Function vatpit_handler

freebsd/amd64/vmm/io/vatpit.c:338–419

}

int
vatpit_handler(struct vm *vm, int vcpuid, bool in, int port, int bytes,
    uint32_t *eax)
{
	struct vatpit *vatpit;
	struct channel *c;
	uint8_t val;
	int error;

	vatpit = vm_atpit(vm);

	if (bytes != 1)
		return (-1);

	val = *eax;

	if (port == TIMER_MODE) {
		if (in) {
			VM_CTR0(vatpit->vm, "vatpit attempt to read mode");
			return (-1);
		}

		VATPIT_LOCK(vatpit);
		error = vatpit_update_mode(vatpit, val);
		VATPIT_UNLOCK(vatpit);

		return (error);
	}

	/* counter ports */
	KASSERT(port >= TIMER_CNTR0 && port <= TIMER_CNTR2,
	    ("invalid port 0x%x", port));
	c = &vatpit->channel[port - TIMER_CNTR0];

	VATPIT_LOCK(vatpit);
	if (in && c->slatched) {
		/*
		 * Return the status byte if latched
		 */
		*eax = c->status;
		c->slatched = false;
		c->status = 0;
	} else if (in) {
		/*
		 * The spec says that once the output latch is completely
		 * read it should revert to "following" the counter. Use
		 * the free running counter for this case (i.e. Linux
		 * TSC calibration). Assuming the access mode is 16-bit,
		 * toggle the MSB/LSB bit on each read.
		 */
		if (c->olbyte == 0) {
			uint16_t tmp;

			tmp = pit_update_counter(vatpit, c, false);
			if (c->frbyte)
				tmp >>= 8;
			tmp &= 0xff;
			*eax = tmp;