diff options
| author | Thomas Gleixner <tglx@kernel.org> | 2026-02-24 19:36:49 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-02-27 18:40:09 +0300 |
| commit | f246ec3478cfdab830ee0815209f48923e7ee5e2 (patch) | |
| tree | 27baa4e3b762a4d86965c2eae68a76190105a8bf | |
| parent | 89f951a1e8ad781e7ac70eccddab0e0c270485f9 (diff) | |
| download | linux-f246ec3478cfdab830ee0815209f48923e7ee5e2.tar.xz | |
x86/apic: Enable TSC coupled programming mode
The TSC deadline timer is directly coupled to the TSC and setting the next
deadline is tedious as the clockevents core code converts the
CLOCK_MONOTONIC based absolute expiry time to a relative expiry by reading
the current time from the TSC. It converts that delta to cycles and hands
the result to lapic_next_deadline(), which then has read to the TSC and add
the delta to program the timer.
The core code now supports coupled clock event devices and can provide the
expiry time in TSC cycles directly without reading the TSC at all.
This obviouly works only when the TSC is the current clocksource, but
that's the default for all modern CPUs which implement the TSC deadline
timer. If the TSC is not the current clocksource (e.g. early boot) then the
core code falls back to the relative set_next_event() callback as before.
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260224163430.076565985@kernel.org
| -rw-r--r-- | arch/x86/Kconfig | 1 | ||||
| -rw-r--r-- | arch/x86/include/asm/clock_inlined.h | 8 | ||||
| -rw-r--r-- | arch/x86/kernel/apic/apic.c | 12 | ||||
| -rw-r--r-- | arch/x86/kernel/tsc.c | 3 |
4 files changed, 17 insertions, 7 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index d337d8dced86..560d2ce8cedd 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -164,6 +164,7 @@ config X86 select EDAC_SUPPORT select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC) select GENERIC_CLOCKEVENTS_BROADCAST_IDLE if GENERIC_CLOCKEVENTS_BROADCAST + select GENERIC_CLOCKEVENTS_COUPLED_INLINE if X86_64 select GENERIC_CLOCKEVENTS_MIN_ADJUST select GENERIC_CMOS_UPDATE select GENERIC_CPU_AUTOPROBE diff --git a/arch/x86/include/asm/clock_inlined.h b/arch/x86/include/asm/clock_inlined.h index 29902c5bcc5c..b2dee8db2fb9 100644 --- a/arch/x86/include/asm/clock_inlined.h +++ b/arch/x86/include/asm/clock_inlined.h @@ -11,4 +11,12 @@ static __always_inline u64 arch_inlined_clocksource_read(struct clocksource *cs) return (u64)rdtsc_ordered(); } +struct clock_event_device; + +static __always_inline void +arch_inlined_clockevent_set_next_coupled(u64 cycles, struct clock_event_device *evt) +{ + native_wrmsrq(MSR_IA32_TSC_DEADLINE, cycles); +} + #endif diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 5bb5b39376ca..60cab20b7901 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -591,14 +591,14 @@ static void setup_APIC_timer(void) if (this_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER)) { levt->name = "lapic-deadline"; - levt->features &= ~(CLOCK_EVT_FEAT_PERIODIC | - CLOCK_EVT_FEAT_DUMMY); + levt->features &= ~(CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_DUMMY); + levt->features |= CLOCK_EVT_FEAT_CLOCKSOURCE_COUPLED; + levt->cs_id = CSID_X86_TSC; levt->set_next_event = lapic_next_deadline; - clockevents_config_and_register(levt, - tsc_khz * (1000 / TSC_DIVISOR), - 0xF, ~0UL); - } else + clockevents_config_and_register(levt, tsc_khz * (1000 / TSC_DIVISOR), 0xF, ~0UL); + } else { clockevents_register_device(levt); + } apic_update_vector(smp_processor_id(), LOCAL_TIMER_VECTOR, true); } diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 74a26fb4417c..f31046f98a92 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1203,7 +1203,8 @@ static struct clocksource clocksource_tsc = { CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_CAN_INLINE_READ | CLOCK_SOURCE_MUST_VERIFY | - CLOCK_SOURCE_VERIFY_PERCPU, + CLOCK_SOURCE_VERIFY_PERCPU | + CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT, .id = CSID_X86_TSC, .vdso_clock_mode = VDSO_CLOCKMODE_TSC, .enable = tsc_cs_enable, |