ATI rage xl.init
rminnich at lanl.gov
Mon Apr 26 09:07:01 CEST 2004
On Mon, 26 Apr 2004, Stefan Reinauer wrote:
> > Devices with bus master set are allowed to DMA into main memory
> > whenever they feel like it so it is dangerous to enable that
> > bit indiscriminately.
> --> If at all, it should be done with careful checking.
Here is a possible scenario. You are in linuxbios after somehow falling
into it -- i.e., no power up, no reset has happened. Devices for whatever
reason are not totally reset, including the ethernet device. The ethernet
device is the kind with on-chip buffer queue pointerss. You enable bus
master. Chip gets a broadcast packet. It writes it somewhere to memory,
over code that won't get run in 2 or 3 weeks. 2 or 3 weeks later, the code
Your kernel goes kaboom!
How do you figure out what happened? This is a possible scenario that can
happen once you start enabling bus master in the bios.
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