Re: [PATCH v2 6/7] x86: Allow disabling HW_BREAKPOINTS, PERF_EVENTS, INSTRUCTION_DECODER, IRQ_WORK

[Josh Triplett <josh@joshtriplett.org>]

On Mon, Mar 10, 2014 at 05:14:11PM +0100, Frederic Weisbecker wrote:
> On Sun, Mar 09, 2014 at 08:12:53PM -0700, Josh Triplett wrote:
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -70,9 +70,6 @@ config X86
> >  	select HAVE_KERNEL_XZ
> >  	select HAVE_KERNEL_LZO
> >  	select HAVE_KERNEL_LZ4
> > -	select HAVE_HW_BREAKPOINT
> > -	select HAVE_MIXED_BREAKPOINTS_REGS
> > -	select PERF_EVENTS
> >  	select HAVE_PERF_EVENTS_NMI
> >  	select HAVE_PERF_REGS
> >  	select HAVE_PERF_USER_STACK_DUMP
> > @@ -587,6 +584,15 @@ config SCHED_OMIT_FRAME_POINTER
> >  
> >  	  If in doubt, say "Y".
> >  
> > +config HW_BREAKPOINTS
> > +	bool "Enable hardware breakpoints support" if EXPERT
> > +	default y
> > +	select HAVE_HW_BREAKPOINT
> > +	select HAVE_MIXED_BREAKPOINTS_REGS
> > +	---help---
> > +	  Enable support for x86 hardware breakpoints for debuggers
> > +	  and perf.  This will implicitly enable perf-events.
> > +
> 
> HW_BREAKPOINTS must depend on HAVE_HW_BREAKPOINT, not the other way round.
> HAVE_* Kconfig symbols must only express constant backend support, not a variable user choice...
> 
> ie, that's what I did in this patchset
> https://lkml.org/lkml/2011/7/14/163

So, the converse of that is that makefiles and code should never depend
on HAVE_* symbols; they should only be used in Kconfig as dependencies.
Right now, piles of things use HAVE_HW_BREAKPOINT to select things to
build.  So, the biggest chunk of this change is introducing a new dummy
symbol HW_BREAKPOINTS depending on HAVE_HW_BREAKPOINT and
HAVE_MIXED_BREAKPOINTS_REGS, and changing almost all the references to
HAVE_HW_BREAKPOINT to HW_BREAKPOINTS.

That's effectively patch 2/6 of your series.  Would you consider
reviving that patch, or should I pull that patch into this series
instead?

- Josh Triplett

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