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SubjectRe: [PATCH v5 1/5] vfio/migration: Add debugfs to live migration driver
On Sat, Dec 17, 2022 at 02:32:44PM +0800, 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 VF | | dst VF |
> +-+------+ +-+------+
> | ^ | ^
> v | v |
> +-------+-+------+ +-------+-+------+
> |Debugfs|state | |Debugfs|state |
> +-------+--------+ +-------+--------+
> | debug_root | | debug_root |
> +-------+--------+ +-------+--------+
>
> debugfs will create a public root directory "vfio_mig" file.
> then create a "debug_root" file for each live migration VF device.
> state file: used to get the status 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 | 76 +++++++++++++++++++++++++++++
> drivers/vfio/pci/vfio_pci_debugfs.h | 30 ++++++++++++
> include/linux/vfio.h | 6 +++
> 5 files changed, 119 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

This is now how makefile should be written

vfio-pci-core-$(CONFIG_DEBUG_FS) += vfio_pci_debugfs.o

> +static int vfio_pci_vf_state_read(struct seq_file *seq, void *data)
> +{
> + struct device *vf_dev = seq->private;
> + struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
> + struct vfio_device *vdev = &core_device->vdev;
> + enum vfio_device_mig_state state;
> +
> + (void)vdev->mig_ops->migration_get_state(vdev, &state);

Do not use (void) like this, and why not handle the error?

> + 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_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_devm_seqfile(dev, "state", vdev->debug_root,
> + vfio_pci_vf_state_read);
> +}
> +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);

Why are these exported symbols? The core code should handle this on
its own.

If the device defines migration_get_state() then the debugfs should be
created.

Mabye you need an op to populate the driver's debugfs to also trigger
creating the directory

Jason

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