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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: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Marcelo Tosatti 2009-04-08 13:14:19 -03:00 committed by Avi Kivity
parent 2906e79f21
commit ede2ccc517
1 changed files with 15 additions and 11 deletions
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26
arch/x86/kvm/i8254.c
View File

@ -104,13 +104,18 @@ static s64 __kpit_elapsed(struct kvm *kvm)
ktime_t remaining; ktime_t remaining;
struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state; 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); remaining = hrtimer_expires_remaining(&ps->pit_timer.timer);
if (ktime_to_ns(remaining) < 0) elapsed = ps->pit_timer.period - ktime_to_ns(remaining);
remaining = ktime_set(0, 0); elapsed = mod_64(elapsed, ps->pit_timer.period);
elapsed = ps->pit_timer.period;
if (ktime_to_ns(remaining) <= ps->pit_timer.period)
elapsed = ps->pit_timer.period - ktime_to_ns(remaining);
return elapsed; 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 */ /* TODO The new value only affected after the retriggered */
hrtimer_cancel(&pt->timer); hrtimer_cancel(&pt->timer);
pt->period = (is_period == 0) ? 0 : interval; pt->period = interval;
ps->is_periodic = is_period; ps->is_periodic = is_period;
pt->timer.function = kvm_timer_fn; 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); 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, * The largest possible initial count is 0; this is equivalent
* seems some tricky OS like Windows XP depends on IRQ0 interrupt * to 216 for binary counting and 104 for BCD counting.
* when booting up.
* So here setting initialize rate for it, and not a specific number
*/ */
if (val == 0) if (val == 0)
val = 0x10000; val = 0x10000;
@ -322,6 +325,7 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
/* Two types of timer /* Two types of timer
* mode 1 is one shot, mode 2 is period, otherwise del timer */ * mode 1 is one shot, mode 2 is period, otherwise del timer */
switch (ps->channels[0].mode) { switch (ps->channels[0].mode) {
case 0:
case 1: case 1:
/* FIXME: enhance mode 4 precision */ /* FIXME: enhance mode 4 precision */
case 4: case 4: