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Commit ede2ccc5 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Avi Kivity
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KVM: PIT: fix count read and mode 0 handling 



Commit 46ee278652f4cbd51013471b64c7897ba9bcd1b1 causes Solaris 10
to hang on boot.

Assuming that PIT counter reads should return 0 for an expired timer
is wrong: when it is active, the counter never stops (see comment on
__kpit_elapsed).

Also arm a one shot timer for mode 0.

Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 2906e79f

arch/x86/kvm/i8254.c

+15 −11
Original line number Diff line number Diff line
@@ -104,13 +104,18 @@ static s64 __kpit_elapsed(struct kvm *kvm) 
	ktime_t remaining;

	struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;



	/*

	 * The Counter does not stop when it reaches zero. In

	 * Modes 0, 1, 4, and 5 the Counter ``wraps around'' to

	 * the highest count, either FFFF hex for binary counting

	 * or 9999 for BCD counting, and continues counting.

	 * Modes 2 and 3 are periodic; the Counter reloads

	 * itself with the initial count and continues counting

	 * from there.

	 */

	remaining = hrtimer_expires_remaining(&ps->pit_timer.timer);

	if (ktime_to_ns(remaining) < 0)

		remaining = ktime_set(0, 0);



	elapsed = ps->pit_timer.period;

	if (ktime_to_ns(remaining) <= ps->pit_timer.period)

	elapsed = ps->pit_timer.period - ktime_to_ns(remaining);

	elapsed = mod_64(elapsed, ps->pit_timer.period);



	return elapsed;

}
@@ -280,7 +285,7 @@ static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period) 


	/* TODO The new value only affected after the retriggered */

	hrtimer_cancel(&pt->timer);

	pt->period = (is_period == 0) ? 0 : interval;

	pt->period = interval;

	ps->is_periodic = is_period;



	pt->timer.function = kvm_timer_fn;
@@ -304,10 +309,8 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val) 
	pr_debug("pit: load_count val is %d, channel is %d\n", val, channel);



	/*

	 * Though spec said the state of 8254 is undefined after power-up,

	 * seems some tricky OS like Windows XP depends on IRQ0 interrupt

	 * when booting up.

	 * So here setting initialize rate for it, and not a specific number

	 * The largest possible initial count is 0; this is equivalent

	 * to 216 for binary counting and 104 for BCD counting.

	 */

	if (val == 0)

		val = 0x10000;
@@ -322,6 +325,7 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val) 
	/* Two types of timer

	 * mode 1 is one shot, mode 2 is period, otherwise del timer */

	switch (ps->channels[0].mode) {

	case 0:

	case 1:

        /* FIXME: enhance mode 4 precision */

	case 4: