linux-kernel - [PATCH 0/5] x86/fpu: eagerfpu fixes, speedups, and default enablement

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Date:	Fri, 22 Jan 2016 16:56:01 -0800
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Borislav Petkov <bp@...en8.de>, Fenghua Yu <fenghua.yu@...el.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	yu-cheng yu <yu-cheng.yu@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 0/5] x86/fpu: eagerfpu fixes, speedups, and default enablement

Hi all-

Patches 1, 2, and 3 are fixes.

Patch 4 is probably a small speedup.  It also only matters in lazy
FPU mode, which means that, most likely, no one cares.  Apply or
don't -- I don't care much.

Patch 5 is, in some sense, a radical change.  Currently we select
eager or lazy mode depending on CPU type.  I think that lazy mode
sucks and that we should deprecate and remove it.

With patches 1-3 applied, I think that eagerfpu works on all
systems.  Patch 5 will use it on all systems subject to a chicken
flag -- eagerfpu=off will still disable it.

I propose that we apply patch 5, let it soak in -next until the 4.6
merge window opens, possibly let it actually land in 4.6, and then
remove lazy mode entirely for 4.7.  This will open up enormous
cleanup possibilities, and it will make the fpu code vastly more
comprehensible.

Thoughts?

Andy Lutomirski (5):
  x86/fpu: Fix math emulation in eager fpu mode
  x86/fpu: Fix FNSAVE usage in eagerfpu mode
  x86/fpu: Fold fpu_copy into fpu__copy
  x86/fpu: Speed up lazy FPU restores slightly
  x86/fpu: Default eagerfpu=on on all CPUs

 arch/x86/include/asm/fpu/internal.h |  3 ++-
 arch/x86/kernel/fpu/core.c          | 52 +++++++++++++++++++------------------
 arch/x86/kernel/fpu/init.c          | 13 ++++------
 arch/x86/kernel/traps.c             |  3 +--
 4 files changed, 35 insertions(+), 36 deletions(-)

-- 
2.5.0