Re: [PATCH] Inform users about busy device assignment attempt

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Dec 09, 2009 at 07:04:13PM +0100, Alexander Graf wrote:
> When using -pcidevice on a device that is already in use by a kernel driver
> all the user gets is the following (very useful) information:
> 
>   Failed to assign device "04:00.0" : Device or resource busy
>   Failed to deassign device "04:00.0" : Invalid argument
>   Error initializing device pci-assign
> 
> Since I usually prefer to have my computer do the thinking for me, I figured
> it might be a good idea to check and see if a device is actually used by a
> driver. If so, tell the user.
> 
> So with this patch applied you get the following output:
> 
>   Failed to assign device "04:00.0" : Device or resource busy
>   *** The driver 'igb' is occupying your device 04:00.0.
>   *** Try running "rmmod igb" on the commandline
>   Failed to deassign device "04:00.0" : Invalid argument
>   Error initializing device pci-assign
> 
> That should keep people like me from doing the most obvious misuses :-).

Unconditionally telling people to run rmmod is a pretty dangerous thing
todo. If they typod and gave the PCI addr of their disk controller instead
of the NIC, they'll be less than happy at the results of our recommended
command to "fix" the error. Likewise if they have multiple devices using
the same driver & just want to assign one of them. I think it is safer to
just have the first bit of your proposed error message

  "The device 04:00.0 is in use by the kernel driver 'igb'."


NB 'rmmod' is not the ideal approach for PCI assignment. It is better
to explicitly re-bind the device to 'pcistub' because that ensures that
no other driver will ever be able to reclaim the device.

Regards,
Daniel
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