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[Qemu-devel] [PATCH v12 1/9] hw/ptimer: Fix issues caused by the adjuste
From: |
Dmitry Osipenko |
Subject: |
[Qemu-devel] [PATCH v12 1/9] hw/ptimer: Fix issues caused by the adjusted timer limit value |
Date: |
Sat, 30 Jan 2016 19:43:10 +0300 |
Multiple issues here related to the timer with a adjusted .limit value:
1) ptimer_get_count() returns incorrect counter value for the disabled
timer after loading the counter with a small value, because adjusted limit
value is used instead of the original.
For instance:
1) ptimer_stop(t)
2) ptimer_set_period(t, 1)
3) ptimer_set_limit(t, 0, 1)
4) ptimer_get_count(t) <-- would return 10000 instead of 0
2) ptimer_get_count() might return incorrect value for the timer running
with a adjusted limit value.
For instance:
1) ptimer_stop(t)
2) ptimer_set_period(t, 1)
3) ptimer_set_limit(t, 10, 1)
4) ptimer_run(t)
5) ptimer_get_count(t) <-- might return value > 10
3) Neither ptimer_set_period() nor ptimer_set_freq() are adjusting the
limit value, so it is still possible to make timer timeout value
arbitrary small.
For instance:
1) ptimer_set_period(t, 10000)
2) ptimer_set_limit(t, 1, 0)
3) ptimer_set_period(t, 1) <-- bypass limit correction
Fix all of the above issues by adjusting timer period instead of the limit.
Perform the adjustment for periodic timer only. Use the delta value instead
of the limit to make decision whether adjustment is required, as limit could
be altered while timer is running, resulting in incorrect value returned by
ptimer_get_count.
Signed-off-by: Dmitry Osipenko <address@hidden>
Reviewed-by: Peter Crosthwaite <address@hidden>
---
hw/core/ptimer.c | 51 +++++++++++++++++++++++++++++++--------------------
1 file changed, 31 insertions(+), 20 deletions(-)
diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index edf077c..5edcd71 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -34,6 +34,9 @@ static void ptimer_trigger(ptimer_state *s)
static void ptimer_reload(ptimer_state *s)
{
+ uint32_t period_frac = s->period_frac;
+ uint64_t period = s->period;
+
if (s->delta == 0) {
ptimer_trigger(s);
s->delta = s->limit;
@@ -44,10 +47,24 @@ static void ptimer_reload(ptimer_state *s)
return;
}
+ /*
+ * Artificially limit timeout rate to something
+ * achievable under QEMU. Otherwise, QEMU spends all
+ * its time generating timer interrupts, and there
+ * is no forward progress.
+ * About ten microseconds is the fastest that really works
+ * on the current generation of host machines.
+ */
+
+ if (s->enabled == 1 && (s->delta * period < 10000) && !use_icount) {
+ period = 10000 / s->delta;
+ period_frac = 0;
+ }
+
s->last_event = s->next_event;
- s->next_event = s->last_event + s->delta * s->period;
- if (s->period_frac) {
- s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
+ s->next_event = s->last_event + s->delta * period;
+ if (period_frac) {
+ s->next_event += ((int64_t)period_frac * s->delta) >> 32;
}
timer_mod(s->timer, s->next_event);
}
@@ -82,6 +99,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
uint64_t div;
int clz1, clz2;
int shift;
+ uint32_t period_frac = s->period_frac;
+ uint64_t period = s->period;
+
+ if ((s->enabled == 1) && !use_icount && (s->delta * period <
10000)) {
+ period = 10000 / s->delta;
+ period_frac = 0;
+ }
/* We need to divide time by period, where time is stored in
rem (64-bit integer) and period is stored in period/period_frac
@@ -94,7 +118,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
*/
rem = s->next_event - now;
- div = s->period;
+ div = period;
clz1 = clz64(rem);
clz2 = clz64(div);
@@ -103,13 +127,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
rem <<= shift;
div <<= shift;
if (shift >= 32) {
- div |= ((uint64_t)s->period_frac << (shift - 32));
+ div |= ((uint64_t)period_frac << (shift - 32));
} else {
if (shift != 0)
- div |= (s->period_frac >> (32 - shift));
+ div |= (period_frac >> (32 - shift));
/* Look at remaining bits of period_frac and round div up if
necessary. */
- if ((uint32_t)(s->period_frac << shift))
+ if ((uint32_t)(period_frac << shift))
div += 1;
}
counter = rem / div;
@@ -181,19 +205,6 @@ void ptimer_set_freq(ptimer_state *s, uint32_t freq)
count = limit. */
void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
{
- /*
- * Artificially limit timeout rate to something
- * achievable under QEMU. Otherwise, QEMU spends all
- * its time generating timer interrupts, and there
- * is no forward progress.
- * About ten microseconds is the fastest that really works
- * on the current generation of host machines.
- */
-
- if (!use_icount && limit * s->period < 10000 && s->period) {
- limit = 10000 / s->period;
- }
-
s->limit = limit;
if (reload)
s->delta = limit;
--
2.7.0
- [Qemu-devel] [PATCH v12 0/9] PTimer fixes/features and ARM MPTimer conversion, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 1/9] hw/ptimer: Fix issues caused by the adjusted timer limit value,
Dmitry Osipenko <=
- [Qemu-devel] [PATCH v12 4/9] hw/ptimer: Support "on the fly" timer mode switch, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 3/9] hw/ptimer: Update .delta on period/freq change, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 8/9] hw/ptimer: Perform delayed tick instead of immediate if delta = 0, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 5/9] hw/ptimer: Introduce ptimer_get_limit, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 2/9] hw/ptimer: Perform counter wrap around if timer already expired, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 6/9] hw/ptimer: Legalize running with delta = load = 0 and abort on period = 0, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 7/9] hw/ptimer: Fix counter - 1 returned by ptimer_get_count for the active timer, Dmitry Osipenko, 2016/01/30
- [Qemu-devel] [PATCH v12 9/9] arm_mptimer: Convert to use ptimer, Dmitry Osipenko, 2016/01/30