Wow! A hole in linuxbios PCI mastery setup?

[Eric W. Biederman]

"Ronald G. Minnich" <rminnich at lanl.gov> writes:

> we don't turn on bus master as that could be very hazardous to your health 
> -- imagine an unitialized PCI device coming up with bus master enabled. It 
> is at that point allowed to do DMA cycles to RAM without having been 
> initialized by a driver. OUCH. 
> 
> In my opinion if the driver is not turning on bus master it is a buggy 
> driver. If the device comes up with bus master enabled it is a buggy 
> device. Ollie has pointed this out too. There's a lot of buggy PCI 
> hardware in existence. 
> 
> I think the Award BIOS is buggy, possibly intentionally, to deal with 
> buggy drivers (there are lots of BIOS patches that are in there, I am 
> told, to fix buggy device drivers in Windows). 

I am not totally certain that it is buggy.  There are places this
can be reasonable behavior.  Experience with etherboot shows that
normally boot devices at least have bus master set by the BIOS.
Though not often enough to do something reasonable with it.
 
> I would recommend fixing the 802.11 driver, rather than modifying 
> LinuxBIOS. But let's see what other people say.

Agreed.  Not all BIOSes enable bus mastering on all networking hardware.
So changing the LinuxBIOS behavior will not necessarily help.

Eric