Re: [tip:x86/setup] x86, setup: "glove box" BIOS calls -- infrastructure

["H. Peter Anvin" <hpa@zytor.com>]

Linus Torvalds wrote:
> 
> This discussion is just taking us down a rat-hole of more complexity, and 
> _way_ more fragility.
> 
> I'm absolutely willing to bet that trying to do the BIOS calls will break 
> way more than it will fix. Sure, it will probably work for 99.9% of all 
> BIOSes, but then it will break horribly for some BIOS that tries to do 
> something "clever". SMM has already been mentioned as an example of 
> something that simply isn't virtualizable.
> 
> Timing is another, very traditional, one. There used to be video BIOSes 
> that simply didn't work in a dosbox-like environment because they had 
> tight timing loops that were coupled to hardware. I can pretty much 
> guarantee that that has gone away as far as the video BIOS is concerned, 
> but the main BIOS? Who the hell knows.
> 
> Sure, none of the calls we do to the BIOS from the kernel should need 
> anything fancy at all, and maybe I'm pessimistic. But at the same time, I 
> really don't think the BIOS calls are worth that kind of infrastructure. 
> 
> Sure, go ahead and wrap them in some kind of "save and restore all 
> registers" wrapping, but nothing fancier than that. It would just be 
> overkill, and likely to break more than it fixes.
> 

Agreed completely.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.