Failed to load eBPF byte-code on TAP device

[Stephen Hemminger]

On Wed, 15 Nov 2023 15:38:55 +0530
madhukar mythri <madhukar.mythri at gmail.com> wrote:

> Hi all,
> 
> On the RHEL9.2 with DPDK 22.11.1 version, DPDK primary application failed
> to add RSS flow on TAP sub-device, when loading the TAP BPF byte-code
> instructions.
> 
> This "struct bpf_insn l3_l4_hash_insns[]" array(from file:
> drivers/net/tap/tap_bpf_insns.h) is in eBPF bytecode instructions format,
> this eBPF failed to load on TAP PMD with the following error:
> 
> =====================
> rss_add_actions(): Failed to load BPF section 'l3_l4' (7): Argument list
> too long.
> net_failsafe: Failed to create a flow on sub_device 1."
> =====================
> On Kernel-version:  5.15.0 #9 SMP PREEMPT
> Arch: x86_64 GNU/Linux
> 
> When added some debug logs on Kernel BPF verifier code, we could see that
> instruction processed were reached to 1 Million.
> But, the Byte code has only 1698 instructions only. Why the Kernel BPF
> verifier is processing beyond 1,698 instructions ?
> 
> The same byte-code(with DPDK-22.11.1) worked well with RHEL8.x and not
> working in RHEL-9.x version.
> 
> Does anybody faced such issues ?
> Please let me know how to debug such issues on Byte-code.
> 
> Thanks,
> Madhukar.

Is there anything in the kernel log?