From: Martin Schwidefsky Date: Mon, 18 Feb 2019 18:10:08 +0100 Subject: s390/setup: fix boot crash for machine without EDAT-1 Git-commit: 86a86804e4f18fc3880541b3d5a07f4df0fe29cb Patch-mainline: v5.1-rc1 References: bsc#1051510 bsc#1140948 The fix to make WARN work in the early boot code created a problem on older machines without EDAT-1. The setup_lowcore_dat_on function uses the pointer from lowcore_ptr[0] to set the DAT bit in the new PSWs. That does not work if the kernel page table is set up with 4K pages as the prefix address maps to absolute zero. To make this work the PSWs need to be changed with via address 0 in form of the S390_lowcore definition. Reported-by: Guenter Roeck Tested-by: Cornelia Huck Fixes: 94f85ed3e2f8 ("s390/setup: fix early warning messages") Signed-off-by: Martin Schwidefsky Acked-by: Petr Tesarik --- arch/s390/kernel/setup.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -390,13 +390,12 @@ static void __init setup_lowcore_dat_off static void __init setup_lowcore_dat_on(void) { - struct lowcore *lc; - - lc = lowcore_ptr[0]; - lc->external_new_psw.mask |= PSW_MASK_DAT; - lc->svc_new_psw.mask |= PSW_MASK_DAT; - lc->program_new_psw.mask |= PSW_MASK_DAT; - lc->io_new_psw.mask |= PSW_MASK_DAT; + __ctl_clear_bit(0, 28); + S390_lowcore.external_new_psw.mask |= PSW_MASK_DAT; + S390_lowcore.svc_new_psw.mask |= PSW_MASK_DAT; + S390_lowcore.program_new_psw.mask |= PSW_MASK_DAT; + S390_lowcore.io_new_psw.mask |= PSW_MASK_DAT; + __ctl_set_bit(0, 28); } static struct resource code_resource = {