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x86/cpu: Remove unused !CONFIG_X86_TSC code

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Now that the Kconfig space always enables CONFIG_X86_TSC (on x86),
remove !CONFIG_X86_TSC code from the x86 arch code.

We still keep the Kconfig option to catch any eventual code still
pending in maintainer or non-mainline trees, plus some drivers
have raw TSC timestamping hacks that use CONFIG_X86_TSC.

It's also still possible to disable TSC support runtime.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ahmed S . Darwish <darwi@linutronix.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250425084216.3913608-13-mingo@kernel.org
This commit is contained in:
Ingo Molnar 2026-04-27 08:07:02 +02:00
parent eabf869d79
commit 5c75b98aa9
6 changed files with 5 additions and 38 deletions
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3
arch/x86/include/asm/timex.h
View File

@ -7,8 +7,7 @@
static inline unsigned long random_get_entropy(void)
{
if (!IS_ENABLED(CONFIG_X86_TSC) &&
!cpu_feature_enabled(X86_FEATURE_TSC))
if (!cpu_feature_enabled(X86_FEATURE_TSC))
return random_get_entropy_fallback();
return rdtsc();
}

8
arch/x86/include/asm/trace_clock.h
View File

@ -5,17 +5,9 @@
#include <linux/compiler.h>
#include <linux/types.h>
#ifdef CONFIG_X86_TSC
extern u64 notrace trace_clock_x86_tsc(void);
# define ARCH_TRACE_CLOCKS \
{ trace_clock_x86_tsc, "x86-tsc", .in_ns = 0 },
#else /* !CONFIG_X86_TSC */
#define ARCH_TRACE_CLOCKS
#endif
#endif /* _ASM_X86_TRACE_CLOCK_H */

13
arch/x86/include/asm/tsc.h
View File

@ -76,8 +76,7 @@ extern void disable_TSC(void);
static inline cycles_t get_cycles(void)
{
if (!IS_ENABLED(CONFIG_X86_TSC) &&
!cpu_feature_enabled(X86_FEATURE_TSC))
if (!cpu_feature_enabled(X86_FEATURE_TSC))
return 0;
return rdtsc();
}
@ -94,25 +93,15 @@ extern unsigned long native_calibrate_tsc(void);
extern unsigned long long native_sched_clock_from_tsc(u64 tsc);
extern int tsc_clocksource_reliable;
#ifdef CONFIG_X86_TSC
extern bool tsc_async_resets;
#else
# define tsc_async_resets false
#endif
/*
* Boot-time check whether the TSCs are synchronized across
* all CPUs/cores:
*/
#ifdef CONFIG_X86_TSC
extern bool tsc_store_and_check_tsc_adjust(bool bootcpu);
extern void tsc_verify_tsc_adjust(bool resume);
extern void check_tsc_sync_target(void);
#else
static inline bool tsc_store_and_check_tsc_adjust(bool bootcpu) { return false; }
static inline void tsc_verify_tsc_adjust(bool resume) { }
static inline void check_tsc_sync_target(void) { }
#endif
extern int notsc_setup(char *);
extern void tsc_save_sched_clock_state(void);

4
arch/x86/kernel/Makefile
View File

@ -108,7 +108,7 @@ apm-y := apm_32.o
obj-$(CONFIG_APM) += apm.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SMP) += smpboot.o
obj-$(CONFIG_X86_TSC) += tsc_sync.o
obj-y += tsc_sync.o
obj-$(CONFIG_SMP) += setup_percpu.o
obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-y += apic/
@ -117,7 +117,7 @@ obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_FUNCTION_TRACER) += ftrace_$(BITS).o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
obj-$(CONFIG_X86_TSC) += trace_clock.o
obj-y += trace_clock.o
obj-$(CONFIG_TRACING) += trace.o
obj-$(CONFIG_RETHOOK) += rethook.o
obj-$(CONFIG_VMCORE_INFO) += vmcore_info_$(BITS).o

2
arch/x86/kernel/i8253.c
View File

@ -31,7 +31,7 @@ struct clock_event_device *global_clock_event;
*/
static bool __init use_pit(void)
{
if (!IS_ENABLED(CONFIG_X86_TSC) || !boot_cpu_has(X86_FEATURE_TSC))
if (!boot_cpu_has(X86_FEATURE_TSC))
return true;
/* This also returns true when APIC is disabled */

13
arch/x86/kernel/tsc.c
View File

@ -298,30 +298,17 @@ notrace u64 sched_clock(void)
preempt_enable_notrace();
return now;
}
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
#ifdef CONFIG_X86_TSC
int __init notsc_setup(char *str)
{
mark_tsc_unstable("boot parameter notsc");
return 1;
}
#else
/*
* disable flag for tsc. Takes effect by clearing the TSC cpu flag
* in cpu/common.c
*/
int __init notsc_setup(char *str)
{
setup_clear_cpu_cap(X86_FEATURE_TSC);
return 1;
}
#endif
__setup("notsc", notsc_setup);
enum {