summaryrefslogtreecommitdiff
path: root/arch/x86/kvm/i8254.c
diff options
context:
space:
mode:
authorMarcelo Tosatti <mtosatti@redhat.com>2009-04-08 20:14:19 +0400
committerAvi Kivity <avi@redhat.com>2009-06-10 12:48:39 +0400
commitede2ccc51742059d356d419260460cbbf3e36273 (patch)
tree9a38010c1d6c2fcdb3d566b2d154d5f8f6a14680 /arch/x86/kvm/i8254.c
parent2906e79f21a559e49611e1e188c4993cd45d9ce1 (diff)
downloadlinux-ede2ccc51742059d356d419260460cbbf3e36273.tar.xz
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>
Diffstat (limited to 'arch/x86/kvm/i8254.c')
-rw-r--r--arch/x86/kvm/i8254.c26
1 files changed, 15 insertions, 11 deletions
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index cf09bb64f141..4d6f0d293ee2 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -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 = 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: