[S390] Fix reboot hang on LPARs

Reboot hangs on LPARs without diag308 support. The reason for this is,
that before the reboot is done, the channel subsystem is shut down.
During the reset on each possible subchannel a "store subchannel" is
done. This operation can end in a program check interruption, if the
specified subchannel set is not implemented by the hardware. During
the reset, currently we do not have a program check handler, which
leads to the described kernel bug. We install now a new program check
handler for the reboot code to fix this problem.

Signed-off-by: Michael Holzheu <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/kernel/ipl.c

···
 }
 
 extern void reset_mcck_handler(void);
+extern void reset_pgm_handler(void);
 
 void s390_reset_system(void)
 {
 	struct _lowcore *lc;
 
-	/* Stack for interrupt/machine check handler */
 	lc = (struct _lowcore *)(unsigned long) store_prefix();
+
+	/* Stack for interrupt/machine check handler */
 	lc->panic_stack = S390_lowcore.panic_stack;
 
 	/* Disable prefixing */
···
 	S390_lowcore.mcck_new_psw.mask = PSW_KERNEL_BITS & ~PSW_MASK_MCHECK;
 	S390_lowcore.mcck_new_psw.addr =
 		PSW_ADDR_AMODE | (unsigned long) &reset_mcck_handler;
+
+	/* Set new program check handler */
+	S390_lowcore.program_new_psw.mask = PSW_KERNEL_BITS & ~PSW_MASK_MCHECK;
+	S390_lowcore.program_new_psw.addr =
+		PSW_ADDR_AMODE | (unsigned long) &reset_pgm_handler;
+
 	do_reset_calls();
 }

arch/s390/kernel/reset.S

···
  *
  *    Copyright (C) IBM Corp. 2006
  *    Author(s): Heiko Carstens <[e-mail]>
+ *		 Michael Holzheu <[e-mail]>
  */
 
 #include <asm/ptrace.h>
···
 s390_reset_mcck_handler:
 	.quad	0
 
+	.globl	reset_pgm_handler
+reset_pgm_handler:
+	stmg	%r0,%r15,__LC_SAVE_AREA
+	basr	%r13,0
+0:	lg	%r15,__LC_PANIC_STACK	# load panic stack
+	aghi	%r15,-STACK_FRAME_OVERHEAD
+	lg	%r1,s390_reset_pgm_handler-0b(%r13)
+	ltgr	%r1,%r1
+	jz	1f
+	basr	%r14,%r1
+	lmg	%r0,%r15,__LC_SAVE_AREA
+	lpswe	__LC_PGM_OLD_PSW
+1:	lpswe	disabled_wait_psw-0b(%r13)
+	.globl s390_reset_pgm_handler
+s390_reset_pgm_handler:
+	.quad	0
+	.align	8
+disabled_wait_psw:
+	.quad	0x0002000180000000,0x0000000000000000 + reset_pgm_handler
+
 #else /* CONFIG_64BIT */
 
 	.globl	reset_mcck_handler
···
 	.globl	s390_reset_mcck_handler
 s390_reset_mcck_handler:
 	.long	0
+
+	.globl	reset_pgm_handler
+reset_pgm_handler:
+	stm	%r0,%r15,__LC_SAVE_AREA
+	basr	%r13,0
+0:	l	%r15,__LC_PANIC_STACK	# load panic stack
+	ahi	%r15,-STACK_FRAME_OVERHEAD
+	l	%r1,s390_reset_pgm_handler-0b(%r13)
+	ltr	%r1,%r1
+	jz	1f
+	basr	%r14,%r1
+	lm	%r0,%r15,__LC_SAVE_AREA
+	lpsw	__LC_PGM_OLD_PSW
+
+1:	lpsw	disabled_wait_psw-0b(%r13)
+	.globl	s390_reset_pgm_handler
+s390_reset_pgm_handler:
+	.long	0
+disabled_wait_psw:
+	.align 8
+	.long	0x000a0000,0x00000000 + reset_pgm_handler
 
 #endif /* CONFIG_64BIT */

drivers/s390/cio/cio.c

···
 	return -EBUSY;
 }
 
+static int pgm_check_occured;
+
+static void cio_reset_pgm_check_handler(void)
+{
+	pgm_check_occured = 1;
+}
+
+static int stsch_reset(struct subchannel_id schid, volatile struct schib *addr)
+{
+	int rc;
+
+	pgm_check_occured = 0;
+	s390_reset_pgm_handler = cio_reset_pgm_check_handler;
+	rc = stsch(schid, addr);
+	s390_reset_pgm_handler = NULL;
+	if (pgm_check_occured)
+		return -EIO;
+	else
+		return rc;
+}
+
 static int __shutdown_subchannel_easy(struct subchannel_id schid, void *data)
 {
 	struct schib schib;
 
-	if (stsch_err(schid, &schib))
+	if (stsch_reset(schid, &schib))
 		return -ENXIO;
 	if (!schib.pmcw.ena)
 		return 0;
···
 	struct schib schib;
 	struct sch_match_id *match_id = data;
 
-	if (stsch_err(schid, &schib))
+	if (stsch_reset(schid, &schib))
 		return -ENXIO;
 	if (schib.pmcw.dnv &&
 	    (schib.pmcw.dev == match_id->devid.devno) &&

include/asm-s390/reset.h

···
 extern void unregister_reset_call(struct reset_call *reset);
 extern void s390_reset_system(void);
 extern void (*s390_reset_mcck_handler)(void);
+extern void (*s390_reset_pgm_handler)(void);
 
 #endif /* _ASM_S390_RESET_H */