linux-kernel - Re: [PATCH 3/3] jump_label: make initial NOP patching the special case

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Message-ID: <YqmvL2Biw3TnIl7a@hirez.programming.kicks-ass.net>
Date:   Wed, 15 Jun 2022 12:06:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-mips@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 3/3] jump_label: make initial NOP patching the special
 case

On Wed, Jun 15, 2022 at 10:52:41AM +0100, Mark Rutland wrote:
> On Wed, Jun 08, 2022 at 12:45:12PM +0200, Ard Biesheuvel wrote:
> > Instead of defaulting to patching NOP opcodes at init time, and leaving
> > it to the architectures to override this if this is not needed, switch
> > to a model where doing nothing is the default. This is the common case
> > by far, as only MIPS requires NOP patching at init time. On all other
> > architectures, the correct encodings are emitted by the compiler and so
> > no initial patching is needed.
> > 
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> > ---
> >  Documentation/staging/static-keys.rst |  3 ---
> >  arch/arc/kernel/jump_label.c          | 13 -------------
> >  arch/arm/kernel/jump_label.c          |  6 ------
> >  arch/arm64/kernel/jump_label.c        | 11 -----------
> >  arch/mips/include/asm/jump_label.h    |  2 ++
> >  arch/parisc/kernel/jump_label.c       | 11 -----------
> >  arch/riscv/kernel/jump_label.c        | 12 ------------
> >  arch/s390/kernel/jump_label.c         |  5 -----
> >  arch/x86/kernel/jump_label.c          | 13 -------------
> >  kernel/jump_label.c                   | 14 +++-----------
> >  10 files changed, 5 insertions(+), 85 deletions(-)
> 
> I have one minor comment below, but either way this is a nice cleanup (and I'm
> always happy to see __weak functions disappear), so FWIW:

(I've got a new found hatred for __weak after having had to fix so many
objtool issues with it, so yeah, that).

> 
>   Acked-by: Mark Rutland <mark.rutland@....com>

With the thing Mark pointed out fixed:

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

(although, I'll probably be the one to eventually apply these I suppose,
unless they're needed in a different tree?)