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

Pull x86 fpu changes from Ingo Molnar:
 "Various x86 FPU handling cleanups, refactorings and fixes (Borislav
  Petkov, Oleg Nesterov, Rik van Riel)"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  x86/fpu: Kill eager_fpu_init_bp()
  x86/fpu: Don't allocate fpu->state for swapper/0
  x86/fpu: Rename drop_init_fpu() to fpu_reset_state()
  x86/fpu: Fold __drop_fpu() into its sole user
  x86/fpu: Don't abuse drop_init_fpu() in flush_thread()
  x86/fpu: Use restore_init_xstate() instead of math_state_restore() on kthread exec
  x86/fpu: Introduce restore_init_xstate()
  x86/fpu: Document user_fpu_begin()
  x86/fpu: Factor out memset(xstate, 0) in fpu_finit() paths
  x86/fpu: Change xstateregs_get()/set() to use ->xsave.i387 rather than ->fxsave
  x86/fpu: Don't abuse FPU in kernel threads if use_eager_fpu()
  x86/fpu: Always allow FPU in interrupt if use_eager_fpu()
  x86/fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu()
  x86/fpu: Also check fpu_lazy_restore() when use_eager_fpu()
  x86/fpu: Use task_disable_lazy_fpu_restore() helper
  x86/fpu: Use an explicit if/else in switch_fpu_prepare()
  x86/fpu: Introduce task_disable_lazy_fpu_restore() helper
  x86/fpu: Move lazy restore functions up a few lines
  x86/fpu: Change math_error() to use unlazy_fpu(), kill (now) unused save_init_fpu()
  x86/fpu: Don't do __thread_fpu_end() if use_eager_fpu()
  ...

1 files changed, 12 insertions, 7 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 0c8992dbead5..8213da62b1b7 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -89,8 +89,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 
 	dst->thread.fpu_counter = 0;
 	dst->thread.fpu.has_fpu = 0;
-	dst->thread.fpu.last_cpu = ~0;
 	dst->thread.fpu.state = NULL;
+	task_disable_lazy_fpu_restore(dst);
 	if (tsk_used_math(src)) {
 		int err = fpu_alloc(&dst->thread.fpu);
 		if (err)
@@ -151,13 +151,18 @@ void flush_thread(void)
 
 	flush_ptrace_hw_breakpoint(tsk);
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
-	drop_init_fpu(tsk);
-	/*
-	 * Free the FPU state for non xsave platforms. They get reallocated
-	 * lazily at the first use.
-	 */
-	if (!use_eager_fpu())
+
+	if (!use_eager_fpu()) {
+		/* FPU state will be reallocated lazily at the first use. */
+		drop_fpu(tsk);
 		free_thread_xstate(tsk);
+	} else if (!used_math()) {
+		/* kthread execs. TODO: cleanup this horror. */
+		if (WARN_ON(init_fpu(tsk)))
+			force_sig(SIGKILL, tsk);
+		user_fpu_begin();
+		restore_init_xstate();
+	}
 }
 
 static void hard_disable_TSC(void)