x86/fpu: Always init the state in fpu__clear()

fpu__clear() only initializes the state if the CPU has FPU support.
This initialisation is also required for FPU-less systems and takes
place in math_emulate(). Since fpu__initialize() only performs the
initialization if ->initialized is zero it does not matter that it
is invoked each time an opcode is emulated. It makes the removal of
->initialized easier if the struct is also initialized in the FPU-less
case at the same time.

Move fpu__initialize() before the FPU feature check so it is also
performed in the FPU-less case too.

 [ bp: Massage a bit. ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Bill Metzenthen <billm@melbpc.org.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-5-bigeasy@linutronix.de

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

@@ -24,7 +24,6 @@
 /*
  * High level FPU state handling functions:
  */
-extern void fpu__initialize(struct fpu *fpu);
 extern void fpu__prepare_read(struct fpu *fpu);
 extern void fpu__prepare_write(struct fpu *fpu);
 extern void fpu__save(struct fpu *fpu);

arch/x86/kernel/fpu/core.c

@@ -223,7 +223,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
  * Activate the current task's in-memory FPU context,
  * if it has not been used before:
  */
-void fpu__initialize(struct fpu *fpu)
+static void fpu__initialize(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
@@ -236,7 +236,6 @@ void fpu__initialize(struct fpu *fpu)
 		fpu->initialized = 1;
 	}
 }
-EXPORT_SYMBOL_GPL(fpu__initialize);
 
 /*
  * This function must be called before we read a task's fpstate.
@@ -365,8 +364,8 @@ void fpu__clear(struct fpu *fpu)
 	/*
 	 * Make sure fpstate is cleared and initialized.
 	 */
-	if (static_cpu_has(X86_FEATURE_FPU)) {
 	fpu__initialize(fpu);
+	if (static_cpu_has(X86_FEATURE_FPU)) {
 		user_fpu_begin();
 		copy_init_fpstate_to_fpregs();
 	}

arch/x86/math-emu/fpu_entry.c

@@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info)
 	unsigned long code_base = 0;
 	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
 	struct desc_struct code_descriptor;
-	struct fpu *fpu = &current->thread.fpu;
-
-	fpu__initialize(fpu);
 
 #ifdef RE_ENTRANT_CHECKING
 	if (emulating) {