tree edf61516631f9b7c2bcb37ab70d3b430f731b2f4
parent df610d678893c85b82d3a68eea0d87dd4e03e615
author Dave Hansen <dave.hansen@intel.com> 1475857422 -0700
committer Thomas Gleixner <tglx@linutronix.de> 1475922404 +0200

x86/pkeys: Make protection keys an "eager" feature

Our XSAVE features are divided into two categories: those that
generate FPU exceptions, and those that do not.  MPX and pkeys do
not generate FPU exceptions and thus can not be used lazily.  We
disable them when lazy mode is forced on.

We have a pair of masks to collect these two sets of features, but
XFEATURE_MASK_PKRU was added to the wrong mask: XFEATURE_MASK_LAZY.
Fix it by moving the feature to XFEATURE_MASK_EAGER.

Note: this only causes problem if you boot with lazy FPU mode
(eagerfpu=off) which is *not* the default.  It also only affects
hardware which is not currently publicly available.  It looks like
eager mode is going away, but we still need this patch applied
to any kernel that has protection keys and lazy mode, which is 4.6
through 4.8 at this point, and 4.9 if the lazy removal isn't sent
to Linus for 4.9.

Fixes: c8df40098451 ("x86/fpu, x86/mm/pkeys: Add PKRU xsave fields and data structures")
Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20161007162342.28A49813@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>