linux-kernel - Re: [PATCH v3 3/5] LoongArch: BPF: Add EXECMEM

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Message-ID: <CAAhV-H6bKrnDpVouriAoMUN5i26G6a+UuOGMyEj5h9kJGd6qnQ@mail.gmail.com>
Date: Wed, 9 Jul 2025 23:23:12 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Chenghao Duan <duanchenghao@...inos.cn>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	yangtiezhu@...ngson.cn, hengqi.chen@...il.com, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, kernel@...0n.name, 
	linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev, bpf@...r.kernel.org, 
	guodongtai@...inos.cn, youling.tang@...ux.dev, jianghaoran@...inos.cn
Subject: Re: [PATCH v3 3/5] LoongArch: BPF: Add EXECMEM_BPF memory to execmem subsystem

Hi, Chenghao,

On Wed, Jul 9, 2025 at 1:50 PM Chenghao Duan <duanchenghao@...inos.cn> wrote:
>
> The bpf_jit_alloc_exec function serves as the core mechanism for BPF
> memory allocation, invoking execmem_alloc(EXECMEM_BPF, size) to
> allocate memory. This change explicitly designates the allocation space
> for EXECMEM_BPF.
Without this patch, BPF JIT is allocated from MODULES region; with
this patch, BPF JIT will be allocated from VMALLOC region. However,
BPF JIT is similar to modules that the target of direct branch
instruction is limited, so it should also be allocated from the
MODULES region.

So, it is better to drop this patch.


Huacai

>
> Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
> ---
>  arch/loongarch/mm/init.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index c3e4586a7..07cedd9ee 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -239,6 +239,12 @@ struct execmem_info __init *execmem_arch_setup(void)
>                                 .pgprot = PAGE_KERNEL,
>                                 .alignment = 1,
>                         },
> +                       [EXECMEM_BPF] = {
> +                               .start  = VMALLOC_START,
> +                               .end    = VMALLOC_END,
> +                               .pgprot = PAGE_KERNEL,
> +                               .alignment = PAGE_SIZE,
> +                       },
>                 },
>         };
>
> --
> 2.43.0
>
>