Re: That horrible hack from hell called A20

H. Peter Anvin
2000-12-06T01:41:24Z

Linus Torvalds wrote:
>
> Actually, I bet I know what's up.
>
> Want to bet $5 USD that suspend/resume saves the keyboard A20 state, but
> does NOT save the fast-A20 gate information?
>
> So anything that enables A20 with only the fast A20 gate will find that
> A20 is disabled again on resume.
>
> Which would make Linux _really_ unhappy, needless to say. Instant death in
> the form of a triple fault (all of the Linux kernel code is in the 1-2MB
> area, which would be invisible), resulting in an instant reboot.
>
> Peter, we definitely need to do the keyboard A20, even if fast-A20 works
> fine.
>

Yup. It's a BIOS bug, oh what a shocker... (that never happens, right)?

I might hack on using INT 15h to do the jump to protected mode, as ugly
as it is, but I won't have time before my trip. It would require quite a
bit of restructuring in setup.S, and would probably break LOADLIN.

-hpa

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."