linux-kernel - [PATCH 4.4 33/48] x86/fpu: Remove struct fpu::counter

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Date:   Thu, 18 Oct 2018 19:55:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Rik van Riel <riel@...hat.com>,
        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>,
        Thomas Gleixner <tglx@...utronix.de>, pbonzini@...hat.com,
        Ingo Molnar <mingo@...nel.org>,
        Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
Subject: [PATCH 4.4 33/48] x86/fpu: Remove struct fpu::counter

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rik van Riel <riel@...hat.com>

commit 3913cc3507575273beb165a5e027a081913ed507 upstream.

With the lazy FPU code gone, we no longer use the counter field
in struct fpu for anything. Get rid it.

Signed-off-by: Rik van Riel <riel@...hat.com>
Reviewed-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: Thomas Gleixner <tglx@...utronix.de>
Cc: pbonzini@...hat.com
Link: http://lkml.kernel.org/r/1475627678-20788-6-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/fpu/internal.h |    3 ---
 arch/x86/include/asm/fpu/types.h    |   11 -----------
 arch/x86/kernel/fpu/core.c          |    3 ---
 3 files changed, 17 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -575,15 +575,12 @@ switch_fpu_prepare(struct fpu *old_fpu,
 
 		/* Don't change CR0.TS if we just switch! */
 		if (fpu.preload) {
-			new_fpu->counter++;
 			__fpregs_activate(new_fpu);
 			prefetch(&new_fpu->state);
 		}
 	} else {
-		old_fpu->counter = 0;
 		old_fpu->last_cpu = -1;
 		if (fpu.preload) {
-			new_fpu->counter++;
 			if (fpu_want_lazy_restore(new_fpu, cpu))
 				fpu.preload = 0;
 			else
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -303,17 +303,6 @@ struct fpu {
 	unsigned char			fpregs_active;
 
 	/*
-	 * @counter:
-	 *
-	 * This counter contains the number of consecutive context switches
-	 * during which the FPU stays used. If this is over a threshold, the
-	 * lazy FPU restore logic becomes eager, to save the trap overhead.
-	 * This is an unsigned char so that after 256 iterations the counter
-	 * wraps and the context switch behavior turns lazy again; this is to
-	 * deal with bursty apps that only use the FPU for a short time:
-	 */
-	unsigned char			counter;
-	/*
 	 * @state:
 	 *
 	 * In-memory copy of all FPU registers that we save/restore
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -250,7 +250,6 @@ static void fpu_copy(struct fpu *dst_fpu
 
 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 {
-	dst_fpu->counter = 0;
 	dst_fpu->fpregs_active = 0;
 	dst_fpu->last_cpu = -1;
 
@@ -353,7 +352,6 @@ void fpu__restore(struct fpu *fpu)
 	kernel_fpu_disable();
 	fpregs_activate(fpu);
 	copy_kernel_to_fpregs(&fpu->state);
-	fpu->counter++;
 	kernel_fpu_enable();
 }
 EXPORT_SYMBOL_GPL(fpu__restore);
@@ -370,7 +368,6 @@ EXPORT_SYMBOL_GPL(fpu__restore);
 void fpu__drop(struct fpu *fpu)
 {
 	preempt_disable();
-	fpu->counter = 0;
 
 	if (fpu->fpregs_active) {
 		/* Ignore delayed exceptions from user space */