Subject: Re: [PATCH bpf-next v4] bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES

From: Martin KaFai Lau <[email-masked]>
Date: Fri, 17 Feb 2023 12:32:36 -0800

On 2/15/23 10:54 AM, Alexander Lobakin wrote:
> +#if BITS_PER_LONG == 64 && PAGE_SIZE == SZ_4K
> +/* tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c:%MAX_PKT_SIZE
> + * must be updated accordingly when any of these changes, otherwise BPF
> + * selftests will fail.
> + */
> +#ifdef __s390x__
> +#define TEST_MAX_PKT_SIZE 3216
> +#else
> +#define TEST_MAX_PKT_SIZE 3408

I have to revert this patch for now. It is not right to assume cache line size:
https://lore.kernel.org/bpf/[email-masked]/

Please resubmit and consider if this static_assert is really needed in the 
kernel test_run.c.

> +#endif
> +static_assert(SKB_WITH_OVERHEAD(TEST_XDP_FRAME_SIZE - XDP_PACKET_HEADROOM) ==
> +	      TEST_MAX_PKT_SIZE);
> +#endif