linux-kernel - Re: [PATCH v2] x86/Kconfig: Rename UMIP config parameter

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Date:   Mon, 4 Nov 2019 13:48:51 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     "Moger, Babu" <Babu.Moger@....com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>,
        "yamada.masahiro@...ionext.com" <yamada.masahiro@...ionext.com>,
        "nayna@...ux.ibm.com" <nayna@...ux.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v2] x86/Kconfig: Rename UMIP config parameter

On Mon, Nov 04, 2019 at 08:50:51PM +0000, Moger, Babu wrote:
> AMD 2nd generation EPYC processors support the UMIP (User-Mode
> Instruction Prevention) feature. So, rename X86_INTEL_UMIP to
> generic X86_UMIP and modify the text to cover both Intel and AMD.

There's a similar comment in the umip.c documentation that needs to be
updated, and a grammatical error that can be opportunistically fixed, i.e.

 * The feature User-Mode Instruction Prevention present in recent Intel
 * processor

to 

 * The feature User-Mode Instruction Prevention present in recent x86
 * processors


IMO, the whole opening paragraph of the umip.c docs is weirdly worded and
could be rewritten to something similar to the Kconfig help text, e.g.

 * User-Mode Instruction Prevention is a security feature present in recent x86
 * processors that, when enabled, prevents a group of instructions (SGDT, SIDT,
 * SLDT, SMSW and STR) from being run in user mode by issuing a general
 * protection fault if the instruction is executed with CPL > 0.

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v2:
>   Learned that for the hardware that support UMIP, we dont need to
>   emulate. Removed the emulation related code and just submitting
>   the config changes.
> 
>  arch/x86/Kconfig                         |    8 ++++----
>  arch/x86/include/asm/disabled-features.h |    2 +-
>  arch/x86/include/asm/umip.h              |    4 ++--
>  arch/x86/kernel/Makefile                 |    2 +-
>  4 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index d6e1faa28c58..821b7cebff31 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1880,13 +1880,13 @@ config X86_SMAP
>  
>  	  If unsure, say Y.
>  
> -config X86_INTEL_UMIP
> +config X86_UMIP
>  	def_bool y
> -	depends on CPU_SUP_INTEL
> -	prompt "Intel User Mode Instruction Prevention" if EXPERT
> +	depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
> +	prompt "User Mode Instruction Prevention" if EXPERT
>  	---help---
>  	  The User Mode Instruction Prevention (UMIP) is a security

Maybe opportunistically drop "The"?

> -	  feature in newer Intel processors. If enabled, a general
> +	  feature in newer x86 processors. If enabled, a general
>  	  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.
> diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
> index a5ea841cc6d2..8e1d0bb46361 100644
> --- a/arch/x86/include/asm/disabled-features.h
> +++ b/arch/x86/include/asm/disabled-features.h
> @@ -22,7 +22,7 @@
>  # define DISABLE_SMAP	(1<<(X86_FEATURE_SMAP & 31))
>  #endif
>  
> -#ifdef CONFIG_X86_INTEL_UMIP
> +#ifdef CONFIG_X86_UMIP
>  # define DISABLE_UMIP	0
>  #else
>  # define DISABLE_UMIP	(1<<(X86_FEATURE_UMIP & 31))
> diff --git a/arch/x86/include/asm/umip.h b/arch/x86/include/asm/umip.h
> index db43f2a0d92c..aeed98c3c9e1 100644
> --- a/arch/x86/include/asm/umip.h
> +++ b/arch/x86/include/asm/umip.h
> @@ -4,9 +4,9 @@
>  #include <linux/types.h>
>  #include <asm/ptrace.h>
>  
> -#ifdef CONFIG_X86_INTEL_UMIP
> +#ifdef CONFIG_X86_UMIP
>  bool fixup_umip_exception(struct pt_regs *regs);
>  #else
>  static inline bool fixup_umip_exception(struct pt_regs *regs) { return false; }
> -#endif  /* CONFIG_X86_INTEL_UMIP */
> +#endif  /* CONFIG_X86_UMIP */
>  #endif  /* _ASM_X86_UMIP_H */
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 3578ad248bc9..52ce1e239525 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -134,7 +134,7 @@ obj-$(CONFIG_EFI)			+= sysfb_efi.o
>  obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
>  obj-$(CONFIG_TRACING)			+= tracepoint.o
>  obj-$(CONFIG_SCHED_MC_PRIO)		+= itmt.o
> -obj-$(CONFIG_X86_INTEL_UMIP)		+= umip.o
> +obj-$(CONFIG_X86_UMIP)			+= umip.o
>  
>  obj-$(CONFIG_UNWINDER_ORC)		+= unwind_orc.o
>  obj-$(CONFIG_UNWINDER_FRAME_POINTER)	+= unwind_frame.o
>