Revert "UBUNTU: SAUCE: s390: improve cpu alternative handling for gmb and nobp"

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

This reverts commit a9a979ca to be
replaced by the upstream patch set from 4.4.130.
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/s390/Kconfig

@@ -483,23 +483,6 @@ source kernel/Kconfig.preempt
 
 source kernel/Kconfig.hz
 
-config KERNEL_NOBP
-       def_bool n
-       prompt "Enable modified branch prediction for the kernel by default"
-       help
-         If this option is selected the kernel will switch to a modified
-	 branch prediction mode if the firmware interface is available.
-	 The modified branch prediction mode improves the behaviour in
-	 regard to speculative execution.
-
-	 With the option enabled the kernel parameter "nobp=0" or "nospec"
-	 can be used to run the kernel in the normal branch prediction mode.
-
-	 With the option disabled the modified branch prediction mode is
-	 enabled with the "nobp=1" kernel parameter.
-
-	 If unsure, say N.
-
 endmenu
 
 menu "Memory setup"

arch/s390/include/asm/facility.h

@@ -13,24 +13,6 @@
 
 #define MAX_FACILITY_BIT (256*8)	/* stfle_fac_list has 256 bytes */
 
-static inline void __set_facility(unsigned long nr, void *facilities)
-{
-	unsigned char *ptr = (unsigned char *) facilities;
-
-	if (nr >= MAX_FACILITY_BIT)
-		return;
-	ptr[nr >> 3] |= 0x80 >> (nr & 7);
-}
-
-static inline void __clear_facility(unsigned long nr, void *facilities)
-{
-	unsigned char *ptr = (unsigned char *) facilities;
-
-	if (nr >= MAX_FACILITY_BIT)
-		return;
-	ptr[nr >> 3] &= ~(0x80 >> (nr & 7));
-}
-
 static inline int __test_facility(unsigned long nr, void *facilities)
 {
 	unsigned char *ptr;

arch/s390/include/asm/lowcore.h

@@ -170,8 +170,7 @@ struct _lowcore {
 	__u8	pad_0x0e20[0x0f00-0x0e20];	/* 0x0e20 */
 
 	/* Extended facility list */
-	__u64	stfle_fac_list[16];		/* 0x0f00 */
-	__u64	alt_stfle_fac_list[16];		/* 0x0f80 */
+	__u64	stfle_fac_list[32];		/* 0x0f00 */
 	__u8	pad_0x1000[0x11b0-0x1000];	/* 0x1000 */
 
 	/* Pointer to vector register save area */

arch/s390/kernel/alternative.c

@@ -14,35 +14,18 @@ static int __init disable_alternative_instructions(char *str)
 
 early_param("noaltinstr", disable_alternative_instructions);
 
-static int __init nobp_setup_early(char *str)
+extern struct alt_instr __alt_nobp[], __alt_nobp_end[];
+static int __init nobp_setup(char *str)
 {
 	bool enabled;
 	int rc;
 
 	rc = strtobool(str, &enabled);
-	if (rc)
+	if (!rc && enabled)
+		apply_alternatives(__alt_nobp, __alt_nobp_end);
 	return rc;
-	if (enabled && test_facility(82))
-		__set_facility(82, S390_lowcore.alt_stfle_fac_list);
-	else
-		__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
-	return 0;
-}
-early_param("nobp", nobp_setup_early);
-
-static int __init nospec_setup_early(char *str)
-{
-	__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
-	return 0;
-}
-early_param("nospec", nospec_setup_early);
-
-static int __init nogmb_setup_early(char *str)
-{
-	__clear_facility(81, S390_lowcore.alt_stfle_fac_list);
-	return 0;
 }
-early_param("nogmb", nogmb_setup_early);
+__setup("nobp=", nobp_setup);
 
 struct brcl_insn {
 	u16 opc;
@@ -104,8 +87,7 @@ static void __init_or_module __apply_alternatives(struct alt_instr *start,
 		instr = (u8 *)&a->instr_offset + a->instr_offset;
 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 
-		if (!__test_facility(a->facility,
-				     S390_lowcore.alt_stfle_fac_list))
+		if (!test_facility(a->facility))
 			continue;
 
 		if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {

arch/s390/kernel/early.c

@@ -279,11 +279,6 @@ static noinline __init void setup_facility_list(void)
 {
 	stfle(S390_lowcore.stfle_fac_list,
 	      ARRAY_SIZE(S390_lowcore.stfle_fac_list));
-	memcpy(S390_lowcore.alt_stfle_fac_list,
-	       S390_lowcore.stfle_fac_list,
-	       sizeof(S390_lowcore.alt_stfle_fac_list));
-	if (!IS_ENABLED(CONFIG_KERNEL_NOBP))
-		__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
 }
 
 static __init void detect_diag9c(void)

arch/s390/kernel/entry.S

@@ -167,7 +167,7 @@ _PIF_WORK	= (_PIF_PER_TRAP)
 660:	.long	0xb2e8c000
 	.popsection
 661:	.long	0x47000000
-	.pushsection .altinstructions, "a"
+	.pushsection .altnobp, "a"
 	.long 661b - .
 	.long 660b - .
 	.word 82
@@ -181,7 +181,7 @@ _PIF_WORK	= (_PIF_PER_TRAP)
 662:	.long	0xb2e8d000
 	.popsection
 663:	.long	0x47000000
-	.pushsection .altinstructions, "a"
+	.pushsection .altnobp, "a"
 	.long 663b - .
 	.long 662b - .
 	.word 82

arch/s390/kernel/setup.c

@@ -334,9 +334,7 @@ static void __init setup_lowcore(void)
 	lc->machine_flags = S390_lowcore.machine_flags;
 	lc->stfl_fac_list = S390_lowcore.stfl_fac_list;
 	memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
-	       sizeof(lc->stfle_fac_list));
-	memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
-	       sizeof(lc->alt_stfle_fac_list));
+	       MAX_FACILITY_BIT/8);
 	if (MACHINE_HAS_VX)
 		lc->vector_save_area_addr =
 			(unsigned long) &lc->vector_save_area;

arch/s390/kernel/smp.c

@@ -250,9 +250,7 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
 	__ctl_store(lc->cregs_save_area, 0, 15);
 	save_access_regs((unsigned int *) lc->access_regs_save_area);
 	memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
-	       sizeof(lc->stfle_fac_list));
-	memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
-	       sizeof(lc->alt_stfle_fac_list));
+	       MAX_FACILITY_BIT/8);
 }
 
 static void pcpu_attach_task(struct pcpu *pcpu, struct task_struct *tsk)

arch/s390/kernel/vmlinux.lds.S

@@ -89,6 +89,9 @@ SECTIONS
 		__alt_instructions = .;
 		*(.altinstructions)
 		__alt_instructions_end = .;
+		__alt_nobp = .;
+		*(.altnobp)
+		__alt_nobp_end = .;
 	}
 
 	/*