s390: enable CPU alternatives unconditionally

BugLink: http://bugs.launchpad.net/bugs/1768474

[ Upstream commit 049a2c2d ]

Remove the CPU_ALTERNATIVES config option and enable the code
unconditionally. The config option was only added to avoid a conflict
with the named saved segment support. Since that code is gone there is
no reason to keep the CPU_ALTERNATIVES config option.

Just enable it unconditionally to also reduce the number of config
options and make it less likely that something breaks.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/s390/Kconfig

@@ -705,22 +705,6 @@ config SECCOMP
 
 	  If unsure, say Y.
 
-config ALTERNATIVES
-	def_bool y
-	prompt "Patch optimized instructions for running CPU type"
-	help
-	  When enabled the kernel code is compiled with additional
-	  alternative instructions blocks optimized for newer CPU types.
-	  These alternative instructions blocks are patched at kernel boot
-	  time when running CPU supports them. This mechanism is used to
-	  optimize some critical code paths (i.e. spinlocks) for newer CPUs
-	  even if kernel is build to support older machine generations.
-
-	  This mechanism could be disabled by appending "noaltinstr"
-	  option to the kernel command line.
-
-	  If unsure, say Y.
-
 endmenu
 
 menu "Power Management"

arch/s390/include/asm/alternative.h

@@ -15,14 +15,9 @@ struct alt_instr {
 	u8  replacementlen;	/* length of new instruction */
 } __packed;
 
-#ifdef CONFIG_ALTERNATIVES
-extern void apply_alternative_instructions(void);
-extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
-#else
-static inline void apply_alternative_instructions(void) {};
-static inline void apply_alternatives(struct alt_instr *start,
-				      struct alt_instr *end) {};
-#endif
+void apply_alternative_instructions(void);
+void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+
 /*
  * |661:       |662:	  |6620      |663:
  * +-----------+---------------------+
@@ -109,7 +104,6 @@ static inline void apply_alternatives(struct alt_instr *start,
 	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"	\
 	INSTR_LEN_SANITY_CHECK(altinstr_len(num))
 
-#ifdef CONFIG_ALTERNATIVES
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, altinstr, facility) \
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
@@ -130,14 +124,6 @@ static inline void apply_alternatives(struct alt_instr *start,
 	ALTINSTR_ENTRY(facility1, 1)					\
 	ALTINSTR_ENTRY(facility2, 2)					\
 	".popsection\n"
-#else
-/* Alternative instructions are disabled, let's put just oldinstr in */
-#define ALTERNATIVE(oldinstr, altinstr, facility) \
-	oldinstr "\n"
-
-#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
-	oldinstr "\n"
-#endif
 
 /*
  * Alternative instructions for different CPU types or capabilities.

arch/s390/kernel/Makefile

@@ -44,7 +44,7 @@ obj-y	+= processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o diag.o sclp.o vdso.o
 obj-y	+= sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
 obj-y	+= runtime_instr.o cache.o dumpstack.o
-obj-y	+= entry.o reipl.o relocate_kernel.o
+obj-y	+= entry.o reipl.o relocate_kernel.o alternative.o
 
 extra-y				+= head.o head64.o vmlinux.lds
 
@@ -62,7 +62,6 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
-obj-$(CONFIG_ALTERNATIVES)	+= alternative.o
 
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf.o perf_cpum_sf.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf_events.o

arch/s390/kernel/module.c

@@ -428,16 +428,13 @@ int module_finalize(const Elf_Ehdr *hdr,
 	const Elf_Shdr *s;
 	char *secstrings;
 
-	if (IS_ENABLED(CONFIG_ALTERNATIVES)) {
-		secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
-		for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
-			if (!strcmp(".altinstructions",
-				    secstrings + s->sh_name)) {
-				/* patch .altinstructions */
-				void *aseg = (void *)s->sh_addr;
+	secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
+		if (!strcmp(".altinstructions", secstrings + s->sh_name)) {
+			/* patch .altinstructions */
+			void *aseg = (void *)s->sh_addr;
 
-				apply_alternatives(aseg, aseg + s->sh_size);
-			}
+			apply_alternatives(aseg, aseg + s->sh_size);
 		}
 	}