfs.
>> + * @migration_get_attr: Optional callback to get the device attributes
>> + * that will be required by vfio debugfs.
>> */
>> struct vfio_migration_ops {
>> struct file *(*migration_set_state)(
>> @@ -119,6 +129,8 @@ struct vfio_migration_ops {
>> enum vfio_device_mig_state *curr_state);
>> int (*migration_get_data_size)(struct vfio_device *device,
>> unsigned long *stop_copy_length);
>> + int (*migration_get_data)(struct vfio_device *device, char *buffer);
>> + int (*migration_get_attr)(struct vfio_device *device, char *buffer);
>> };
>>
>> /**
>> --
>> 2.24.0
>
> .
>