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Commit 1e642812 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/vm86: Fix the misleading CONFIG_VM86 Kconfig help text 



The CONFIG_VM86 Kconfig help text is actively misleading, so fix it:

  - Don't mark it 'obsolete' in the text as we'll support the ABI as long as CPUs
    support it.

  - Qualify the part about software emulation and mention that for some apps you
    want a real vm86 mode.

  - Don't scare users away from the option, instead explain what it does.

Reported-by: default avatarStas Sergeev <stsp@list.ru>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7c5b190e

arch/x86/Kconfig

+12 −11
Original line number Diff line number Diff line
@@ -1004,7 +1004,7 @@ config X86_THERMAL_VECTOR 
	depends on X86_MCE_INTEL



config X86_LEGACY_VM86

	bool "Legacy VM86 support (obsolete)"

	bool "Legacy VM86 support"

	default n

	depends on X86_32

	---help---
@@ -1016,19 +1016,20 @@ config X86_LEGACY_VM86 
	  available to accelerate real mode DOS programs.  However, any

	  recent version of DOSEMU, X, or vbetool should be fully

	  functional even without kernel VM86 support, as they will all

	  fall back to (pretty well performing) software emulation.

	  fall back to software emulation. Nevertheless, if you are using

	  a 16-bit DOS program where 16-bit performance matters, vm86

	  mode might be faster than emulation and you might want to

	  enable this option.



	  Anything that works on a 64-bit kernel is unlikely to need

	  this option, as 64-bit kernels don't, and can't, support V8086

	  mode.  This option is also unrelated to 16-bit protected mode

	  and is not needed to run most 16-bit programs under Wine.

	  Note that any app that works on a 64-bit kernel is unlikely to

	  need this option, as 64-bit kernels don't, and can't, support

	  V8086 mode. This option is also unrelated to 16-bit protected

	  mode and is not needed to run most 16-bit programs under Wine.



	  Enabling this option adds considerable attack surface to the

	  kernel and slows down system calls and exception handling.

	  Enabling this option increases the complexity of the kernel

	  and slows down exception handling a tiny bit.



	  Unless you use very old userspace or need the last drop of

	  performance in your real mode DOS games and can't use KVM,

	  say N here.

	  If unsure, say N here.



config VM86

       bool