Re: [Xen-devel] [PATCH 4 of 5] blkif.h: Document the RedHat and Citrix blkif multi-page ring extensions

["Justin T. Gibbs" <justing@xxxxxxxxxxxxxxxx>]

On Feb 14, 2012, at 6:56 AM, Konrad Rzeszutek Wilk wrote:

> > > The state is a bit embarrassing on the BSD side.  FreeBSD has had a
> > > multi-page ring extension since October of 2010.  Unfortunately, I wrote
> > > this extension before stumbling upon the Citrix blkif patch or the
> > > extension being used on EC2.  It is closest to the EC2 implementation,
> > > but not quite compatible.  The saving grace is that I don't know of any
> > > deployments of this back-end outside of Spectra, and we have not shipped
> > > it to customers, so I plan to upstream block front and back drivers that
>
> Excellent <crosses out another TODO on the "get done at some point list">
>
> > > only implement the Citrix and EC2 style extension once blkif.h settles.  A
>
> So what is the Red Hat version of this extension? Where can I find it?
> Is it in the 2.6.18 hg tree?

The RedHat distribution on EC2 seems to be running a derivation of
the patch described in this thread:

    
http://xen.1045712.n5.nabble.com/PATCH-multi-page-blkfront-blkback-patch-td2527534.html

However, the EC2 backend additionally publishes "max-ring-pages"
as described in my changes to blkif.h.

You can review the FreeBSD implementation of both extensions in the
latest versions of blkfront and back here:

http://svnweb.freebsd.org/base/head/sys/dev/xen/

--
Justin





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