Re: [PATCH v11 4/4] Documentation: add debugfs description for vfio

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 30 Jun 2023 17:24:57 +0800
liulongfang <liulongfang@huawei.com> wrote:

> From: Longfang Liu <liulongfang@huawei.com>
> 
> 1.Add two debugfs document description file to help users understand
> how to use the accelerator live migration driver's debugfs.
> 2.Update the file paths that need to be maintained in MAINTAINERS
> 
> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
> ---
>  .../ABI/testing/debugfs-hisi-migration        | 32 +++++++++++++++++++
>  Documentation/ABI/testing/debugfs-vfio        | 25 +++++++++++++++
>  MAINTAINERS                                   |  2 ++
>  3 files changed, 59 insertions(+)
>  create mode 100644 Documentation/ABI/testing/debugfs-hisi-migration
>  create mode 100644 Documentation/ABI/testing/debugfs-vfio
> 
> diff --git a/Documentation/ABI/testing/debugfs-hisi-migration b/Documentation/ABI/testing/debugfs-hisi-migration
> new file mode 100644
> index 000000000000..0dfc7008a3e1
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-hisi-migration
> @@ -0,0 +1,32 @@
> +What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/data
> +Date:		June 2023
> +KernelVersion:  6.4

At best we'd be looking at introducing this for 6.6, where it might get
into mainline in late August for all of these.

> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	Read the live migration data of the vfio device.
> +		The output format of the data is defined by the live
> +		migration driver.

This attribute is specific to the hisi_acc driver, so should the data
be detailed here?

> +
> +What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/attr
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	Read the live migration attributes of the vfio device.
> +		The output format of the attributes is defined by the live
> +		migration driver.

Same here.

> +
> +What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/io_test
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	Trigger the HiSilicon accelerator device to perform
> +		the io test through the read operation, and directly output
> +		the test result.

This has essentially been reduced to reading the mailbox value AIUI,
should this simply document that and the resulting possible values?

> +
> +What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/save
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	Trigger the Hisilicon accelerator device to perform
> +		the state saving operation of live migration through the read
> +		operation, and directly output the operation result.

It's unclear to me why we need to parse a returned string from the
debugfs seq file rather than read returns zero on success or errno on
failure.

> +
> diff --git a/Documentation/ABI/testing/debugfs-vfio b/Documentation/ABI/testing/debugfs-vfio
> new file mode 100644
> index 000000000000..e2132a2f602b
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-vfio
> @@ -0,0 +1,25 @@
> +What:		/sys/kernel/debug/vfio
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	This debugfs file directory is used for debugging
> +		of vfio devices.
> +		Each device can create a device subdirectory under this
> +		directory by referencing the public registration interface.

This suggests it's the device driver's responsibility to create those
subdirectories, but we've delegated that to the core currently.  Maybe
this is suggesting that each driver can create a driver subdirectory
under the core created device directory?

Thanks,
Alex

> +
> +What:		/sys/kernel/debug/vfio/<device>/migration
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	This debugfs file directory is used for debugging
> +		of vfio devices that support live migration.
> +		The debugfs of each vfio device that supports live migration
> +		could be created under this directory.
> +
> +What:		/sys/kernel/debug/vfio/<device>/migration/state
> +Date:		June 2023
> +KernelVersion:  6.4
> +Contact:	Longfang Liu <liulongfang@huawei.com>
> +Description:	Read the live migration status of the vfio device.
> +		The status of these live migrations includes:
> +		ERROR, RUNNING, STOP, STOP_COPY, RESUMING.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index ce6ac552d8f6..bdd6a5e7350f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22098,6 +22098,7 @@ L:	kvm@vger.kernel.org
>  S:	Maintained
>  T:	git https://github.com/awilliam/linux-vfio.git
>  F:	Documentation/ABI/testing/sysfs-devices-vfio-dev
> +F:	Documentation/ABI/testing/debugfs-vfio
>  F:	Documentation/driver-api/vfio.rst
>  F:	drivers/vfio/
>  F:	include/linux/vfio.h
> @@ -22115,6 +22116,7 @@ M:	Longfang Liu <liulongfang@huawei.com>
>  M:	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
>  L:	kvm@vger.kernel.org
>  S:	Maintained
> +F:	Documentation/ABI/testing/debugfs-hisi-migration
>  F:	drivers/vfio/pci/hisilicon/
>  
>  VFIO MEDIATED DEVICE DRIVERS