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Date: Thu, 14 Sep 2017 12:26:27 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
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        Matthias Kaehlcke <mka@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH 3/4] x86/asm: Make alternative macro interfaces more
 clear and consistent
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On Thu, Sep 14, 2017 at 10:16:08AM -0700, Linus Torvalds wrote:
> On Thu, Sep 14, 2017 at 7:48 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > As it turns out, the real problem with this option is that it imposes a
> > penalty for CONFIG_FRAME_POINTER=n: even with frame pointers disabled,
> > it forces the frame pointer to be saved for each function which uses the
> > inline asm "call" statements.  Our current solution doesn't do that.
> 
> But couldn't we make the whole stack pointer clobber be dependent on
> CONFIG_FRAME_POINTER?
> 
> The only reason we do it is to make sure the frame pointer is set up
> before the inline asm is emitted, but with frame pointers disabled we
> don't need to.

We could, but then that would mean either:

 a) uglifying the 15 or so relevant inline asm locations with ifdefs; or

 b) using my ASM_CALL macro, which I think you frowned upon?

-- 
Josh