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

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Date:	Fri, 10 Jul 2015 10:39:02 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	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

On Fri, Jul 10, 2015 at 10:13 AM, Andy Lutomirski <luto@...capital.net> wrote:
>
> The problem is that it's *every* event.  That includes this that
> happen literally every time like strace.  (NOHZ_FULL would count, too,
> if it worked at all on 32-bit kernels.)

But things like strace and auditing etc has probably never worked in
the first place.

So yeah, I can well imagine that vm86 isn't universally useful. And
maybe it's been effectively broken in halfway modern distributions due
to their insane use of auditing - which is wonderful, because it's
just a stronger argument for disabling it by default.

But what I'd worry about is regressions - people who actually want to
upgrade kernels, and had an old machine and had an old distro, and
just want to keep that working. They aren't interested in running
strace on their old DOS game, or on their X server that uses it to run
the video BIOS. They just want it to work.

And it doesn't look "completely broken" to me for that.

Put another way: I think vm86 is very much "legacy". Nobody cares
about it in modern environments. That's not what we should even worry
about. We shouldn't worry about new users, and we _should_ try to
discourage it. But I think we should keep it working for the cases it
used to work before.

So no marking it "BROKEN". No calling it names just because it doesn't
work in insane situations that nobody cares about. It's a legacy
thing, and it probably has very few users, but I'm getting the vibe
that you want to remove it or hate it just because it might not work
in situations that simply don't make sense in the first place, and
that it was never used for anyway.

                 Linus
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