On Mon, 2010-09-13 at 11:21 +0200, Hannes Reinecke wrote: > Nicholas A. Bellinger wrote: > > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx> > > > > Greetings all, > > > > This patch series converts the LIO-Target fabric module from using a legacy > > internal slicing by 1x CRC32C algorithm to the slicing by 1x CRC32C available in > > crc32c.ko, as well as initial support for the Nehalem series crc32c-intel.ko > > instruction offload available since v2.6.27 in late 2008. > > > > So far this series has been lightly tested with a handful of Open-iSCSI client VMs > > with the optimized crc32c-intel.ko offload case, and there appears to be some > > HeaderDigest failures for one case with RHEL6 B2 x86_64, while Ubuntu i686 on > > v2.6.27 and OpenSuse 11.2 x86_64 on v2.6.31 work as expected with HeaderDigest=CRC32C > > and DataDigest=CRC32C using the offload on the LIO-Target side. > > > > Currently this patch disables the new iSCSI TPG attribute crc32c_x86_offload > > to force the crc32c.ko slicing by x1 CRC32C algorithm until these compatibility > > issues with existing libcrc32c clients can be properly resolved with the Nehalem > > CRC32C offload instructions running on the LIO-Target side. > > > Due to a customer issue I had to revisit the CRC32 issue recently. > And according to you the main reason for using your own CRC routines > had been endianness issues. Indeed, this has historically been the case for LIO-Target and Core-iSCSI. I noticed the issue with libcrypto while porting the latter on a old G4 TI-book waaay back during v2.6.10-rc3 days. > IE the in-kernel crc32c routines apparently weren't able to > calculate the checksum in an endianness-independent manner. > So a CRC calculated on a BE machine would fail to be validated by a > LE machine and vice versa. > > Has this been fixed / verified? > >From taking a look at crypto/crc32c.c it still appears AFAICT to not be big endian safe. I was planning to test this patch on some powerpc/ppc hardware with v2.6.36-rc4 in the next days, but it looks like lio-core-2.6.git will need a seperate crypto/crc32c.c patch to function properly on big endian arches. Thanks for mentioning this point Hannes! --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
