s390/traps: Handle early warnings gracefully

Add missing warning handling to the early program check handler. This
way a warning is printed to the console as soon as the early console
is setup, and the kernel continues to boot.

Before this change a disabled wait psw was loaded instead and the
machine was silently stopped without giving an idea about what
happened.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/early.c

@@ -177,8 +177,21 @@ static __init void setup_topology(void)
 
 void __do_early_pgm_check(struct pt_regs *regs)
 {
-	if (!fixup_exception(regs))
-		disabled_wait();
+	struct lowcore *lc = get_lowcore();
+	unsigned long ip;
+
+	regs->int_code = lc->pgm_int_code;
+	regs->int_parm_long = lc->trans_exc_code;
+	ip = __rewind_psw(regs->psw, regs->int_code >> 16);
+
+	/* Monitor Event? Might be a warning */
+	if ((regs->int_code & PGM_INT_CODE_MASK) == 0x40) {
+		if (report_bug(ip, regs) == BUG_TRAP_TYPE_WARN)
+			return;
+	}
+	if (fixup_exception(regs))
+		return;
+	disabled_wait();
 }
 
 static noinline __init void setup_lowcore_early(void)