Re: net/smc/smc_llc.c:26:2: warning: field within 'struct smc_llc_hdr' is less aligned than 'union smc_llc_hdr::(anonymous at net/smc/smc_llc.c:26:2)' and is usually due to 'struct smc_llc_hdr' being packed, which can lead to unaligned accesses

["Arnd Bergmann" <arnd@arndb.de>]

On Sat, Sep 17, 2022, at 10:09 AM, kernel test robot wrote:
> Hi Karsten,
>
> FYI, the error/warning still remains.
>

>
>>> net/smc/smc_llc.c:26:2: warning: field  within 'struct smc_llc_hdr' is less aligned than 'union smc_llc_hdr::(anonymous at net/smc/smc_llc.c:26:2)' and is usually due to 'struct smc_llc_hdr' being packed, which can lead to unaligned accesses [-Wunaligned-access]
>            union {
>            ^
>    1 warning generated.
>
>
> vim +26 net/smc/smc_llc.c
>
>     23	
>     24	struct smc_llc_hdr {
>     25		struct smc_wr_rx_hdr common;
>   > 26		union {
>     27			struct {
>     28				u8 length;	/* 44 */
>     29		#if defined(__BIG_ENDIAN_BITFIELD)
>     30				u8 reserved:4,
>     31				   add_link_rej_rsn:4;
>     32	#elif defined(__LITTLE_ENDIAN_BITFIELD)
>     33				u8 add_link_rej_rsn:4,
>     34				   reserved:4;
>     35	#endif
>     36			};
>     37			u16 length_v2;	/* 44 - 8192*/
>     38		};
>     39		u8 flags;
>     40	} __packed;		/* format defined in
>     41				 * IBM Shared Memory Communications Version 2

I think the __packed annotation should be moved to the
length_v2 field instead of the outer struct to resolve that.

    Arnd