tree 9e8555cd1c95e817a6ffef6c9017d2b3b48c7241
parent e578f90d8a9cb6d4ae2e6cadc8aaab6e9a2aa656
author Martin Schwidefsky <schwidefsky@de.ibm.com> 1550509808 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1553368213 +0100

s390/setup: fix boot crash for machine without EDAT-1

commit 86a86804e4f18fc3880541b3d5a07f4df0fe29cb upstream.

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 <linux@roeck-us.net>
Tested-by: Cornelia Huck <cohuck@redhat.com>
Fixes: 94f85ed3e2f8 ("s390/setup: fix early warning messages")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>