Re: [PATCH 0/2] lio-target: Add support for libcrypto crc32c and crc32-intel offload

Hannes Reinecke
2010-09-13T09:21:33Z

Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
>
> 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.
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?

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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