[Xen-devel] ANNOUNCE: Xen Transcendent Memory support now in stock Ubuntu and Fedora guest kernels

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

FYI, it has come to my attention that both the kernel in the
recently-released Ubuntu 12.10 (aka Quantal Quetzal) and the
kernel in Fedora 17 (after yum-update to a 3.5-or-later kernel)
are fully configured to support Transcendent Memory ("tmem").
Oracle's "UEK2" kernel has also had tmem support since its release
in early 2012.

To enable tmem support in Xen, it is necessary to specify
a Xen boot parameter ("tmem").  Specifying "dom0_mem="
and disabling dom0 autoballooning in the toolstack is also
highly recommended.  Then tmem must be explicitly enabled in
any tmem-capable guest kernel by specifying a boot parameter
(also "tmem") in each guest grub.conf.  Note that use of
tmem in dom0 is not recommended, so "tmem" should not be
provided as a dom0 boot parameter.

I'll try to write up a more complete current HOW-TO soon
since much of the Xen tmem documentation floating around
the web is a bit outdated.

Note that some security issues were reported in the
Xen hypervisor tmem implementation last summer.  Please
ensure your hypervisor is updated to patch XSA-15 before
enabling tmem on a Xen machine exposed to the internet!

Thanks,
Dan

P.S. If you build your own Linux guest kernels, a 3.5-or-later
kernel is required built with the following config variables:

CONFIG_FRONTSWAP=y
CONFIG_CLEANCACHE=y
CONFIG_XEN_TMEM=y
CONFIG_XEN_SELFBALLOONING=y


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