linux-kernel - Re: [PATCH] riscv: Ensure isa-ext static keys are writable

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Message-ID: <bef1a711-506a-d07b-dbd6-3a0c5f90aef2@microchip.com>
Date:   Tue, 16 Aug 2022 16:36:55 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <ajones@...tanamicro.com>, <linux-riscv@...ts.infradead.org>,
        <kvm-riscv@...ts.infradead.org>
CC:     <linux-kernel@...r.kernel.org>, <daolu@...osinc.com>,
        <jszhang@...nel.org>, <palmer@...belt.com>,
        <Conor.Dooley@...rochip.com>, <re@...z.net>,
        <apatel@...tanamicro.com>
Subject: Re: [PATCH] riscv: Ensure isa-ext static keys are writable

On 16/08/2022 17:30, Andrew Jones wrote:
> riscv_isa_ext_keys[] is an array of static keys used in the unified
> ISA extension framework. The keys added to this array may be used
> anywhere, including in modules. Ensure the keys remain writable by
> placing them in the data section.
> 
> The need to change riscv_isa_ext_keys[]'s section was found when the
> kvm module started failing to load. Commit 8eb060e10185 ("arch/riscv:
> add Zihintpause support") adds a static branch check for a newly
> added isa-ext key to cpu_relax(), which kvm uses.
> 
> Fixes: c360cbec3511 ("riscv: introduce unified static key mechanism for ISA extensions")

Hey Drew,
How about adding:

Reported-by: Ron Economos <re@...z.net>
Reported-by: Anup Patel <apatel@...tanamicro.com>
Reported-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

> Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
> ---
>  arch/riscv/kernel/cpufeature.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 553d755483ed..3b5583db9d80 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -28,7 +28,7 @@ unsigned long elf_hwcap __read_mostly;
>  /* Host ISA bitmap */
>  static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
>  
> -__ro_after_init DEFINE_STATIC_KEY_ARRAY_FALSE(riscv_isa_ext_keys, RISCV_ISA_EXT_KEY_MAX);
> +DEFINE_STATIC_KEY_ARRAY_FALSE(riscv_isa_ext_keys, RISCV_ISA_EXT_KEY_MAX);
>  EXPORT_SYMBOL(riscv_isa_ext_keys);
>  
>  /**