内核提供了那些 kernel module 给虚拟机

内核的 hrtimer 和用户态的 timer 使用的是一个机制吧

描述从 从 clockid 到 hrtimer_bases 的变化:

/*
 * The timer bases:
 *
 * There are more clockids than hrtimer bases. Thus, we index
 * into the timer bases by the hrtimer_base_type enum. When trying
 * to reach a base using a clockid, hrtimer_clockid_to_base()
 * is used to convert from clockid to the proper hrtimer_base_type.
 */
DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =

enum  hrtimer_base_type {
	HRTIMER_BASE_MONOTONIC,
	HRTIMER_BASE_REALTIME,
	HRTIMER_BASE_BOOTTIME,
	HRTIMER_BASE_TAI,
	HRTIMER_BASE_MONOTONIC_SOFT,
	HRTIMER_BASE_REALTIME_SOFT,
	HRTIMER_BASE_BOOTTIME_SOFT,
	HRTIMER_BASE_TAI_SOFT,
	HRTIMER_MAX_CLOCK_BASES,
};

可以的:

/*
 * Mode arguments of xxx_hrtimer functions:
 *
 * HRTIMER_MODE_ABS		- Time value is absolute
 * HRTIMER_MODE_REL		- Time value is relative to now
 * HRTIMER_MODE_PINNED		- Timer is bound to CPU (is only considered
 *				  when starting the timer)
 * HRTIMER_MODE_SOFT		- Timer callback function will be executed in
 *				  soft irq context
 * HRTIMER_MODE_HARD		- Timer callback function will be executed in
 *				  hard irq context even on PREEMPT_RT.
 */
enum hrtimer_mode {
	HRTIMER_MODE_ABS	= 0x00,
	HRTIMER_MODE_REL	= 0x01,
	HRTIMER_MODE_PINNED	= 0x02,
	HRTIMER_MODE_SOFT	= 0x04,
	HRTIMER_MODE_HARD	= 0x08,
  // ...
}

从 uerspace 的 clock_id 到 system 的内容

static const struct k_clock *clockid_to_kclock(const clockid_t id)
{
	clockid_t idx = id;

	if (id < 0) {
		return (id & CLOCKFD_MASK) == CLOCKFD ?
			&clock_posix_dynamic : &clock_posix_cpu;
	}

	if (id >= ARRAY_SIZE(posix_clocks))
		return NULL;

	return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
}

static const struct k_clock * const posix_clocks[] = {
	[CLOCK_REALTIME]		= &clock_realtime,
	[CLOCK_MONOTONIC]		= &clock_monotonic,
	[CLOCK_PROCESS_CPUTIME_ID]	= &clock_process,
	[CLOCK_THREAD_CPUTIME_ID]	= &clock_thread,
	[CLOCK_MONOTONIC_RAW]		= &clock_monotonic_raw,
	[CLOCK_REALTIME_COARSE]		= &clock_realtime_coarse,
	[CLOCK_MONOTONIC_COARSE]	= &clock_monotonic_coarse,
	[CLOCK_BOOTTIME]		= &clock_boottime,
	[CLOCK_REALTIME_ALARM]		= &alarm_clock,
	[CLOCK_BOOTTIME_ALARM]		= &alarm_clock,
	[CLOCK_TAI]			= &clock_tai,
};

clock_posix_dynamic 和 clock_posix_cpu

只能理解第一个，无法理解第二个了。

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