Toshi explains:

"No, the default values need to be set to the fallback types,
 i.e. minimal supported mode.  For WC and WT, UC is the fallback type.

 When PAT is disabled, pat_init() does update the tables below to
 enable WT per the default BIOS setup.  However, when PAT is enabled,
 but CPU has PAT -errata, WT falls back to UC per the default values."

Revert: ca1fec58 'x86/mm/pat: Adjust default caching mode translation tables'
Requested-by: Toshi Kani <toshi.kani@hp.com>
Cc: Jan Beulich <jbeulich@suse.de>
Link: http://lkml.kernel.org/r/1437577776.3214.252.camel@hp.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>