s390/boot: Defer boot messages when earlyprintk is not enabled

When earlyprintk is not specified, boot messages are only stored in a
ring buffer to be printed later by printk when console driver is
registered.

Critical messages from boot_emerg() are always printed immediately,
even without earlyprintk.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/boot/ipl_parm.c

@@ -313,6 +313,8 @@ void parse_boot_command_line(void)
 #endif
 		if (!strcmp(param, "relocate_lowcore") && test_facility(193))
 			relocate_lowcore = 1;
+		if (!strcmp(param, "earlyprintk"))
+			boot_earlyprintk = true;
 		if (!strcmp(param, "debug"))
 			boot_console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
 		if (!strcmp(param, "quiet"))

arch/s390/boot/printk.c

@@ -5,6 +5,7 @@
 #include <linux/ctype.h>
 #include <asm/stacktrace.h>
 #include <asm/boot_data.h>
+#include <asm/sections.h>
 #include <asm/lowcore.h>
 #include <asm/setup.h>
 #include <asm/sclp.h>
@@ -13,8 +14,9 @@
 
 int boot_console_loglevel = CONFIG_CONSOLE_LOGLEVEL_DEFAULT;
 bool boot_ignore_loglevel;
-char boot_rb[PAGE_SIZE * 2];
-size_t boot_rb_off;
+char __bootdata(boot_rb)[PAGE_SIZE * 2];
+bool __bootdata(boot_earlyprintk);
+size_t __bootdata(boot_rb_off);
 
 static void boot_rb_add(const char *str, size_t len)
 {
@@ -163,6 +165,9 @@ static void boot_console_earlyprintk(const char *buf)
 {
 	int level = printk_loglevel(buf);
 
+	/* always print emergency messages */
+	if (level > LOGLEVEL_EMERG && !boot_earlyprintk)
+		return;
 	if (boot_ignore_loglevel || level < boot_console_loglevel)
 		sclp_early_printk(printk_skip_level(buf));
 }

arch/s390/include/asm/boot_data.h

@@ -16,6 +16,7 @@ extern unsigned long early_ipl_comp_list_addr;
 extern unsigned long early_ipl_comp_list_size;
 
 extern char boot_rb[PAGE_SIZE * 2];
+extern bool boot_earlyprintk;
 extern size_t boot_rb_off;
 
 #define boot_rb_foreach(cb)							\

arch/s390/kernel/setup.c

@@ -157,6 +157,10 @@ u64 __bootdata_preserved(stfle_fac_list[16]);
 EXPORT_SYMBOL(stfle_fac_list);
 struct oldmem_data __bootdata_preserved(oldmem_data);
 
+char __bootdata(boot_rb)[PAGE_SIZE * 2];
+bool __bootdata(boot_earlyprintk);
+size_t __bootdata(boot_rb_off);
+
 unsigned long __bootdata_preserved(VMALLOC_START);
 EXPORT_SYMBOL(VMALLOC_START);
 
@@ -877,6 +881,17 @@ static void __init log_component_list(void)
 	}
 }
 
+/*
+ * Print avoiding interpretation of % in buf
+ */
+static void __init print_rb_entry(char *buf)
+{
+	char fmt[] = KERN_SOH "0boot: %s";
+
+	fmt[1] = printk_get_level(buf);
+	printk(fmt, printk_skip_level(buf));
+}
+
 /*
  * Setup function called from init/main.c just after the banner
  * was printed.
@@ -896,6 +911,9 @@ void __init setup_arch(char **cmdline_p)
 		pr_info("Linux is running natively in 64-bit mode\n");
 	else
 		pr_info("Linux is running as a guest in 64-bit mode\n");
+	/* Print decompressor messages if not already printed */
+	if (!boot_earlyprintk)
+		boot_rb_foreach(print_rb_entry);
 
 	if (have_relocated_lowcore())
 		pr_info("Lowcore relocated to 0x%px\n", get_lowcore());