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s390/bp: remove __bpon()

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There is no point in changing branch prediction state of a cpu shortly
before it enters stop state. Therefore remove __bpon().

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-02-28 13:57:50 +01:00 committed by Vasily Gorbik
parent 9b63fd2fc8
commit 69a407bf81
4 changed files with 6 additions and 16 deletions
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1
arch/s390/include/asm/processor.h
View File

@ -99,7 +99,6 @@ void cpu_detect_mhz_feature(void);
extern const struct seq_operations cpuinfo_op;
extern void execve_tail(void);
extern void __bpon(void);
unsigned long vdso_size(void);
/*

18
arch/s390/kernel/entry.S
View File

@ -159,21 +159,15 @@ _LPP_OFFSET = __LC_LPP
.section .kprobes.text, "ax"
.Ldummy:
/*
* This nop exists only in order to avoid that __bpon starts at
* the beginning of the kprobes text section. In that case we would
* have several symbols at the same address. E.g. objdump would take
* an arbitrary symbol name when disassembling this code.
* With the added nop in between the __bpon symbol is unique
* again.
* The following nop exists only in order to avoid that the next
* symbol starts at the beginning of the kprobes text section.
* In that case there would be several symbols at the same address.
* E.g. objdump would take an arbitrary symbol when disassembling
* the code.
* With the added nop in between this cannot happen.
*/
nop 0
ENTRY(__bpon)
.globl __bpon
BPON
BR_EX %r14
ENDPROC(__bpon)
/*
* Scheduler resume function, called by switch_to
* gpr2 = (task_struct *) prev

1
arch/s390/kernel/ipl.c
View File

@ -649,7 +649,6 @@ static struct kset *ipl_kset;
static void __ipl_run(void *unused)
{
__bpon();
diag308(DIAG308_LOAD_CLEAR, NULL);
}

2
arch/s390/kernel/smp.c
View File

@ -348,7 +348,6 @@ static void pcpu_delegate(struct pcpu *pcpu,
abs_lc->restart_source = source_cpu;
put_abs_lowcore(abs_lc);
}
__bpon();
asm volatile(
"0: sigp 0,%0,%2 # sigp restart to target cpu\n"
" brc 2,0b # busy, try again\n"
@ -986,7 +985,6 @@ void __cpu_die(unsigned int cpu)
void __noreturn cpu_die(void)
{
idle_task_exit();
__bpon();
pcpu_sigp_retry(pcpu_devices + smp_processor_id(), SIGP_STOP, 0);
for (;;) ;
}