Re: drivers/net/ethernet/sfc/siena/selftest.c:46:15: warning: field ip within 'struct efx_loopback_payload' is less aligned than 'struct iphdr' and is usually due to 'struct efx_loopback_payload' being packed, which can lead to unaligned accesses

[Martin Habets <habetsm.xilinx@gmail.com>]

On Mon, Dec 05, 2022 at 06:09:17AM +0800, kernel test robot wrote:
> Hi Martin,
> 
> FYI, the error/warning still remains.

We are looking into this, it will take a bit of a rewrite for fix
the warning. We have not had reports of an actual unaligned accesses
happening.

Martin

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   c2bf05db6c78f53ca5cd4b48f3b9b71f78d215f1
> commit: c5a13c319e10e795850b61bc7e3447b08024be2e sfc: Add a basic Siena module
> date:   7 months ago
> config: arm-randconfig-r012-20221205
> compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 6e4cea55f0d1104408b26ac574566a0e4de48036)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install arm cross compiling tool for clang build
>         # apt-get install binutils-arm-linux-gnueabi
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c5a13c319e10e795850b61bc7e3447b08024be2e
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout c5a13c319e10e795850b61bc7e3447b08024be2e
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/net/ethernet/sfc/siena/
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> drivers/net/ethernet/sfc/siena/selftest.c:46:15: warning: field ip within 'struct efx_loopback_payload' is less aligned than 'struct iphdr' and is usually due to 'struct efx_loopback_payload' being packed, which can lead to unaligned accesses [-Wunaligned-access]
>            struct iphdr ip;
>                         ^
>    1 warning generated.
> 
> 
> vim +46 drivers/net/ethernet/sfc/siena/selftest.c
> 
> d48523cb88e0703 Martin Habets 2022-05-09  37  
> d48523cb88e0703 Martin Habets 2022-05-09  38  /*
> d48523cb88e0703 Martin Habets 2022-05-09  39   * Loopback test packet structure
> d48523cb88e0703 Martin Habets 2022-05-09  40   *
> d48523cb88e0703 Martin Habets 2022-05-09  41   * The self-test should stress every RSS vector, and unfortunately
> d48523cb88e0703 Martin Habets 2022-05-09  42   * Falcon only performs RSS on TCP/UDP packets.
> d48523cb88e0703 Martin Habets 2022-05-09  43   */
> d48523cb88e0703 Martin Habets 2022-05-09  44  struct efx_loopback_payload {
> d48523cb88e0703 Martin Habets 2022-05-09  45  	struct ethhdr header;
> d48523cb88e0703 Martin Habets 2022-05-09 @46  	struct iphdr ip;
> d48523cb88e0703 Martin Habets 2022-05-09  47  	struct udphdr udp;
> d48523cb88e0703 Martin Habets 2022-05-09  48  	__be16 iteration;
> d48523cb88e0703 Martin Habets 2022-05-09  49  	char msg[64];
> d48523cb88e0703 Martin Habets 2022-05-09  50  } __packed;
> d48523cb88e0703 Martin Habets 2022-05-09  51  
> 
> :::::: The code at line 46 was first introduced by commit
> :::::: d48523cb88e0703055c1b33e61eb644a7976f92b sfc: Copy shared files needed for Siena (part 2)
> 
> :::::: TO: Martin Habets <martinh@xilinx.com>
> :::::: CC: Jakub Kicinski <kuba@kernel.org>
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp