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

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Message-ID: <0edc2f30-5662-392f-77a0-bd93379df724@w6rz.net>
Date:   Tue, 16 Aug 2022 14:20:30 -0700
From:   Ron Economos <re@...z.net>
To:     Andrew Jones <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,
        Anup Patel <apatel@...tanamicro.com>
Subject: Re: [PATCH] riscv: Ensure isa-ext static keys are writable

On 8/16/22 9:30 AM, 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")
> 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);
>   
>   /**

Works good on HiFive Unmatched.

Tested-by: Ron Economos <re@...z.net>