linux-kernel - Re: [PATCH v2 2/2] riscv: switch has_fpu() to the unified static key mechanism

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Date:   Mon, 23 May 2022 07:41:35 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Jisheng Zhang <jszhang@...nel.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] riscv: switch has_fpu() to the unified static key mechanism

On Sun, May 22, 2022 at 8:44 AM Jisheng Zhang <jszhang@...nel.org> wrote:
>
> This is to use the unified static key mechanism instead of putting
> static key related here and there.
>
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>  arch/riscv/include/asm/switch_to.h | 4 ++--
>  arch/riscv/kernel/cpufeature.c     | 7 -------
>  2 files changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
> index 0a3f4f95c555..11463489fec6 100644
> --- a/arch/riscv/include/asm/switch_to.h
> +++ b/arch/riscv/include/asm/switch_to.h
> @@ -8,6 +8,7 @@
>
>  #include <linux/jump_label.h>
>  #include <linux/sched/task_stack.h>
> +#include <asm/hwcap.h>
>  #include <asm/processor.h>
>  #include <asm/ptrace.h>
>  #include <asm/csr.h>
> @@ -56,10 +57,9 @@ static inline void __switch_to_aux(struct task_struct *prev,
>         fstate_restore(next, task_pt_regs(next));
>  }
>
> -extern struct static_key_false cpu_hwcap_fpu;
>  static __always_inline bool has_fpu(void)
>  {
> -       return static_branch_likely(&cpu_hwcap_fpu);
> +       return static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_FPU]);
>  }
>  #else
>  static __always_inline bool has_fpu(void) { return false; }
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 89f886b35357..0235391be84b 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -21,9 +21,6 @@ unsigned long elf_hwcap __read_mostly;
>  /* Host ISA bitmap */
>  static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
>
> -#ifdef CONFIG_FPU
> -__ro_after_init DEFINE_STATIC_KEY_FALSE(cpu_hwcap_fpu);
> -#endif
>  __ro_after_init DEFINE_STATIC_KEY_ARRAY_FALSE(riscv_isa_ext_keys, RISCV_ISA_EXT_KEY_MAX);
>  EXPORT_SYMBOL(riscv_isa_ext_keys);
>
> @@ -239,8 +236,4 @@ void __init riscv_fill_hwcap(void)
>                 if (j >= 0)
>                         static_branch_enable(&riscv_isa_ext_keys[j]);
>         }
> -#ifdef CONFIG_FPU
> -       if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
> -               static_branch_enable(&cpu_hwcap_fpu);
> -#endif
>  }
> --
> 2.34.1
>

Reviewed-by: Atish Patra <atishp@...osinc.com>

-- 
Regards,
Atish