Re: [PATCH bpf-next v2 2/2] bpf, riscv: Remove redundant bpf_flush_icache() after pack allocator finalize

[Pu Lehui <pulehui@huawei.com>]

On 2026/4/14 3:11, Puranjay Mohan wrote:
> bpf_flush_icache() calls flush_icache_range() to clean the data cache
> and invalidate the instruction cache for the JITed code region. However,
> since commit 48a8f78c50bd ("bpf, riscv: use prog pack allocator in the
> BPF JIT"), this flush is redundant.
> 
> bpf_jit_binary_pack_finalize() copies the JITed instructions to the ROX
> region via bpf_arch_text_copy() -> patch_text_nosync(), and
> patch_text_nosync() already calls flush_icache_range() on the written
> range. The subsequent bpf_flush_icache() repeats the same cache
> maintenance on an overlapping range.
> 
> Remove the redundant bpf_flush_icache() call and its now-unused
> definition.
> 
> Fixes: 48a8f78c50bd ("bpf, riscv: use prog pack allocator in the BPF JIT")
> Acked-by: Song Liu <song@kernel.org>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
>   arch/riscv/net/bpf_jit.h      | 6 ------
>   arch/riscv/net/bpf_jit_core.c | 7 -------
>   2 files changed, 13 deletions(-)
> 
> diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
> index 632ced07bca4..da0271790244 100644
> --- a/arch/riscv/net/bpf_jit.h
> +++ b/arch/riscv/net/bpf_jit.h
> @@ -11,7 +11,6 @@
>   
>   #include <linux/bpf.h>
>   #include <linux/filter.h>
> -#include <asm/cacheflush.h>
>   
>   /* verify runtime detection extension status */
>   #define rv_ext_enabled(ext) \
> @@ -105,11 +104,6 @@ static inline void bpf_fill_ill_insns(void *area, unsigned int size)
>   	memset(area, 0, size);
>   }
>   
> -static inline void bpf_flush_icache(void *start, void *end)
> -{
> -	flush_icache_range((unsigned long)start, (unsigned long)end);
> -}
> -
>   /* Emit a 4-byte riscv instruction. */
>   static inline void emit(const u32 insn, struct rv_jit_context *ctx)
>   {
> diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
> index b3581e926436..f7fd4afc3ca3 100644
> --- a/arch/riscv/net/bpf_jit_core.c
> +++ b/arch/riscv/net/bpf_jit_core.c
> @@ -183,13 +183,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>   			prog = orig_prog;
>   			goto out_offset;
>   		}
> -		/*
> -		 * The instructions have now been copied to the ROX region from
> -		 * where they will execute.
> -		 * Write any modified data cache blocks out to memory and
> -		 * invalidate the corresponding blocks in the instruction cache.
> -		 */
> -		bpf_flush_icache(jit_data->ro_header, ctx->ro_insns + ctx->ninsns);
>   		for (i = 0; i < prog->len; i++)
>   			ctx->offset[i] = ninsns_rvoff(ctx->offset[i]);
>   		bpf_prog_fill_jited_linfo(prog, ctx->offset);

Reviewed-by: Pu Lehui <pulehui@huawei.com>

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