linux-kernel - Re: [PATCH -fixes] riscv: Re-introduce global icache flush in patch_text

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Message-ID: <0719e155-0a07-4878-87e3-cd96fed7a1dd@sifive.com>
Date: Thu, 1 Aug 2024 12:32:28 -0500
From: Samuel Holland <samuel.holland@...ive.com>
To: Alexandre Ghiti <alexghiti@...osinc.com>,
 Palmer Dabbelt <palmer@...belt.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Albert Ou <aou@...s.berkeley.edu>, Andy Chiu <andy.chiu@...ive.com>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -fixes] riscv: Re-introduce global icache flush in
 patch_text_XXX()

Hi Alex,

On 2024-07-30 8:59 AM, Alexandre Ghiti wrote:
> commit edf2d546bfd6 ("riscv: patch: Flush the icache right after
> patching to avoid illegal insns") mistakenly removed the global icache
> flush in patch_text_nosync() and patch_text_set_nosync() functions, so
> reintroduce them.
> 
> Fixes: edf2d546bfd6 ("riscv: patch: Flush the icache right after patching to avoid illegal insns")
> Reported-by: Samuel Holland <samuel.holland@...ive.com>
> Closes: https://lore.kernel.org/linux-riscv/CAHVXubh8Adb4=-vN4cSh0FrZ16TeOKJbLj4AF09QC241bRk1Jg@mail.gmail.com/T/#m800757c26f72a1d45c240cb815650430166c82ea

Shouldn't this use the permalink for the specific message, not the thread?

> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> ---
>  arch/riscv/kernel/patch.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
> index ab03732d06c4..91edfd764ed9 100644
> --- a/arch/riscv/kernel/patch.c
> +++ b/arch/riscv/kernel/patch.c
> @@ -205,6 +205,9 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len)
>  
>  	ret = patch_insn_set(tp, c, len);
>  
> +	if (!ret)
> +		flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);

This patch was based on an old tree from before
https://git.kernel.org/riscv/c/47742484ee16 removed the "tp" variable. While it
still compiles because flush_icache_range() is a macro that discards its
arguments, it will be confusing to anyone reading the code.

Regards,
Samuel

> +
>  	return ret;
>  }
>  NOKPROBE_SYMBOL(patch_text_set_nosync);
> @@ -237,6 +240,9 @@ int patch_text_nosync(void *addr, const void *insns, size_t len)
>  
>  	ret = patch_insn_write(tp, insns, len);
>  
> +	if (!ret)
> +		flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
> +
>  	return ret;
>  }
>  NOKPROBE_SYMBOL(patch_text_nosync);