Message-ID: <cd2fa388-573c-99d7-d199-f588d8d38bd5@linux.dev>
Date:   Fri, 17 Feb 2023 12:32:36 -0800
MIME-Version: 1.0
Subject: Re: [PATCH bpf-next v4] bpf, test_run: fix &xdp_frame misplacement
 for LIVE_FRAMES
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To:     Alexander Lobakin <aleksander.lobakin@intel.com>
Cc:     =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@redhat.com>,
        Song Liu <song@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>, bpf@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>
References: <20230215185440.4126672-1-aleksander.lobakin@intel.com>
From:   Martin KaFai Lau <martin.lau@linux.dev>
In-Reply-To: <20230215185440.4126672-1-aleksander.lobakin@intel.com>
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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/50c35055-afa9-d01e-9a05-ea5351280e4f@intel.com/

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