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>

3 files changed, 15 insertions, 1 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:
diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 8342e65a140d..dcfdcb3ea163 100644
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -1750,6 +1750,7 @@ static struct kobj_attribute on_restart_attr =
 
 static void __do_restart(void *ignore)
 {
+        __arch_local_irq_stosm(0x04); /* enable DAT */
         smp_send_stop();
 #ifdef CONFIG_CRASH_DUMP
         crash_kexec(NULL);
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index 03d2027d656a..cdacf8f91b2d 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -80,8 +80,8 @@ static void __do_machine_kdump(void *image)
 #ifdef CONFIG_CRASH_DUMP
         int (*start_kdump)(int) = (void *)((struct kimage *) image)->start;
 
-        __load_psw_mask(PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA);
         setup_regs();
+        __load_psw_mask(PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA);
         start_kdump(1);
 #endif
 }
@@ -214,6 +214,7 @@ static void __machine_kexec(void *data)
 {
         struct kimage *image = data;
 
+        __arch_local_irq_stosm(0x04); /* enable DAT */
         pfault_fini();
         tracing_off();
         debug_locks_off();