s390/smp: keep the original lowcore for CPU 0

Now that CPU 0 is not hotpluggable, it is not necessary to support
freeing its stacks. Delete all the code that migrates it to new stacks
and a new lowcore.
Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/smp.h

@@ -59,7 +59,6 @@ static inline void smp_cpus_done(unsigned int max_cpus)
 {
 }
 
-extern int smp_reinit_ipl_cpu(void);
 extern int smp_rescan_cpus(void);
 extern void __noreturn cpu_die(void);
 extern void __cpu_die(unsigned int cpu);

arch/s390/kernel/setup.c

@@ -381,12 +381,6 @@ void stack_free(unsigned long stack)
 #endif
 }
 
-void __init __noreturn arch_call_rest_init(void)
-{
-	smp_reinit_ipl_cpu();
-	rest_init();
-}
-
 static unsigned long __init stack_alloc_early(void)
 {
 	unsigned long stack;

arch/s390/kernel/smp.c

@@ -1256,60 +1256,3 @@ static int __init s390_smp_init(void)
 	return rc;
 }
 subsys_initcall(s390_smp_init);
-
-static __always_inline void set_new_lowcore(struct lowcore *lc)
-{
-	union register_pair dst, src;
-	u32 pfx;
-
-	src.even = (unsigned long) &S390_lowcore;
-	src.odd  = sizeof(S390_lowcore);
-	dst.even = (unsigned long) lc;
-	dst.odd  = sizeof(*lc);
-	pfx = __pa(lc);
-
-	asm volatile(
-		"	mvcl	%[dst],%[src]\n"
-		"	spx	%[pfx]\n"
-		: [dst] "+&d" (dst.pair), [src] "+&d" (src.pair)
-		: [pfx] "Q" (pfx)
-		: "memory", "cc");
-}
-
-int __init smp_reinit_ipl_cpu(void)
-{
-	unsigned long async_stack, nodat_stack, mcck_stack;
-	struct lowcore *lc, *lc_ipl;
-	unsigned long flags, cr0;
-	u64 mcesad;
-
-	lc_ipl = lowcore_ptr[0];
-	lc = (struct lowcore *)	__get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);
-	nodat_stack = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER);
-	async_stack = stack_alloc();
-	mcck_stack = stack_alloc();
-	if (!lc || !nodat_stack || !async_stack || !mcck_stack || nmi_alloc_mcesa(&mcesad))
-		panic("Couldn't allocate memory");
-
-	local_irq_save(flags);
-	local_mcck_disable();
-	set_new_lowcore(lc);
-	S390_lowcore.nodat_stack = nodat_stack + STACK_INIT_OFFSET;
-	S390_lowcore.async_stack = async_stack + STACK_INIT_OFFSET;
-	S390_lowcore.mcck_stack = mcck_stack + STACK_INIT_OFFSET;
-	__ctl_store(cr0, 0, 0);
-	__ctl_clear_bit(0, 28); /* disable lowcore protection */
-	S390_lowcore.mcesad = mcesad;
-	__ctl_load(cr0, 0, 0);
-	if (abs_lowcore_map(0, lc, false))
-		panic("Couldn't remap absolute lowcore");
-	lowcore_ptr[0] = lc;
-	local_mcck_enable();
-	local_irq_restore(flags);
-
-	memblock_free_late(__pa(lc_ipl->mcck_stack - STACK_INIT_OFFSET), THREAD_SIZE);
-	memblock_free_late(__pa(lc_ipl->async_stack - STACK_INIT_OFFSET), THREAD_SIZE);
-	memblock_free_late(__pa(lc_ipl->nodat_stack - STACK_INIT_OFFSET), THREAD_SIZE);
-	memblock_free_late(__pa(lc_ipl), sizeof(*lc_ipl));
-	return 0;
-}