Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fpu updates from Ingo Molnar:
 "Initial round of kernel_fpu_begin/end cleanups from Oleg Nesterov,
  plus a cleanup from Borislav Petkov"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, fpu: Fix math_state_restore() race with kernel_fpu_begin()
  x86, fpu: Don't abuse has_fpu in __kernel_fpu_begin/end()
  x86, fpu: Introduce per-cpu in_kernel_fpu state
  x86/fpu: Use a symbolic name for asm operand

1 files changed, 5 insertions, 7 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c74f2f5652da..9d2073e2ecc9 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -859,18 +859,16 @@ void math_state_restore(void)
 		local_irq_disable();
 	}
 
+	/* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
+	kernel_fpu_disable();
 	__thread_fpu_begin(tsk);
-
-	/*
-	 * Paranoid restore. send a SIGSEGV if we fail to restore the state.
-	 */
 	if (unlikely(restore_fpu_checking(tsk))) {
 		drop_init_fpu(tsk);
 		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
-		return;
+	} else {
+		tsk->thread.fpu_counter++;
 	}
-
-	tsk->thread.fpu_counter++;
+	kernel_fpu_enable();
 }
 EXPORT_SYMBOL_GPL(math_state_restore);