objtool found a few cases where this code called out into instrumented
code:

  vmlinux.o: warning: objtool: acpi_idle_enter_s2idle+0xde: call to wbinvd() leaves .noinstr.text section
  vmlinux.o: warning: objtool: default_idle+0x4: call to arch_safe_halt() leaves .noinstr.text section
  vmlinux.o: warning: objtool: xen_safe_halt+0xa: call to HYPERVISOR_sched_op.constprop.0() leaves .noinstr.text section

Solve this by:

 - marking arch_safe_halt(), wbinvd(), native_wbinvd() and
   HYPERVISOR_sched_op() as __always_inline().

 - Explicitly uninlining xen_safe_halt() and pv_native_wbinvd() [they were
   already uninlined by the compiler on use as function pointers] and
   annotating them as 'noinstr'.

 - Annotating pv_native_safe_halt() as 'noinstr'.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195541.171918174@infradead.org