[PATCH v3 2/2] net: have checksum routines accept unaligned data

[Mattias Rönnblom]

On 2022-07-11 15:25, Olivier Matz wrote:
> On Mon, Jul 11, 2022 at 02:11:32PM +0200, Mattias Rönnblom wrote:
>> __rte_raw_cksum() (used by rte_raw_cksum() among others) accessed its
>> data through an uint16_t pointer, which allowed the compiler to assume
>> the data was 16-bit aligned. This in turn would, with certain
>> architectures and compiler flag combinations, result in code with SIMD
>> load or store instructions with restrictions on data alignment.
>>
>> This patch keeps the old algorithm, but data is read using memcpy()
>> instead of direct pointer access, forcing the compiler to always
>> generate code that handles unaligned input. The __may_alias__ GCC
>> attribute is no longer needed.
>>
>> The data on which the Internet checksum functions operates are almost
>> always 16-bit aligned, but there are exceptions. In particular, the
>> PDCP protocol header may (literally) have an odd size.
>>
>> Performance impact seems to range from none to a very slight
>> regression.
>>
>> Bugzilla ID: 1035
>> Cc: stable at dpdk.org
> 
> Fixes: 6006818cfb26 ("net: new checksum functions")
> 
>> ---
>>
>> v3:
>>    * Use RTE_ALIGN_FLOOR() in the pointer arithmetic (Olivier Matz).
>> v2:
>>    * Simplified the odd-length conditional (Morten Brørup).
>>
>> Reviewed-by: Morten Brørup <mb at smartsharesystems.com>
>>
>> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> 
> Acked-by: Olivier Matz <olivier.matz at 6wind.com>
> 
> Thank you!

Are there any plans to merge this patchset?