diff --git a/include/boot/linux_layout.h b/include/boot/linux_layout.h
index 5ed2e476..f8b6563c 100644
--- a/include/boot/linux_layout.h
+++ b/include/boot/linux_layout.h
@@ -23,6 +23,7 @@
 #define INITRD_SIZE		_AC(0x10410, UL)
 #define OLDMEM_BASE		_AC(0x10418, UL)
 #define OLDMEM_SIZE		_AC(0x10420, UL)
+#define MAX_COMMAND_LINE_SIZE	_AC(0x10430, UL)
 #define COMMAND_LINE		_AC(0x10480, UL)
 
 /* Parameter sizes */
diff --git a/zipl/boot/stage3.c b/zipl/boot/stage3.c
index 7372fd64..428cc28c 100644
--- a/zipl/boot/stage3.c
+++ b/zipl/boot/stage3.c
@@ -232,7 +232,8 @@ static void parse_envblk(struct env_hash_entry *items,
  * CMDL_LEN: length of the command line to be processed
  * BUCKETS: hash table of pairs (NAME, VALUE)
  */
-void process_parm_line(struct env_hash_entry **buckets, unsigned int cmdl_len)
+void process_parm_line(struct env_hash_entry **buckets, unsigned int cmdl_len,
+		       unsigned int max_len)
 {
 	struct env_hash_entry *item;
 	char empty_str = 0;
@@ -282,7 +283,7 @@ void process_parm_line(struct env_hash_entry **buckets, unsigned int cmdl_len)
 		 */
 		len = strlen(val);
 
-		if (cmdl_len + len - (end - start + 1) >= LEGACY_COMMAND_LINE_SIZE)
+		if (cmdl_len + len - (end - start + 1) >= max_len)
 			/* VALUE doesn't fit */
 			break;
 		/*
@@ -306,7 +307,7 @@ void process_parm_line(struct env_hash_entry **buckets, unsigned int cmdl_len)
 /**
  * LEN: length of the command line to be processed
  */
-static void handle_environment(unsigned int len)
+static void handle_environment(unsigned int len, unsigned int max_len)
 {
 	struct env_hash_entry *buckets[STR_HASH_SIZE];
 	struct env_hash_entry *items;
@@ -326,7 +327,7 @@ static void handle_environment(unsigned int len)
 	 * find environment variables in the command line and
 	 * replace them with their values as found in the hash table
 	 */
-	process_parm_line(buckets, len);
+	process_parm_line(buckets, len, max_len);
 	free_page((unsigned long)items);
 }
 
@@ -350,14 +351,18 @@ static void setup_cmdline(void)
 	char *cextra = (char *)COMMAND_LINE_EXTRA;
 	char *cmdline =  (char *)COMMAND_LINE;
 	unsigned int cmdline_len = 0;
+	unsigned int max_cmdline_len = *(unsigned long *)MAX_COMMAND_LINE_SIZE;
+
+	if (!max_cmdline_len)
+		max_cmdline_len = LEGACY_COMMAND_LINE_SIZE;
 
 	/* if valid command line is given, copy it into new kernel space */
 	if (_stage3_parms.parm_addr != UNSPECIFIED_ADDRESS) {
 		strlcpy(cmdline, (void *)(unsigned long *)_stage3_parms.parm_addr,
-		       LEGACY_COMMAND_LINE_SIZE);
+		       max_cmdline_len);
 	}
 	/* determine length of original parm line */
-	cmdline_len = MIN(strlen(cmdline), LEGACY_COMMAND_LINE_SIZE - 1);
+	cmdline_len = MIN((unsigned int)strlen(cmdline), max_cmdline_len - 1);
 
 	/* convert extra parameter to ascii */
 	if (!_stage3_parms.extra_parm || !*cextra)
@@ -374,15 +379,15 @@ static void setup_cmdline(void)
 	 * else append
 	 */
 	if (*cextra == 0x3d) {
-		strlcpy(cmdline, cextra+1, LEGACY_COMMAND_LINE_SIZE);
-	} else if (*cextra && cmdline_len + 1 <= LEGACY_COMMAND_LINE_SIZE - 1) {
+		strlcpy(cmdline, cextra+1, max_cmdline_len);
+	} else if (*cextra && cmdline_len + 1 <= max_cmdline_len - 1) {
 		/* add blank */
 		cmdline[cmdline_len++] = 0x20;
-		strlcpy(cmdline + cmdline_len, cextra, LEGACY_COMMAND_LINE_SIZE - cmdline_len);
+		strlcpy(cmdline + cmdline_len, cextra, max_cmdline_len - cmdline_len);
 	}
 
 noextra:
-	handle_environment(strlen(cmdline));
+	handle_environment(strlen(cmdline), max_cmdline_len);
 }
 
 void start(void)
diff --git a/zipl/boot/tape0.S b/zipl/boot/tape0.S
index e4f04a39..c42d3b91 100644
--- a/zipl/boot/tape0.S
+++ b/zipl/boot/tape0.S
@@ -249,31 +249,35 @@ iplstart:
 	clc   0(3,%r4),.L_eof			# if it is EOFx
 	bz    .Lagain1				# skip dateset trailer
 
-	chi   %r2,LEGACY_COMMAND_LINE_SIZE-1	# truncate if line too long
+	lt    %r3,MAX_COMMAND_LINE_SIZE-PARMAREA+4(%r12)
+	jnz   0f
+	lhi   %r3,LEGACY_COMMAND_LINE_SIZE
+0:	cr    %r2,%r3				# truncate if line too long
 	bnh   .Lnotrunc
-	la    %r2,LEGACY_COMMAND_LINE_SIZE-1
+	lr    %r2,%r3
 .Lnotrunc:
-
 	la    %r5,0(%r4,%r2)			# search for EBCDIC chars
-	lr    %r3,%r2
+	ahi   %r5,-1
+	lr    %r6,%r2
 .Lidebc:
 	tm    0(%r5),0x80			# high order bit set ?
 	bo    .Ldocv				#  yes -> convert from EBCDIC
 	ahi   %r5,-1
-	bct   %r3,.Lidebc
+	bct   %r6,.Lidebc
 	b     .Lnocv
 .Ldocv:
-	la    %r3,_ebcasc
-	tr    0(256,%r4),0(%r3)			# convert parameters to ascii
-	tr    256(256,%r4),0(%r3)
-	tr    512(256,%r4),0(%r3)
-	tr    768(127,%r4),0(%r3)
+	lr    %r6,%r2
+	la    %r5,_ebcasc
+0:	tr    0(1,%r4),0(%r5)
+	ahi   %r4,1
+	brct  %r6,0b
+	l     %r4,_parm_addr+4
 .Lnocv:
-	la    %r3,COMMAND_LINE-PARMAREA(%r12)	# load adr. of command line
-	mvc   0(256,%r3),0(%r4)
-	mvc   256(256,%r3),256(%r4)
-	mvc   512(256,%r3),512(%r4)
-	mvc   768(127,%r3),768(%r4)
+	lr    %r5,%r2
+	ahi   %r5,-1
+	la    %r6,COMMAND_LINE-PARMAREA(%r12)
+	lr    %r7,%r2
+	mvcl  %r6,%r4
 	slr   %r0,%r0
 	b     .Lcntlp
 .Ldelspc: