netdev - Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free

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Message-ID: <mhng-3299fb62-01d1-4e83-90fe-d706d2495bc1@palmerdabbelt-glaptop>
Date:   Mon, 23 Dec 2019 10:30:38 -0800 (PST)
From:   Palmer Dabbelt <palmerdabbelt@...gle.com>
To:     Bjorn Topel <bjorn.topel@...il.com>
CC:     daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org,
        Bjorn Topel <bjorn.topel@...il.com>,
        linux-riscv@...ts.infradead.org, bpf@...r.kernel.org
Subject:     Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free

On Mon, 16 Dec 2019 01:13:40 PST (-0800), Bjorn Topel wrote:
> This commit makes sure that the JIT images is kept close to the kernel
> text, so BPF calls can use relative calling with auipc/jalr or jal
> instead of loading the full 64-bit address and jalr.
>
> The BPF JIT image region is 128 MB before the kernel text.
>
> Signed-off-by: Björn Töpel <bjorn.topel@...il.com>
> ---
>  arch/riscv/include/asm/pgtable.h |  4 ++++
>  arch/riscv/net/bpf_jit_comp.c    | 13 +++++++++++++
>  2 files changed, 17 insertions(+)
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 7ff0ed4f292e..cc3f49415620 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -404,6 +404,10 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>  #define VMALLOC_END      (PAGE_OFFSET - 1)
>  #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
>
> +#define BPF_JIT_REGION_SIZE	(SZ_128M)
> +#define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
> +#define BPF_JIT_REGION_END	(VMALLOC_END)
> +
>  /*
>   * Roughly size the vmemmap space to be large enough to fit enough
>   * struct pages to map half the virtual address space. Then
> diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
> index 8aa19c846881..46cff093f526 100644
> --- a/arch/riscv/net/bpf_jit_comp.c
> +++ b/arch/riscv/net/bpf_jit_comp.c
> @@ -1656,3 +1656,16 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>  					   tmp : orig_prog);
>  	return prog;
>  }
> +
> +void *bpf_jit_alloc_exec(unsigned long size)
> +{
> +	return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START,
> +				    BPF_JIT_REGION_END, GFP_KERNEL,
> +				    PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
> +				    __builtin_return_address(0));
> +}
> +
> +void bpf_jit_free_exec(void *addr)
> +{
> +	return vfree(addr);
> +}

Ah, I guess I should have read the whole patch set :)

Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>

and feel free to put the same on whatever patch I just asked that question
on, though maybe this one should go before the others as they sort of depend on
it?