RE: [PATCH v2] x86/Kconfig: Rename UMIP config parameter

[Moger, Babu]

> -----Original Message-----
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Sent: Monday, November 4, 2019 3:49 PM
> To: Moger, Babu <Babu.Moger@xxxxxxx>
> Cc: tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; bp@xxxxxxxxx; hpa@xxxxxxxxx;
> pbonzini@xxxxxxxxxx; rkrcmar@xxxxxxxxxx; vkuznets@xxxxxxxxxx;
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> kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx
> 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
> 
Sure.
> 
> 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.

Sure. Will update it. Will add as patch #2 as this is separate from config file.

> 
> >
> > Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> > ---
> > 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"?
Sure.
> 
> > -	  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
> >