linux-kernel - Re: [PATCH v3 1/5] vfio/migration: Add debugfs to live migration driver

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Date:   Thu, 1 Dec 2022 09:37:02 +0800
From:   liulongfang <liulongfang@...wei.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     <alex.williamson@...hat.com>,
        <shameerali.kolothum.thodi@...wei.com>, <john.garry@...wei.com>,
        <cohuck@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...neuler.org>
Subject: Re: [PATCH v3 1/5] vfio/migration: Add debugfs to live migration
 driver

On 2022/11/29 21:15, Jason Gunthorpe wrote:
> On Tue, Nov 29, 2022 at 10:02:46AM +0800, liulongfang wrote:
>> On 2022/11/28 21:39, Jason Gunthorpe wrote:
>>> On Mon, Nov 28, 2022 at 11:11:56AM +0800, Longfang Liu wrote:
>>>
>>>> @@ -119,6 +132,9 @@ 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);
>>>> +	int (*migration_debug_operate)(struct vfio_device *device,
>>>>  				   unsigned int cmd);
>>>
>>> Please don't do wrappers like this, give the variant driver a chance
>>> to create its own files natively under the debugfs directory
>>>
>>
>> Using this public debugfs file does not need to deal with file
>> creation and destruction.
>> The driver only needs to define its debug operation command,
>> isn't it simpler?
> 
> No, it is obfuscating the normal kernel apis, what if a driver wants
> two files?
> 

Yes, if there are special devices that require multiple debugfs files
and use the same operation, using this migration_debug_operate() will
cause the function to be impossible.

Thanks,
Longfang.

> debugfs is not a heavy burden to implement files for.
>
> Jason
> .
>