Merge commit 'upstream-x86-entry' into WIP.x86/mm

Pull in a minimal set of v4.15 entry code changes, for a base for the MM isolation patches.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/smpboot.c

@@ -962,8 +962,7 @@ void common_cpu_up(unsigned int cpu, struct task_struct *idle)
 #ifdef CONFIG_X86_32
 	/* Stack for startup_32 can be just as for start_secondary onwards */
 	irq_ctx_init(cpu);
-	per_cpu(cpu_current_top_of_stack, cpu) =
-		(unsigned long)task_stack_page(idle) + THREAD_SIZE;
+	per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
 #else
 	initial_gs = per_cpu_offset(cpu);
 #endif