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

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Message-ID: <Y4YF6KmQMys+w2hi@nvidia.com>
Date:   Tue, 29 Nov 2022 09:15:20 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     liulongfang <liulongfang@...wei.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 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?

debugfs is not a heavy burden to implement files for.

Jason