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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
23 lines
465 B
C
23 lines
465 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_CLOCK_INLINED_H
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#define _ASM_X86_CLOCK_INLINED_H
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#include <asm/tsc.h>
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struct clocksource;
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static __always_inline u64 arch_inlined_clocksource_read(struct clocksource *cs)
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{
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return (u64)rdtsc_ordered();
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}
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struct clock_event_device;
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static __always_inline void
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arch_inlined_clockevent_set_next_coupled(u64 cycles, struct clock_event_device *evt)
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{
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native_wrmsrq(MSR_IA32_TSC_DEADLINE, cycles);
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}
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#endif
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