x86/fpu: Remove struct fpu::fpregs_active

The previous changes paved the way for the removal of the
fpu::fpregs_active state flag - we now only have the
fpu::fpstate_active and fpu::last_cpu fields left.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20170923130016.21448-21-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -526,14 +526,12 @@ static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
  */
 static inline void fpregs_deactivate(struct fpu *fpu)
 {
-	fpu->fpregs_active = 0;
 	this_cpu_write(fpu_fpregs_owner_ctx, NULL);
 	trace_x86_fpu_regs_deactivated(fpu);
 }
 
 static inline void fpregs_activate(struct fpu *fpu)
 {
-	fpu->fpregs_active = 1;
 	this_cpu_write(fpu_fpregs_owner_ctx, fpu);
 	trace_x86_fpu_regs_activated(fpu);
 }
@@ -552,8 +550,6 @@ static inline void fpregs_activate(struct fpu *fpu)
 static inline void
 switch_fpu_prepare(struct fpu *old_fpu, int cpu)
 {
-	WARN_ON_FPU(old_fpu->fpregs_active != old_fpu->fpstate_active);
-
 	if (old_fpu->fpstate_active) {
 		if (!copy_fpregs_to_fpstate(old_fpu))
 			old_fpu->last_cpu = -1;
@@ -561,7 +557,6 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
 			old_fpu->last_cpu = cpu;
 
 		/* But leave fpu_fpregs_owner_ctx! */
-		old_fpu->fpregs_active = 0;
 		trace_x86_fpu_regs_deactivated(old_fpu);
 	} else
 		old_fpu->last_cpu = -1;

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

@@ -298,29 +298,6 @@ struct fpu {
 	 */
 	unsigned char			fpstate_active;
 
-	/*
-	 * @fpregs_active:
-	 *
-	 * This flag determines whether a given context is actively
-	 * loaded into the FPU's registers and that those registers
-	 * represent the task's current FPU state.
-	 *
-	 * Note the interaction with fpstate_active:
-	 *
-	 *   # task does not use the FPU:
-	 *   fpstate_active == 0
-	 *
-	 *   # task uses the FPU and regs are active:
-	 *   fpstate_active == 1 && fpregs_active == 1
-	 *
-	 *   # the regs are inactive but still match fpstate:
-	 *   fpstate_active == 1 && fpregs_active == 0 && fpregs_owner == fpu
-	 *
-	 * The third state is what we use for the lazy restore optimization
-	 * on lazy-switching CPUs.
-	 */
-	unsigned char			fpregs_active;
-
 	/*
 	 * @state:
 	 *

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

@@ -12,7 +12,6 @@ DECLARE_EVENT_CLASS(x86_fpu,
 
 	TP_STRUCT__entry(
 		__field(struct fpu *, fpu)
-		__field(bool, fpregs_active)
 		__field(bool, fpstate_active)
 		__field(u64, xfeatures)
 		__field(u64, xcomp_bv)
@@ -20,16 +19,14 @@ DECLARE_EVENT_CLASS(x86_fpu,
 
 	TP_fast_assign(
 		__entry->fpu		= fpu;
-		__entry->fpregs_active	= fpu->fpregs_active;
 		__entry->fpstate_active	= fpu->fpstate_active;
 		if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
 			__entry->xfeatures = fpu->state.xsave.header.xfeatures;
 			__entry->xcomp_bv  = fpu->state.xsave.header.xcomp_bv;
 		}
 	),
-	TP_printk("x86/fpu: %p fpregs_active: %d fpstate_active: %d xfeatures: %llx xcomp_bv: %llx",
+	TP_printk("x86/fpu: %p fpstate_active: %d xfeatures: %llx xcomp_bv: %llx",
 			__entry->fpu,
-			__entry->fpregs_active,
 			__entry->fpstate_active,
 			__entry->xfeatures,
 			__entry->xcomp_bv

arch/x86/kernel/fpu/core.c

@@ -147,8 +147,6 @@ void fpu__save(struct fpu *fpu)
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
 	preempt_disable();
-	WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active);
-
 	trace_x86_fpu_before_save(fpu);
 	if (fpu->fpstate_active) {
 		if (!copy_fpregs_to_fpstate(fpu)) {
@@ -191,7 +189,6 @@ EXPORT_SYMBOL_GPL(fpstate_init);
 
 int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 {
-	dst_fpu->fpregs_active = 0;
 	dst_fpu->last_cpu = -1;
 
 	if (!src_fpu->fpstate_active || !static_cpu_has(X86_FEATURE_FPU))
@@ -264,7 +261,6 @@ EXPORT_SYMBOL_GPL(fpu__activate_curr);
  */
 void fpu__activate_fpstate_read(struct fpu *fpu)
 {
-	WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active);
 	/*
 	 * If fpregs are active (in the current CPU), then
 	 * copy them to the fpstate:
@@ -365,7 +361,6 @@ void fpu__current_fpstate_write_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
-	WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active);
 	/*
 	 * 'fpu' now has an updated copy of the state, but the
 	 * registers may still be out of date.  Update them with
@@ -419,8 +414,6 @@ void fpu__drop(struct fpu *fpu)
 	preempt_disable();
 
 	if (fpu == &current->thread.fpu) {
-		WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active);
-
 		if (fpu->fpstate_active) {
 			/* Ignore delayed exceptions from user space */
 			asm volatile("1: fwait\n"
@@ -428,8 +421,6 @@ void fpu__drop(struct fpu *fpu)
 				     _ASM_EXTABLE(1b, 2b));
 			fpregs_deactivate(fpu);
 		}
-	} else {
-		WARN_ON_FPU(fpu->fpregs_active);
 	}
 
 	fpu->fpstate_active = 0;

arch/x86/kernel/fpu/signal.c

@@ -171,8 +171,6 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 			sizeof(struct user_i387_ia32_struct), NULL,
 			(struct _fpstate_32 __user *) buf) ? -1 : 1;
 
-	WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active);
-
 	if (fpu->fpstate_active || using_compacted_format()) {
 		/* Save the live register state to the user directly. */
 		if (copy_fpregs_to_sigframe(buf_fx))