Re: [PATCH bpf] bpf: fix UML x86_64 compile failure

[Shung-Hsi Yu]

On Thu, Jun 13, 2024 at 04:25:20AM GMT, Maciej Żenczykowski wrote:
> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Fixes: 1ae6921009e5 ("bpf: inline bpf_get_smp_processor_id() helper")
> Signed-off-by: Maciej Żenczykowski <maze@xxxxxxxxxx>
> ---
>  kernel/bpf/verifier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 36ef8e96787e..7a354b1e6197 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -20313,7 +20313,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
>  			goto next_insn;
>  		}
>  
> -#ifdef CONFIG_X86_64
> +#if defined(CONFIG_X86_64) && !defined(CONFIG_UML)
>  		/* Implement bpf_get_smp_processor_id() inline. */
>  		if (insn->imm == BPF_FUNC_get_smp_processor_id &&
>  		    prog->jit_requested && bpf_jit_supports_percpu_insn()) {

The patch needs a change description[1].

Maybe something along the line of why pcpu_hot.cpu_number not accessible
in User-mode Linux? (I don't know bpf_get_smp_processor_id() or UML that
well, just suggesting possible change description)

1: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes