linux-kernel - Re: [PATCH v2 3/3] jump_label: make initial NOP patching the special case

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Message-ID: <CAMj1kXFfVi8sYXR0z42v72XfTBaQ9jaDAzuLuK=TBKHUqKkEPA@mail.gmail.com>
Date:   Thu, 16 Jun 2022 13:25:02 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        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>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        "open list:S390" <linux-s390@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] jump_label: make initial NOP patching the special case

On Wed, 15 Jun 2022 at 17:41, Ard Biesheuvel <ardb@...nel.org> 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>
> Acked-by: Mark Rutland <mark.rutland@....com>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.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, 7 insertions(+), 83 deletions(-)
>

This needs the following hunk as well, as spotted by the bot:

--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -220,8 +220,6 @@ extern void jump_label_lock(void);
 extern void jump_label_unlock(void);
 extern void arch_jump_label_transform(struct jump_entry *entry,
                                      enum jump_label_type type);
-extern void arch_jump_label_transform_static(struct jump_entry *entry,
-                                            enum jump_label_type type);
 extern bool arch_jump_label_transform_queue(struct jump_entry *entry,
                                            enum jump_label_type type);
 extern void arch_jump_label_transform_apply(void);

Let me know if I need to resend for this.