x86/fpu: Remove struct fpu::counter

BugLink: https://bugs.launchpad.net/bugs/1801900

commit 3913cc35 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@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-6-git-send-email-riel@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@toshiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/x86/include/asm/fpu/internal.h

@@ -575,15 +575,12 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
 
 		/* 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

arch/x86/include/asm/fpu/types.h

@@ -302,17 +302,6 @@ 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:
 	 *

arch/x86/kernel/fpu/core.c

@@ -251,7 +251,6 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_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;
 
@@ -354,7 +353,6 @@ 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);
@@ -371,7 +369,6 @@ 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 */