s390/kdump: Use real mode for PSW restart and kexec

Currently the PSW restart handler and kexec are executed in real
mode with DAT=off. For kexec/kdump the function setup_regs() is
called that uses the per-cpu variable "crash_notes". Because
there are situations when the per-cpu implementation uses vmalloc
memory, calling setup_regs() in real mode can cause a program
check interrupt.

To fix that problem this patch changes the following:

* Ensure that diag308_reset() does not change PSW bits to real mode
* Enable DAT in __do_restart() after we switched to an online CPU
* Enable DAT in __machine_kexec() after we switched to the IPL CPU
* Call setup_regs() before we switch to real mode and call purgatory

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/s390/kernel/base.S b/arch/s390/kernel/base.S
index 3aa4d00aaf50..c880ff72db44 100644
--- a/arch/s390/kernel/base.S
+++ b/arch/s390/kernel/base.S
@@ -88,6 +88,9 @@ ENTRY(diag308_reset)
         stctg   %c0,%c15,0(%r4)
         larl    %r4,.Lfpctl             # Floating point control register
         stfpc   0(%r4)
+        larl    %r4,.Lcontinue_psw      # Save PSW flags
+        epsw    %r2,%r3
+        stm     %r2,%r3,0(%r4)
         larl    %r4,.Lrestart_psw       # Setup restart PSW at absolute 0
         lghi    %r3,0
         lg      %r4,0(%r4)              # Save PSW
@@ -103,11 +106,20 @@ ENTRY(diag308_reset)
         lctlg   %c0,%c15,0(%r4)
         larl    %r4,.Lfpctl             # Restore floating point ctl register
         lfpc    0(%r4)
+        larl    %r4,.Lcontinue_psw      # Restore PSW flags
+        lpswe   0(%r4)
+.Lcontinue:
         br      %r14
 .align 16
 .Lrestart_psw:
         .long   0x00080000,0x80000000 + .Lrestart_part2
 
+        .section .data..nosave,"aw",@progbits
+.align 8
+.Lcontinue_psw:
+        .quad   0,.Lcontinue
+        .previous
+
         .section .bss
 .align 8
 .Lctlregs: