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

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Message-ID: <20250710072337.GA839477@chenghao-pc>
Date: Thu, 10 Jul 2025 15:23:37 +0800
From: Chenghao Duan <duanchenghao@...inos.cn>
To: Huacai Chen <chenhuacai@...nel.org>
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

On Wed, Jul 09, 2025 at 11:23:12PM +0800, Huacai Chen wrote:
> 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

Dear Chen,

I understand your technical considerations. Whether to keep or remove
the current patch has no impact on trampoline, so we can drop this
patch.

Chenghao

> 
> >
> > 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
> >
> >