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x86/umip: Select X86_INTEL_UMIP by default

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UMIP does cause any performance penalty to the vast majority of x86 code
that does not use the legacy instructions affected by UMIP.

Also describe UMIP more accurately and explain the behavior that can be
expected by the (few) applications that use the affected instructions.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: ricardo.neri@intel.com
Link: http://lkml.kernel.org/r/1510640985-18412-2-git-send-email-ricardo.neri-calderon@linux.intel.com
[ Spelling fixes, rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ricardo Neri 2017-11-13 22:29:42 -08:00 committed by Ingo Molnar
parent b29c6ef7bb
commit 796ebc81b9
1 changed files with 9 additions and 3 deletions
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12
arch/x86/Kconfig
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@ -1805,14 +1805,20 @@ config X86_SMAP
If unsure, say Y.
config X86_INTEL_UMIP
def_bool n
def_bool y
depends on CPU_SUP_INTEL
prompt "Intel User Mode Instruction Prevention" if EXPERT
---help---
The User Mode Instruction Prevention (UMIP) is a security
feature in newer Intel processors. If enabled, a general
protection fault is issued if the instructions SGDT, SLDT,
SIDT, SMSW and STR are executed in user mode.
protection fault is issued if the SGDT, SLDT, SIDT, SMSW
or STR instructions are executed in user mode. These instructions
unnecessarily expose information about the hardware state.
The vast majority of applications do not use these instructions.
For the very few that do, software emulation is provided in
specific cases in protected and virtual-8086 modes. Emulated
results are dummy.
config X86_INTEL_MPX
prompt "Intel MPX (Memory Protection Extensions)"