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

Pull low-level x86 updates from Ingo Molnar:
 "In this cycle this topic tree has become one of those 'super topics'
  that accumulated a lot of changes:

   - Add CONFIG_VMAP_STACK=y support to the core kernel and enable it on
     x86 - preceded by an array of changes. v4.8 saw preparatory changes
     in this area already - this is the rest of the work. Includes the
     thread stack caching performance optimization. (Andy Lutomirski)

   - switch_to() cleanups and all around enhancements. (Brian Gerst)

   - A large number of dumpstack infrastructure enhancements and an
     unwinder abstraction. The secret long term plan is safe(r) live
     patching plus maybe another attempt at debuginfo based unwinding -
     but all these current bits are standalone enhancements in a frame
     pointer based debug environment as well. (Josh Poimboeuf)

   - More __ro_after_init and const annotations. (Kees Cook)

   - Enable KASLR for the vmemmap memory region. (Thomas Garnier)"

[ The virtually mapped stack changes are pretty fundamental, and not
  x86-specific per se, even if they are only used on x86 right now. ]

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/asm: Get rid of __read_cr4_safe()
  thread_info: Use unsigned long for flags
  x86/alternatives: Add stack frame dependency to alternative_call_2()
  x86/dumpstack: Fix show_stack() task pointer regression
  x86/dumpstack: Remove dump_trace() and related callbacks
  x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder
  oprofile/x86: Convert x86_backtrace() to use the new unwinder
  x86/stacktrace: Convert save_stack_trace_*() to use the new unwinder
  perf/x86: Convert perf_callchain_kernel() to use the new unwinder
  x86/unwind: Add new unwind interface and implementations
  x86/dumpstack: Remove NULL task pointer convention
  fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y
  sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
  lib/syscall: Pin the task stack in collect_syscall()
  x86/process: Pin the target stack in get_wchan()
  x86/dumpstack: Pin the target stack when dumping it
  kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function
  sched/core: Add try_get_task_stack() and put_task_stack()
  x86/entry/64: Fix a minor comment rebase error
  iommu/amd: Don't put completion-wait semaphore on stack
  ...

diff --cc arch/x86/Kconfig
Simple merge

diff --cc arch/x86/entry/entry_64.S
Simple merge

diff --cc arch/x86/events/core.c
Simple merge

diff --cc arch/x86/include/asm/paravirt.h
Simple merge

diff --cc arch/x86/include/asm/paravirt_types.h
Simple merge

diff --cc arch/x86/kernel/apic/probe_32.c
Simple merge

diff --cc arch/x86/kernel/cpu/common.c
Simple merge

diff --cc arch/x86/kernel/setup.c
Simple merge

diff --cc arch/x86/kernel/smpboot.c
Simple merge

diff --cc arch/x86/xen/enlighten.c
Simple merge

diff --cc include/linux/sched.h
Simple merge

diff --cc kernel/sched/core.c
index fac6492f0b98155da75e056302c393ebb568abc4,23c6037e2d89b8cf93389d0a756b00f5bf668cbe..94732d1ab00ab9d9afdebad41642e279249776cb
--- 1/kernel/sched/core.c
--- 2/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@@ -3403,35 -3407,7 +3407,34 @@@ static void __sched notrace __schedule(
  
        balance_callback(rq);
  }
- STACK_FRAME_NON_STANDARD(__schedule); /* switch_to() */
  
 +void __noreturn do_task_dead(void)
 +{
 +      /*
 +       * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
 +       * when the following two conditions become true.
 +       *   - There is race condition of mmap_sem (It is acquired by
 +       *     exit_mm()), and
 +       *   - SMI occurs before setting TASK_RUNINNG.
 +       *     (or hypervisor of virtual machine switches to other guest)
 +       *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
 +       *
 +       * To avoid it, we have to wait for releasing tsk->pi_lock which
 +       * is held by try_to_wake_up()
 +       */
 +      smp_mb();
 +      raw_spin_unlock_wait(&current->pi_lock);
 +
 +      /* causes final put_task_struct in finish_task_switch(). */
 +      __set_current_state(TASK_DEAD);
 +      current->flags |= PF_NOFREEZE;  /* tell freezer to ignore us */
 +      __schedule(false);
 +      BUG();
 +      /* Avoid "noreturn function does return".  */
 +      for (;;)
 +              cpu_relax();    /* For when BUG is null */
 +}
 +
  static inline void sched_submit_work(struct task_struct *tsk)
  {
        if (!tsk->state || tsk_is_pi_blocked(tsk))

diff --cc kernel/sched/sched.h
Simple merge