s390/module: enable generic CPU feature modalias using s390 ELF hwcaps

Add support for the generic CPU feature modalias implementation that wires
up optional CPU features to udev-based module autoprobing.

The <asm/cpufeature.h> file provides definitions to map CPU features to
s390 ELF hardware capabilities.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -105,6 +105,7 @@ config S390
 	select CLONE_BACKWARDS2
 	select DYNAMIC_FTRACE if FUNCTION_TRACER
 	select GENERIC_CLOCKEVENTS
+	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_CPU_DEVICES if !SMP
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_SMP_IDLE_THREAD

arch/s390/include/asm/cpufeature.h

@@ -0,0 +1,29 @@
+/*
+ * Module interface for CPU features
+ *
+ * Copyright IBM Corp. 2015
+ * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+ */
+
+#ifndef __ASM_S390_CPUFEATURE_H
+#define __ASM_S390_CPUFEATURE_H
+
+#include <asm/elf.h>
+
+/* Hardware features on Linux on z Systems are indicated by facility bits that
+ * are mapped to the so-called machine flags.  Particular machine flags are
+ * then used to define ELF hardware capabilities; most notably hardware flags
+ * that are essential for user space / glibc.
+ *
+ * Restrict the set of exposed CPU features to ELF hardware capabilities for
+ * now.  Additional machine flags can be indicated by values larger than
+ * MAX_ELF_HWCAP_FEATURES.
+ */
+#define MAX_ELF_HWCAP_FEATURES	(8 * sizeof(elf_hwcap))
+#define MAX_CPU_FEATURES	MAX_ELF_HWCAP_FEATURES
+
+#define cpu_feature(feat)	ilog2(HWCAP_S390_ ## feat)
+
+int cpu_have_feature(unsigned int nr);
+
+#endif /* __ASM_S390_CPUFEATURE_H */

arch/s390/kernel/processor.c

@@ -40,6 +40,15 @@ void cpu_init(void)
 	enter_lazy_tlb(&init_mm, current);
 }
 
+/*
+ * cpu_have_feature - Test CPU features on module initialization
+ */
+int cpu_have_feature(unsigned int num)
+{
+	return elf_hwcap & (1UL << num);
+}
+EXPORT_SYMBOL(cpu_have_feature);
+
 /*
  * show_cpuinfo - Get information on one CPU for use by procfs.
  */

arch/s390/kernel/setup.c

@@ -76,7 +76,7 @@ EXPORT_SYMBOL(console_devno);
 unsigned int console_irq = -1;
 EXPORT_SYMBOL(console_irq);
 
-unsigned long elf_hwcap = 0;
+unsigned long elf_hwcap __read_mostly = 0;
 char elf_platform[ELF_PLATFORM_SIZE];
 
 int __initdata memory_end_set;