diff options
authorRicardo Neri <>2017-11-13 22:29:42 -0800
committerIngo Molnar <>2017-11-14 08:38:08 +0100
commit796ebc81b9931bfa293b4ca38ae28c21a363f4d0 (patch)
parentb29c6ef7bb1257853c1e31616d84f55e561cf631 (diff)
x86/umip: Select X86_INTEL_UMIP by default
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 <> Signed-off-by: Ricardo Neri <> Cc: Andy Lutomirski <> Cc: Borislav Petkov <> Cc: Linus Torvalds <> Cc: Paolo Bonzini <> Cc: Peter Zijlstra <> Cc: Ravi V. Shankar <> Cc: Thomas Gleixner <> Cc: Tony Luck <> Cc: Link: [ Spelling fixes, rewrote the changelog. ] Signed-off-by: Ingo Molnar <>
1 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f08977d82ca0..a0623f0668ab 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -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
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)"