Patch "x86/pkeys: Make protection keys an "eager" feature" has been added to the 4.8-stable tree
Subsystems (2)
This is a note to let you know that I've just added the patch titled
x86/pkeys: Make protection keys an "eager" feature
to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-pkeys-make-protection-keys-an-eager-feature.patch
and it can be found in the queue-4.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
d4b05923f579c234137317cdf9a5eb69ddab76d1Mon Sep 17 00:00:00 2001
From: Dave Hansen <[email protected]>
Date: Fri, 7 Oct 2016 09:23:42 -0700
Subject: x86/pkeys: Make protection keys an "eager" feature
From: Dave Hansen <[email protected]>
commit d4b05923f579c234137317cdf9a5eb69ddab76d1 upstream.
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.
--- arch/x86/include/asm/fpu/xstate.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
arch/x86/include/asm/fpu/xstate.h +4 -3
@@ -27,11 +27,12 @@ XFEATURE_MASK_YMM | \ XFEATURE_MASK_OPMASK | \ XFEATURE_MASK_ZMM_Hi256 | \ - XFEATURE_MASK_Hi16_ZMM | \ - XFEATURE_MASK_PKRU) + XFEATURE_MASK_Hi16_ZMM)/* Supported features which require eager state saving */ -#define XFEATURE_MASK_EAGER (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR) +#define XFEATURE_MASK_EAGER (XFEATURE_MASK_BNDREGS | \ + XFEATURE_MASK_BNDCSR | \ + XFEATURE_MASK_PKRU)/* All currently supported features */ #define XCNTXT_MASK (XFEATURE_MASK_LAZY | XFEATURE_MASK_EAGER)
Patches currently in stable-queue which might be from [email protected] are
queue-4.8/x86-pkeys-make-protection-keys-an-eager-feature.patch