linux/arch/x86/mm
Dave Hansen 76de993727 x86/pkeys: Allow configuration of init_pkru
As discussed in the previous patch, there is a reliability
benefit to allowing an init value for the Protection Keys Rights
User register (PKRU) which differs from what the XSAVE hardware
provides.

But, having PKRU be 0 (its init value) provides some nonzero
amount of optimization potential to the hardware.  It can, for
instance, skip writes to the XSAVE buffer when it knows that PKRU
is in its init state.

The cost of losing this optimization is approximately 100 cycles
per context switch for a workload which lightly using XSAVE
state (something not using AVX much).  The overhead comes from a
combinaation of actually manipulating PKRU and the overhead of
pullin in an extra cacheline.

This overhead is not huge, but it's also not something that I
think we should unconditionally inflict on everyone.  So, make it
configurable both at boot-time and from debugfs.

Changes to the debugfs value affect all processes created after
the write to debugfs.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-arch@vger.kernel.org
Cc: Dave Hansen <dave@sr71.net>
Cc: mgorman@techsingularity.net
Cc: arnd@arndb.de
Cc: linux-api@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: luto@kernel.org
Cc: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org
Link: http://lkml.kernel.org/r/20160729163023.407672D2@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-09-09 13:02:28 +02:00
..
kmemcheck x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
amdtopology.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
debug_pagetables.c x86/mm/ptdump: Make (debugfs)/kernel_page_tables read-only 2015-12-04 12:55:01 +01:00
dump_pagetables.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
extable.c Merge branch 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-07-25 18:18:04 -07:00
fault.c x86/pkeys: Add fault handling for PF_PK page fault bit 2016-09-09 13:02:26 +02:00
gup.c Merge branch 'mm-pkeys-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-20 19:08:56 -07:00
highmem_32.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
hugetlbpage.c x86: mm: use hugetlb_bad_size() 2016-05-19 19:12:14 -07:00
ident_map.c x86/power/64: Always create temporary identity mapping correctly 2016-08-08 22:04:30 +02:00
init_32.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
init_64.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
init.c x86/mm/KASLR: Increase BRK pages for KASLR memory randomization 2016-08-10 14:45:19 +02:00
iomap_32.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
ioremap.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
kasan_init_64.c kasan: add newline to messages 2016-07-15 14:54:27 +09:00
kaslr.c treewide: replace config_enabled() with IS_ENABLED() (2nd round) 2016-08-26 17:39:35 -07:00
kmmio.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
Makefile x86/mm: Implement ASLR for kernel memory regions 2016-07-08 17:33:46 +02:00
mm_internal.h x86: Enable PAT to use cache mode translation tables 2014-11-16 11:04:26 +01:00
mmap.c Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-15 10:45:39 -07:00
mmio-mod.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
mpx.c Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-03-24 09:47:32 -07:00
numa_32.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
numa_64.c
numa_emulation.c
numa_internal.h
numa.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
pageattr-test.c x86/mm/pat: Make mm/pageattr[-test].c explicitly non-modular 2015-08-25 09:48:38 +02:00
pageattr.c Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-07-25 17:32:28 -07:00
pat_internal.h x86/mm/pat: Convert to pr_*() usage 2015-05-27 14:40:59 +02:00
pat_rbtree.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
pat.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
pf_in.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
pf_in.h
pgtable_32.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
pgtable.c arch: x86: charge page tables to kmemcg 2016-07-26 16:19:19 -07:00
physaddr.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
physaddr.h
pkeys.c x86/pkeys: Allow configuration of init_pkru 2016-09-09 13:02:28 +02:00
setup_nx.c Revert "x86/mm/32: Set NX in __supported_pte_mask before enabling paging" 2016-04-26 19:52:57 +02:00
srat.c Merge branch 'x86-headers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-01 14:23:42 -04:00
testmmiotrace.c
tlb.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00