linux-kernel - [PATCH v3 4.4.y 3/3] x86/fpu: Finish excising 'eagerfpu'

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Date:   Wed, 11 Jul 2018 09:48:40 +0900
From:   Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
To:     stable@...r.kernel.org
Cc:     Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Quentin Casasnovas <quentin.casasnovas@...cle.com>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Razvan Ghitulete <rga@...zon.de>,
        Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...e.de>, Hugh Dickins <hughd@...gle.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 4.4.y 3/3] x86/fpu: Finish excising 'eagerfpu'

From: Andy Lutomirski <luto@...nel.org>

commit e63650840e8b053aa09ad934877e87e9941ed135 upstream

Now that eagerfpu= is gone, remove it from the docs and some
comments.  Also sync the changes to tools/.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@...cle.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/cf430dd4481d41280e93ac6cf0def1007a67fc8e.1476740397.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>

Conflicts:
	Documentation/kernel-parameters.txt
	arch/x86/include/asm/cpufeatures.h
	arch/x86/mm/pkeys.c
	tools/arch/x86/include/asm/cpufeatures.h
---
 Documentation/kernel-parameters.txt |  6 ------
 arch/x86/include/asm/cpufeature.h   |  1 -
 arch/x86/include/asm/fpu/types.h    | 23 -----------------------
 3 files changed, 30 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4df6bd7..792945c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -961,12 +961,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			See Documentation/x86/intel_mpx.txt for more
 			information about the feature.
 
-	eagerfpu=	[X86]
-			on	enable eager fpu restore
-			off	disable eager fpu restore
-			auto	selects the default scheme, which automatically
-				enables eagerfpu restore for xsaveopt.
-
 	module.async_probe [KNL]
 			Enable asynchronous probe on this module.
 
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 232621c..ac4aa86 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -104,7 +104,6 @@
 #define X86_FEATURE_EXTD_APICID	( 3*32+26) /* has extended APICID (8 bits) */
 #define X86_FEATURE_AMD_DCM     ( 3*32+27) /* multi-node processor */
 #define X86_FEATURE_APERFMPERF	( 3*32+28) /* APERFMPERF */
-/* free, was #define X86_FEATURE_EAGER_FPU	( 3*32+29) * "eagerfpu" Non lazy FPU restore */
 #define X86_FEATURE_NONSTOP_TSC_S3 ( 3*32+30) /* TSC doesn't stop in S3 state */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index dcb85a9..0d81c7d 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -310,29 +310,6 @@ struct fpu {
 	 * the registers in the FPU are more recent than this state
 	 * copy. If the task context-switches away then they get
 	 * saved here and represent the FPU state.
-	 *
-	 * After context switches there may be a (short) time period
-	 * during which the in-FPU hardware registers are unchanged
-	 * and still perfectly match this state, if the tasks
-	 * scheduled afterwards are not using the FPU.
-	 *
-	 * This is the 'lazy restore' window of optimization, which
-	 * we track though 'fpu_fpregs_owner_ctx' and 'fpu->last_cpu'.
-	 *
-	 * We detect whether a subsequent task uses the FPU via setting
-	 * CR0::TS to 1, which causes any FPU use to raise a #NM fault.
-	 *
-	 * During this window, if the task gets scheduled again, we
-	 * might be able to skip having to do a restore from this
-	 * memory buffer to the hardware registers - at the cost of
-	 * incurring the overhead of #NM fault traps.
-	 *
-	 * Note that on modern CPUs that support the XSAVEOPT (or other
-	 * optimized XSAVE instructions), we don't use #NM traps anymore,
-	 * as the hardware can track whether FPU registers need saving
-	 * or not. On such CPUs we activate the non-lazy ('eagerfpu')
-	 * logic, which unconditionally saves/restores all FPU state
-	 * across context switches. (if FPU state exists.)
 	 */
 	union fpregs_state		state;
 	/*
-- 
2.1.4