Re: userspace pci config space accesses

[Greg KH <greg@kroah.com>]

On Wed, Apr 28, 2004 at 07:38:10PM -0500, Brian King wrote:
> Greg KH wrote:
> >>>What driver is doing this?
> >>
> >>The ipr driver, a scsi device driver for ppc64.
> >>
> >>http://marc.theaimsgroup.com/?l=linux-scsi&m=108144942527994&w=2
> >>
> >>The driver runs BIST at device initialization time to ensure that the 
> >>device
> >>is in a clean state.
> >
> >
> >Ick.  It sounds like "clean state" isn't always true if userspace can
> >mess the device up by simply reading its config space :)
> 
> Yeah, its not so much the device, bus the way pSeries PCI bridges work. 
> Other adapters would have the same problem, but after a quick grep it 
> doesn't look like running BIST is a very common thing to do in most 
> Linux drivers.

Not really.

> >Worse case thing, stop the whole machine while doing BIST if you want to
> >prevent this from happening (not that I'm actually suggesting you do it,
> >but if you really think it's the only way...)
> 
> Yeah, mdelay(2000) kind of sticks out in a code review;)

And, as pointed out by others, will not work :)

> Two ideas I had would either be to create interfaces in the pci layer 
> that a device driver could call to disable all pci adapter accesses and 
> one to re-enable them. We could probably just make all pci accesses fail 
> when disabled. These interfaces could then grab the lock and set the 
> state on the pci_dev, then the read/write interfaces would check the 
> state after acquiring the lock.

Ick, we currently don't keep track of the mapping of things to do this
very easily.

I don't know what to suggest.

Good luck,

greg k-h