linux-kernel - Re: [PATCH] x86/kconfig/32: Mark CONFIG

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Message-ID: <20150708191333.GA26746@gmail.com>
Date:	Wed, 8 Jul 2015 21:13:33 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/kconfig/32: Mark CONFIG_VM86 as BROKEN


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Tue, Jul 7, 2015 at 7:33 PM, Arjan van de Ven <arjan@...ux.intel.com> wrote:
> >
> > if this patch would not be acceptable, at minimum we need some sort of "off by 
> > default unless the sysadmin flips a sysfs thing", which is really just a huge 
> > hack.
> 
> The only thing that matters is whether people use this or not.
> 
> If people use vm86 mode, we can't just disable it. It's that simple. "It's 
> poorly maintained" isn't an argument for removal. Only "nobody cares" works as 
> an argument for that.
> 
> My suspicion is that people still do use vm86 mode, but who knows.. Quite 
> frankly, rather than disable it, I'd much rather see people who modify low-level 
> x86 code (yes, that means you, Luto) *test* it. If you aren't willign to test 
> the modifications you make, I don't think those modifications should be merged, 
> regardless of how nice a cleanup they are.

The dosemu case might just work due to emulation (assuming emulation is equivalent 
or better than vm86 mode), but if Xorg still uses vm86 on old systems to run the 
Video-BIOS, with no fallback code available, then I doubt we can remove it.

In any case it's a lot less clear-cut than I initially thought, so I've removed 
the patch until it's determined whether it's still used by anything.

Thanks,

	Ingo
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