Unmapped buffers: to be merged in several days

[Konstantin Belousov]

On Mon, Mar 11, 2013 at 03:22:47PM -0700, Jim Harris wrote:
> On Mon, Mar 11, 2013 at 2:11 PM, Konstantin Belousov <kostikbel at gmail.com>wrote:
> 
> > FWIW, I tried to get an Intel documentation for IOAT engine which should
> > allow to perform the XOR checksumming of the unmapped buffers, suitable
> > for e.g. hardware-assisted software raid5, but did not succeeded.
> >
> 
> Please note that XOR checksumming support only exists in the
> E5-1600/2400/2600/4600 series (Sandy Bridge Xeon) and C5500/C3500 series
> (Jasper Forest - based on Nehalem Xeon) processors.  The SNB Xeon series
> EDS section for IOAT isn't public, but the Jasper Forest datasheet volume 2
> does contain the register interfaces.  See sections 3.9 and section 3.10.
> The ioat HW interface for XOR is the same for both series save for some
> delta in errata.
> 
> http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/xeon-c5500-c3500-datasheet-vol-2.pdf

Thank you for this pointer too. I remember from looking at the e5-1600
registers description, that all magic happens in the channel commands,
which specifications are absent in the chipset documentation.

> 
> Also note there is an ioat driver (DMA operations only) on the
> user/jimharris/ioat branch in the FreeBSD SVN repo.  The Linux ioat driver
> with XOR support is dual-licensed BSD/GPL.
> 
Yes, I did some reading of this code.
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