linux-kernel - [PATCH 0/6] add support for new persistent memory instructions

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Date:	Tue, 11 Nov 2014 11:43:10 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	H Peter Anvin <h.peter.anvin@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, x86@...nel.org
Subject: [PATCH 0/6] add support for new persistent memory instructions

This patch set adds support for two new persistent memory instructions, pcommit
and clwb.  These instructions were announced in the document "Intel
Architecture Instruction Set Extensions Programming Reference" with reference
number 319433-022.

https://software.intel.com/sites/default/files/managed/0d/53/319433-022.pdf

These patches apply cleanly to v3.18-rc4.

Here are some things of note:

 - As with the clflushopt patches before this, I'm assuming that the addressing
   mode generated by the original clflush instruction will match the new
   clflush instruction with the 0x66 prefix for clflushopt, and for the
   xsaveopt instruction with the 0x66 prefix for clwb.  For all the test cases
   that I've come up with and for the new clwb code generated by this patch
   series, this has proven to be true on my test machine.

 - According to the SDM, xsaveopt has a form where it has a REX.W prefix.  I
   believe that this prefix will not be generated by gcc in x86_64 kernel code.
   Based on this, I don't believe I need to account for this extra prefix when
   dealing with the assembly language created for clwb.  Please correct me if
   I'm wrong.

 - The last three patches in this series update existing uses of clflushopt to
   use clwb instead.  The assertion is that clwb is preferable to clflushopt in
   these cases because after a clwb the cache line will be clean and ready for
   eviction, but that there is a possibility that it might be referenced again
   in the future while it is still in the CPU cache, giving us a performance
   boost.

Cc: H Peter Anvin <h.peter.anvin@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: David Airlie <airlied@...ux.ie>
Cc: dri-devel@...ts.freedesktop.org
Cc: x86@...nel.org

Ross Zwisler (6):
  x86: Add support for the pcommit instruction
  x86/alternative: Add alternative_io_2
  x86: Add support for the clwb instruction
  x86: Use clwb in clflush_cache_range
  x86: Use clwb in drm_clflush_page
  x86: Use clwb in drm_clflush_virt_range

 arch/x86/include/asm/alternative.h   | 14 ++++++++++++++
 arch/x86/include/asm/cpufeature.h    |  2 ++
 arch/x86/include/asm/special_insns.h | 16 ++++++++++++++++
 arch/x86/mm/pageattr.c               |  8 ++++----
 drivers/gpu/drm/drm_cache.c          | 12 ++++++------
 5 files changed, 42 insertions(+), 10 deletions(-)

-- 
1.9.3

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