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From: Guo Ren <guoren@kernel.org>
To: Jessica Clarke <jrtc27@jrtc27.com>
Cc: Andy Chiu <andy.chiu@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	rostedt@goodmis.org,  Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	jpoimboe@kernel.org,  jbaron@akamai.com, ardb@kernel.org,
	greentime.hu@sifive.com,  zong.li@sifive.com, kernel@esmil.dk,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH RFC v2 riscv/for-next 5/5] riscv: align arch_static_branch function
Date: Thu, 15 Sep 2022 09:47:11 +0800	[thread overview]
Message-ID: <CAJF2gTRc487qEme5tQw4ich5xuf8_DYhTB8fp=TXav3Gs4KWnQ@mail.gmail.com> (raw)
In-Reply-To: <82E75CB4-3849-455E-807F-A0DBCAEED3CE@jrtc27.com>

On Wed, Sep 14, 2022 at 10:24 PM Jessica Clarke <jrtc27@jrtc27.com> wrote:
>
> On 13 Sept 2022, at 10:42, Andy Chiu <andy.chiu@sifive.com> wrote:
> >
> > runtime code patching must be done at a naturally aligned address, or we
> > may execute on a partial instruction.
> >
> > Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> > Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
> > ---
> > arch/riscv/include/asm/jump_label.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
> > index 38af2ec7b9bf..729991e8f782 100644
> > --- a/arch/riscv/include/asm/jump_label.h
> > +++ b/arch/riscv/include/asm/jump_label.h
> > @@ -18,6 +18,7 @@ static __always_inline bool arch_static_branch(struct static_key *key,
> >                                              bool branch)
> > {
> >       asm_volatile_goto(
> > +             "       .align          2                       \n\t"
>
> .align is a horrible directive whose meaning changes between
> architectures and requires careful thought, especially when the
> argument is a power of 2. Better to use .balign 4, or .p2align 2 if you
> really want to for some reason.
Do we really need to align here? Should it be naturally done by the compiler?

>
> Jess
>
> >               "       .option push                            \n\t"
> >               "       .option norelax                         \n\t"
> >               "       .option norvc                           \n\t"
> > @@ -39,6 +40,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key,
> >                                                   bool branch)
> > {
> >       asm_volatile_goto(
> > +             "       .align          2                       \n\t"
> >               "       .option push                            \n\t"
> >               "       .option norelax                         \n\t"
> >               "       .option norvc                           \n\t"
> > --
> > 2.36.0
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>


-- 
Best Regards
 Guo Ren

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  reply	other threads:[~2022-09-15  1:47 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-13  9:42 [PATCH RFC v2 riscv/for-next 0/5] Enable ftrace with kernel preemption for RISC-V Andy Chiu
2022-09-13  9:42 ` [PATCH RFC v2 riscv/for-next 1/5] riscv: align ftrace to 4 Byte boundary and increase ftrace prologue size Andy Chiu
2022-09-15 13:53   ` Guo Ren
2022-09-17  1:15     ` Andy Chiu
2022-09-13  9:42 ` [PATCH RFC v2 riscv/for-next 2/5] riscv: export patch_insn_write Andy Chiu
2022-09-13  9:42 ` [PATCH RFC v2 riscv/for-next 3/5] riscv: ftrace: use indirect jump to work with kernel preemption Andy Chiu
2022-09-14 13:45   ` Guo Ren
2022-09-15 13:30     ` Guo Ren
2022-09-17  1:04     ` Andy Chiu
2022-09-17 10:56       ` Guo Ren
2024-02-20 14:17   ` Evgenii Shatokhin
2022-09-13  9:42 ` [PATCH RFC v2 riscv/for-next 4/5] riscv: ftrace: do not use stop_machine to update code Andy Chiu
2022-09-13  9:42 ` [PATCH RFC v2 riscv/for-next 5/5] riscv: align arch_static_branch function Andy Chiu
2022-09-14 14:06   ` Guo Ren
2022-09-16 23:54     ` Andy Chiu
2022-09-17  0:22       ` Guo Ren
2022-09-17 18:17         ` [PATCH] riscv: jump_label: Optimize size with RISCV_ISA_C guoren
2022-09-17 18:38         ` [PATCH RFC v2 riscv/for-next 5/5] riscv: align arch_static_branch function guoren
2022-09-17 23:49           ` Guo Ren
2022-09-17 23:59           ` Guo Ren
2022-09-18  0:12           ` Jessica Clarke
2022-09-18  0:46             ` Guo Ren
2022-09-14 14:24   ` Jessica Clarke
2022-09-15  1:47     ` Guo Ren [this message]
2022-09-15  2:34       ` Jessica Clarke
2024-02-13 19:42 ` [PATCH RFC v2 riscv/for-next 0/5] Enable ftrace with kernel preemption for RISC-V Evgenii Shatokhin
2024-02-21  5:27   ` Andy Chiu
2024-02-21 16:55     ` Evgenii Shatokhin
2024-03-06 20:57       ` Alexandre Ghiti
2024-03-07  8:35         ` Evgenii Shatokhin
2024-03-07 12:27         ` Andy Chiu
2024-03-07 13:21           ` Alexandre Ghiti
2024-03-07 15:57             ` Samuel Holland
2024-03-11 14:24               ` Andy Chiu
2024-03-19 14:50                 ` Alexandre Ghiti
2024-03-19 14:58                   ` Conor Dooley
2024-03-20 16:37                   ` Andy Chiu
2024-03-18 15:31       ` Andy Chiu
2024-03-19 15:32         ` Evgenii Shatokhin
2024-03-20 16:38           ` Andy Chiu
2024-03-19 17:37         ` Alexandre Ghiti
2024-03-20 16:36           ` Andy Chiu
2024-03-21 11:02             ` Alexandre Ghiti

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