Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

Andi Kleen
2007-12-08T00:21:37Z

On Wed, Dec 05, 2007 at 11:10:39AM +0000, Pavel Machek wrote:
> On Fri 2007-12-07 09:50:26, David P. Reed wrote:
> > My machine in question, for example, needs no waiting
> > within CMOS_READs at all. And I doubt any other
> > chip/device needs waiting that isn't already provided by
> > the bus. the i/o to port 80 is very, very odd in this
> > context. Actually, modern machines have potentially
> > more serious problems with i/o ops to non-existent
> > addresses, which may cause real bus wierdness.
>
> I dislike outb_p clobbering port 0x80, but you are wrong here. BIOSes
> already do outs to port 0x80 for debugging reason, so these accesses
> are unlikely to do something bad.

They only do that briefly during boot though. But Linux
can do it much more often. If it's a race
or similar it might just not trigger with the BIOS.

-Andi