linux-kernel - Re: [PATCH v4 00/18] Add static

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Date:   Wed, 6 May 2020 20:05:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, pbonzini@...hat.com,
        mathieu.desnoyers@...icios.com
Subject: Re: [PATCH v4 00/18] Add static_call()

On Wed, May 06, 2020 at 12:32:29PM -0500, Josh Poimboeuf wrote:
> On Fri, May 01, 2020 at 10:28:49PM +0200, Peter Zijlstra wrote:
> > static_call(), is the idea of static_branch() applied to indirect function
> > calls. Remove a data load (indirection) by modifying the text.
> > 
> > The inline implementation still relies on objtool to generate the
> > .static_call_sites section, mostly because this is a natural place for x86_64
> > and works for both GCC and LLVM.  Other architectures can pick other means
> > if/when they implement the inline patching. The out-of-line (aka. trampoline)
> > variant doesn't require this.
> > 
> > Patches go on top of tip/objtool/core.
> > 
> > Patches can also be found here:
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/static_call
> 
> So this branch has
> 
>   45a5c99a226a ("x86/tlb: Move trace_tlb_flush() declaration")
> 
> but I didn't see it posted here.  I guess you dropped it because it's no
> longer needed b/c we fixed those 'undefined references' a different way.

Correct; still prossibly a sane clean-up, but I got rid of it for now.