Re: include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct idpf_xdp_rx_desc) == sizeof(struct virtchnl2_rx_flex_desc_adv_nic_3)"

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Kernel Test Robot <lkp@intel.com>
Date: Fri, 10 Apr 2026 19:24:55 +0800

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   9a9c8ce300cd3859cc87b408ef552cd697cc2ab7
> commit: 88ca0c738c4159ce87893782b6dd964b5aa01f6e idpf: add XDP RSS hash hint
> date:   7 months ago
> config: arm-randconfig-001-20260410 (https://download.01.org/0day-ci/archive/20260410/202604101931.fN8gVxZI-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 8.5.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260410/202604101931.fN8gVxZI-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Fixes: 88ca0c738c41 ("idpf: add XDP RSS hash hint")
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202604101931.fN8gVxZI-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from include/linux/minmax.h:5,
>                     from include/linux/jiffies.h:8,
>                     from include/net/pkt_sched.h:5,
>                     from drivers/net/ethernet/intel/idpf/idpf.h:12,
>                     from drivers/net/ethernet/intel/idpf/idpf_txrx.c:4:
>>> include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct idpf_xdp_rx_desc) == sizeof(struct virtchnl2_rx_flex_desc_adv_nic_3)"
>     #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)

BTW this might be a real issue. The size of idpf_xdp_rx_desc is always
the same as in the HW specs of idpf (it's just 4 u64s == 32 bytes).
If this assertion fails, this means that the size of
virtchnl2_rx_flex_desc_adv_nic_3 could be incorrect on this setup.
I remember that on ARM32, the compiler sometimes aligns small fields
(u16 etc.) weirdly. If that's the case, we might need to mark
virtchnl2_rx_flex_desc_adv_nic_3 as
`__packed __aligned(something_that_works)`.

+ adding Kees, this is triggered on GCC, not Clang/LLVM, but maybe he
remembers ARM32 alignment issues better than me (if you have time and
don't mind, of course ;)).

>                                             ^~~~~~~~~~~~~~
>    include/linux/build_bug.h:77:34: note: in expansion of macro '__static_assert'
>     #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
>                                      ^~~~~~~~~~~~~~~
>    drivers/net/ethernet/intel/idpf/xdp.h:118:1: note: in expansion of macro 'static_assert'
>     static_assert(sizeof(struct idpf_xdp_rx_desc) ==
>     ^~~~~~~~~~~~~
> --
>    In file included from include/linux/minmax.h:5,
>                     from include/linux/jiffies.h:8,
>                     from include/net/pkt_sched.h:5,
>                     from idpf.h:12,
>                     from idpf_txrx.c:4:
>>> include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct idpf_xdp_rx_desc) == sizeof(struct virtchnl2_rx_flex_desc_adv_nic_3)"
>     #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
>                                             ^~~~~~~~~~~~~~
>    include/linux/build_bug.h:77:34: note: in expansion of macro '__static_assert'
>     #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
>                                      ^~~~~~~~~~~~~~~
>    xdp.h:118:1: note: in expansion of macro 'static_assert'
>     static_assert(sizeof(struct idpf_xdp_rx_desc) ==
Thanks,
Olek