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

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
...@@ -1004,7 +1004,7 @@ config X86_THERMAL_VECTOR ...@@ -1004,7 +1004,7 @@ config X86_THERMAL_VECTOR
depends on X86_MCE_INTEL depends on X86_MCE_INTEL
config X86_LEGACY_VM86 config X86_LEGACY_VM86
bool "Legacy VM86 support (obsolete)" bool "Legacy VM86 support"
default n default n
depends on X86_32 depends on X86_32
---help--- ---help---
...@@ -1016,19 +1016,20 @@ config X86_LEGACY_VM86 ...@@ -1016,19 +1016,20 @@ config X86_LEGACY_VM86
available to accelerate real mode DOS programs. However, any available to accelerate real mode DOS programs. However, any
recent version of DOSEMU, X, or vbetool should be fully recent version of DOSEMU, X, or vbetool should be fully
functional even without kernel VM86 support, as they will all 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 Note that any app that works on a 64-bit kernel is unlikely to
this option, as 64-bit kernels don't, and can't, support V8086 need this option, as 64-bit kernels don't, and can't, support
mode. This option is also unrelated to 16-bit protected mode V8086 mode. This option is also unrelated to 16-bit protected
and is not needed to run most 16-bit programs under Wine. mode and is not needed to run most 16-bit programs under Wine.
Enabling this option adds considerable attack surface to the Enabling this option increases the complexity of the kernel
kernel and slows down system calls and exception handling. and slows down exception handling a tiny bit.
Unless you use very old userspace or need the last drop of If unsure, say N here.
performance in your real mode DOS games and can't use KVM,
say N here.
config VM86 config VM86
bool bool
......
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