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

[Alexander Graf <agraf@suse.de>]

Daniel P. Berrange wrote:
> On Wed, Dec 09, 2009 at 08:18:21PM +0100, Alexander Graf wrote:
>   
>> Daniel P. Berrange wrote:
>>     
>>> 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.
>>>   
>>>       
>> Oh - mind to get into detail there? It'd be great if we could tell users
>> an even better way to unbind their device from the driver than rmmod :)
>>     
>
> The direct low level sysfs way involves the following steps
>
>   // Tell pci-stub to accept a particular vendor+product ID binding
>   # echo "8086 27cb" > /sys/bus/pci/drivers/pci-stub/new_id
>
>   // Remove device from existing PCI driver
>   # echo "00:1d.3" > /sys/bus/pci/drivers/e1000/unbind
>
>   // Add device to pci-stub PCI driver
>   # echo "00:1d.3" > /sys/bus/pci/drivers/pci-stub/bind
>
>   // Tell pci-stub to stop accepting a vendor+product ID binding
>   # echo "8086 27cb" > /sys/bus/pci/drivers/pci-stub/remove_id
>
> The reason for  that last step is that if you have multiple devices of
> the same vendor+product, you don't want a later hotplug event to bind
> the new device to pci-stub too !
>   

So what would you think if we'd just print out those 4 commands to the
user, so people who don't use libvirt still get guidance when using
-pcidevice :). They should be fairly easy to construct from the
information we have.

Alex