Message-ID: <dd4dc3b2-115d-5973-6882-9b9916182a88@intel.com>
Date:   Mon, 20 Feb 2023 16:48:30 +0100
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Subject: Re: [PATCH bpf-next v4] bpf, test_run: fix &xdp_frame misplacement
 for LIVE_FRAMES
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To:     Martin KaFai Lau <martin.lau@linux.dev>
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>
 <cd2fa388-573c-99d7-d199-f588d8d38bd5@linux.dev>
From:   Alexander Lobakin <aleksander.lobakin@intel.com>
In-Reply-To: <cd2fa388-573c-99d7-d199-f588d8d38bd5@linux.dev>
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From: Martin Kafai Lau <martin.lau@linux.dev>
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:

Userspace part tries to guess it :D Anyway, let's keep as it was for now.
Sent v5 without the static assertion, I hope it can still hit current
cycle? Or too late already?

> 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
> 

Thanks,
Olek