s390/boot: fix absolute zero lowcore corruption on boot

[ Upstream commit 12dd19c ]

Crash dump always starts on CPU0. In case CPU0 is offline the
prefix page is not installed and the absolute zero lowcore is
used. However, struct lowcore::mcesad is never assigned and
stays zero. That leads to __machine_kdump() -> save_vx_regs()
call silently stores vector registers to the absolute lowcore
at 0x11b0 offset.

Fixes: a62bc07 ("s390/kdump: add support for vector extension")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/s390/kernel/nmi.c

@@ -62,7 +62,7 @@ static inline unsigned long nmi_get_mcesa_size(void)
  * The structure is required for machine check happening early in
  * the boot process.
  */
-static struct mcesa boot_mcesa __initdata __aligned(MCESA_MAX_SIZE);
+static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);
 
 void __init nmi_alloc_boot_cpu(struct lowcore *lc)
 {

arch/s390/kernel/setup.c

@@ -484,6 +484,7 @@ static void __init setup_lowcore_dat_off(void)
 	put_abs_lowcore(restart_data, lc->restart_data);
 	put_abs_lowcore(restart_source, lc->restart_source);
 	put_abs_lowcore(restart_psw, lc->restart_psw);
+	put_abs_lowcore(mcesad, lc->mcesad);
 
 	lc->spinlock_lockval = arch_spin_lockval(0);
 	lc->spinlock_index = 0;