linux-kernel - Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush

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Message-ID: <56cc1e25-25c3-a3da-64e3-8a1c539d685b@iogearbox.net>
Date:   Tue, 1 Jun 2021 19:20:04 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Yanfei Xu <yanfei.xu@...driver.com>, ast@...nel.org,
        zlim.lnx@...il.com, catalin.marinas@....com, will@...nel.org,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush_icache

On 6/1/21 5:06 PM, Yanfei Xu wrote:
> It's no need to trigger IPI for keeping pipeline fresh in bpf case.

This needs a more concrete explanation/analysis on "why it is safe" to do so
rather than just saying that it is not needed.

> Signed-off-by: Yanfei Xu <yanfei.xu@...driver.com>
> ---
>   arch/arm64/net/bpf_jit_comp.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index f7b194878a99..5311f8be4ba4 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -974,7 +974,7 @@ static int validate_code(struct jit_ctx *ctx)
>   
>   static inline void bpf_flush_icache(void *start, void *end)
>   {
> -	flush_icache_range((unsigned long)start, (unsigned long)end);
> +	__flush_icache_range((unsigned long)start, (unsigned long)end);
>   }
>   
>   struct arm64_jit_data {
>