s390/als: print missing facilities on facility mismatch

If the kernel needs more facilities to run than the machine provides
it is running on, print the facility bit numbers which are missing.

This allows to easily tell what went wrong and if simply the machine
does not provide a required facility or if either the kernel or the
hypervisor may have a bug.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/als.c

@@ -44,10 +44,58 @@ static void __init print_machine_type(void)
 	_sclp_print_early(mach_str);
 }
 
+static void __init u16_to_decimal(char *str, u16 val)
+{
+	int div = 1;
+
+	while (div * 10 <= val)
+		div *= 10;
+	while (div) {
+		*str++ = '0' + val / div;
+		val %= div;
+		div /= 10;
+	}
+	*str = '\0';
+}
+
+static void __init print_missing_facilities(void)
+{
+	static char als_str[80] __initdata = "Missing facilities: ";
+	unsigned long val;
+	char val_str[6];
+	int i, j, first;
+
+	first = 1;
+	for (i = 0; i < ARRAY_SIZE(als); i++) {
+		val = ~S390_lowcore.stfle_fac_list[i] & als[i];
+		for (j = 0; j < BITS_PER_LONG; j++) {
+			if (!(val & (1UL << (BITS_PER_LONG - 1 - j))))
+				continue;
+			if (!first)
+				strcat(als_str, ",");
+			/*
+			 * Make sure we stay within one line. Consider that
+			 * each facility bit adds up to five characters and
+			 * z/VM adds a four character prefix.
+			 */
+			if (strlen(als_str) > 70) {
+				_sclp_print_early(als_str);
+				*als_str = '\0';
+			}
+			u16_to_decimal(val_str, i * BITS_PER_LONG + j);
+			strcat(als_str, val_str);
+			first = 0;
+		}
+	}
+	_sclp_print_early(als_str);
+	_sclp_print_early("See Principles of Operations for facility bits");
+}
+
 static void __init facility_mismatch(void)
 {
 	_sclp_print_early("The Linux kernel requires more recent processor hardware");
 	print_machine_type();
+	print_missing_facilities();
 	disabled_wait(0x8badcccc);
 }