Commit-ID: 796ebc81b9931bfa293b4ca38ae28c21a363f4d0 Gitweb: https://git.kernel.org/tip/796ebc81b9931bfa293b4ca38ae28c21a363f4d0 Author: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> AuthorDate: Mon, 13 Nov 2017 22:29:42 -0800 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 14 Nov 2017 08:38:08 +0100 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 <mingo@xxxxxxxxxx> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Ravi V. Shankar <ravi.v.shankar@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: ricardo.neri@xxxxxxxxx Link: http://lkml.kernel.org/r/1510640985-18412-2-git-send-email-ricardo.neri-calderon@xxxxxxxxxxxxxxx [ Spelling fixes, rewrote the changelog. ] Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/Kconfig | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f08977d..a0623f0 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 ---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)" -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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