Le 26/02/2024 à 17:44, Guenter Roeck a écrit : > On 2/26/24 03:34, Christophe Leroy wrote: >> >> >> Le 23/02/2024 à 23:11, Charlie Jenkins a écrit : >>> The test cases for ip_fast_csum and csum_ipv6_magic were not properly >>> aligning the IP header, which were causing failures on architectures >>> that do not support misaligned accesses like some ARM platforms. To >>> solve this, align the data along (14 + NET_IP_ALIGN) bytes which is the >>> standard alignment of an IP header and must be supported by the >>> architecture. >> >> I'm still wondering what we are really trying to fix here. >> >> All other tests are explicitely testing that it works with any alignment. >> >> Shouldn't ip_fast_csum() and csum_ipv6_magic() work for any alignment as >> well ? I would expect it, I see no comment in arm code which explicits >> that assumption around those functions. >> >> Isn't the problem only the following line, because csum_offset is >> unaligned ? >> >> csum = *(__wsum *)(random_buf + i + csum_offset); >> >> Otherwise, if there really is an alignment issue for the IPv6 source or >> destination address, isn't it enough to perform a 32 bits alignment ? >> > > It isn't just arm. > > Question should be what alignments the functions are supposed to be able > to handle, not what they are optimized for. If byte and/or half word > alignments > are expected to be supported, there is still architecture code which would > have to be fixed. Unaligned accesses are known to fail on hppa64/parisc64 > and on sh4, for example. If unaligned accesses are expected to be handled, > it would probably make sense to add a separate test case, though, to > clarify > that the test fails due to alignment issues, not due to input parameters. > When you say "Unaligned accesses are known to fail on hppa64/parisc64 and on sh4", do you mean unaligned accesses in general or do you mean ip_fast_csum() with unaligned ip header and csum_ipv6_magic() with unaligned source and dest addresses ? Because later in this thread it is said that only ARM and NIOS2 potentially have an issue. And when you say "unaligned", to what level is that ? Is it 4-bytes alignment or more or less ? Christophe
