Re: More E820 brokenness

From: H. Peter Anvin
Date: Thu Sep 27 2007 - 20:12:40 EST


Jordan Crouse wrote:
>
> Worked, but that just raises more questions. Why didn't more x86 boxes
> break or, alternatively, why did a new version of the BIOS fix the problem?
> I guess we shouldn't look a gift horse in the mouth. Or something.
>

Why didn't more x86 boxes break... well, it's pretty natural an
implementation of the BIOS to not clobber registers that aren't outputs.
Arguably the BIOSes that do are still buggy, since there isn't a
well-defined calling sequence for the BIOS and the convention that has
evolved is "don't clobber anything unless it's an output."

It's still wrong, however, especially since it means omitting the *real*
SMAP check.

-hpa
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