Re: [PATCH bpf-next v7 1/2] bpf: Introduce jit_required flag and refactor kfunc path

[Leon Hwang <leon.hwang@linux.dev>]

On 6/7/26 08:56, Tiezhu Yang wrote:
> On 2026/7/4 上午9:57, KaFai Wan wrote:
>> On Sat, 2026-07-04 at 00:14 +0800, Tiezhu Yang wrote:
>>> On 7/3/26 21:55, KaFai Wan wrote:
>>>> On Thu, 2026-07-02 at 22:36 +0800, Tiezhu Yang wrote:
> 
> ...
> 
>>>
>>> IIUC, there are two places to modify so far:
>>> (1) struct bpf_prog
>>
>> yes
>>
>>> (2) bpf_prog_has_kfunc_call()
>>
>> I think we can remove this func.
>>
>> actually, I feed your patch to dsv4-pro and gpt-5.4 yesterday, both
>> point out the we should do this
>> and change the log message.
>>
>> diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c
>> index 12a8a4eb757f..7fb92b5fa415 100644
>> --- a/kernel/bpf/fixups.c
>> +++ b/kernel/bpf/fixups.c
>> @@ -1378,7 +1378,6 @@ int bpf_fixup_call_args(struct bpf_verifier_env
>> *env)
>>   #ifndef CONFIG_BPF_JIT_ALWAYS_ON
>>       struct bpf_prog *prog = env->prog;
>>       struct bpf_insn *insn = prog->insnsi;
>> -    bool has_kfunc_call = bpf_prog_has_kfunc_call(prog);
>>       int depth;
>>   #endif
>>       int i, err = 0;
>> @@ -1404,7 +1403,7 @@ int bpf_fixup_call_args(struct bpf_verifier_env
>> *env)
>>               return err;
>>       }
>>   #ifndef CONFIG_BPF_JIT_ALWAYS_ON
>> -    if (has_kfunc_call) {
>> +    if (prog->jit_required) {


Agreed with this change.

Then, think it harder, pls.

Can we clean some code of __bpf_prog_select_runtime() btw?

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 649cce41e13f..bad55e119cb5 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -120,6 +120,9 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned
int size, gfp_t gfp_extra_flag
 		return NULL;
 	}

+#ifdef CONFIG_BPF_JIT_ALWAYS_ON
+	fp->jit_required = true;
+#endif
 	fp->pages = size / PAGE_SIZE;
 	fp->aux = aux;
 	fp->aux->main_prog_aux = aux;
@@ -2614,15 +2617,11 @@ struct bpf_prog
*__bpf_prog_select_runtime(struct bpf_verifier_env *env, struct
 	/* In case of BPF to BPF calls, verifier did all the prep
 	 * work with regards to JITing, etc.
 	 */
-	bool jit_needed = false;
+	bool jit_needed = fp->jit_required;

 	if (fp->bpf_func)
 		goto finalize;

-	if (IS_ENABLED(CONFIG_BPF_JIT_ALWAYS_ON) ||
-	    bpf_prog_has_kfunc_call(fp))
-		jit_needed = true;
-
 	if (!bpf_prog_select_interpreter(fp))
 		jit_needed = true;

WDYT?

Thanks,
Leon

>>           verbose(env, "calling kernel functions are not allowed in
>> non-JITed programs\n");
>>           return -EINVAL;
>> [...]