[Qemu-devel] [PATCH v8 0/4] PTimer fixes and ARM MPTimer conversion

[Qemu-devel] [PATCH v8 0/4] PTimer fixes and ARM MPTimer conversion

[Dmitry Osipenko]

Changelog for ARM MPTimer QEMUTimer to ptimer conversion:

    V2: Fixed changing periodic timer counter value "on the fly". I added a
        test to the gist to cover that issue.

    V3: Fixed starting the timer with load = 0 and counter != 0, added tests
        to the gist for this issue. Changed vmstate version for all VMSD's,
        since loadvm doesn't check version of nested VMSD.

    V4: Fixed spurious IT bit set for the timer starting in the periodic mode
        with counter = 0. Test added.

    V5: Code cleanup, now depends on ptimer_set_limit() fix.

    V6: No code change, added test to check ptimer_get_count() with corrected
        .limit value.

    V7: No change.

    V8: No change.

ARM MPTimer tests: https://gist.github.com/digetx/dbd46109503b1a91941a


Patch for ptimer is introduced since V5 of "ARM MPTimer conversion".

Changelog for the "ptimer fixes" patch:

    V5: Only fixed ptimer_set_limit() for the disabled timer.

    V6: As was pointed by Peter Maydell, there are other issues beyond
        ptimer_set_limit(), so V6 supposed to cover all those issues.

    V7: Added accidentally removed !use_icount check.
        Added missed "else" statement.

    V8: Adjust period instead of the limit and do it for periodic timer only
        (.limit adjusting bug). Added patch/fix for freq/period change and
        ptimer_get_count() improvement.

Dmitry Osipenko (4):
  hw/ptimer: Fix issues caused by the adjusted timer limit value
  hw/ptimer: Perform tick and counter wrap around if timer already
    expired
  hw/ptimer: Update .delta on period/freq change
  arm_mptimer: Convert to use ptimer

 hw/core/ptimer.c               |  94 ++++++++++++++++++++++++-----------
 hw/timer/arm_mptimer.c         | 110 ++++++++++++++++++-----------------------
 include/hw/timer/arm_mptimer.h |   4 +-
 3 files changed, 115 insertions(+), 93 deletions(-)

-- 
2.6.4

[Qemu-devel] [PATCH v8 1/4] hw/ptimer: Fix issues caused by the adjusted timer limit value

[Dmitry Osipenko]

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.
Do the adjust for periodic timer only.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/core/ptimer.c | 59 ++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 36 insertions(+), 23 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index edf077c..035af97 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -34,20 +34,39 @@ static void ptimer_trigger(ptimer_state *s)
 
 static void ptimer_reload(ptimer_state *s)
 {
-    if (s->delta == 0) {
+    uint32_t period_frac = s->period_frac;
+    uint64_t period = s->period;
+    uint64_t delta = s->delta;
+    uint64_t limit = s->limit;
+
+    if (delta == 0) {
         ptimer_trigger(s);
-        s->delta = s->limit;
+        delta = limit;
     }
-    if (s->delta == 0 || s->period == 0) {
+    if (delta == 0 || period == 0) {
         fprintf(stderr, "Timer with period zero, disabling\n");
         s->enabled = 0;
         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) && (limit * period < 10000)) {
+        period = 10000 / limit;
+        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 + delta * period;
+    if (period_frac) {
+        s->next_event += ((int64_t)period_frac * delta) >> 32;
     }
     timer_mod(s->timer, s->next_event);
 }
@@ -82,6 +101,8 @@ 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;
 
             /* We need to divide time by period, where time is stored in
                rem (64-bit integer) and period is stored in period/period_frac
@@ -93,8 +114,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
                backwards.
             */
 
+            if ((s->enabled == 1) && (s->limit * period < 10000)) {
+                period = 10000 / s->limit;
+                period_frac = 0;
+            }
+
             rem = s->next_event - now;
-            div = s->period;
+            div = period;
 
             clz1 = clz64(rem);
             clz2 = clz64(div);
@@ -103,13 +129,13 @@ 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 +207,6 @@ 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;
-- 
2.6.4

[Qemu-devel] [PATCH v8 2/4] hw/ptimer: Perform tick and counter wrap around if timer already expired

[Dmitry Osipenko]

ptimer_get_count() might be called while QEMU timer already been expired.
In that case ptimer would return counter = 0, which might be undesirable
in case of polled timer. Do counter wrap around for periodic timer to keep
it distributed.

In addition, there is no reason to keep expired timer tick deferred, so
just perform the tick from ptimer_get_count().

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/core/ptimer.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index 035af97..96a6c7a 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -85,15 +85,21 @@ static void ptimer_tick(void *opaque)
 
 uint64_t ptimer_get_count(ptimer_state *s)
 {
+    int enabled = s->enabled;
     int64_t now;
+    int64_t next;
     uint64_t counter;
+    int expired;
+    int oneshot;
 
-    if (s->enabled) {
+    if (enabled) {
         now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        next = s->next_event;
+        expired = (now - next >= 0);
+        oneshot = (enabled == 2);
         /* Figure out the current counter value.  */
-        if (now - s->next_event > 0
-            || s->period == 0) {
-            /* Prevent timer underflowing if it should already have
+        if (s->period == 0 || (expired && oneshot)) {
+            /* Prevent one-shot timer underflowing if it should already have
                triggered.  */
             counter = 0;
         } else {
@@ -114,12 +120,12 @@ uint64_t ptimer_get_count(ptimer_state *s)
                backwards.
             */
 
-            if ((s->enabled == 1) && (s->limit * period < 10000)) {
+            if (!oneshot && (s->limit * period < 10000)) {
                 period = 10000 / s->limit;
                 period_frac = 0;
             }
 
-            rem = s->next_event - now;
+            rem = expired ? now - next : next - now;
             div = period;
 
             clz1 = clz64(rem);
@@ -139,6 +145,23 @@ uint64_t ptimer_get_count(ptimer_state *s)
                     div += 1;
             }
             counter = rem / div;
+
+            if (expired) {
+                /* Wrap around periodic counter.  */
+                counter = s->delta = s->limit - counter % s->limit;
+            }
+        }
+
+        if (expired) {
+            if (oneshot) {
+                ptimer_tick(s);
+            } else {
+                /* Don't use ptimer_tick() for the periodic timer since it
+                 * would reset the delta value.
+                 */
+                ptimer_trigger(s);
+                ptimer_reload(s);
+            }
         }
     } else {
         counter = s->delta;
-- 
2.6.4

[Qemu-devel] [PATCH v8 3/4] hw/ptimer: Update .delta on period/freq change

[Dmitry Osipenko]

Delta value must be updated on period/freq change, otherwise running timer
would be restarted (counter reloaded with old delta). Only m68k/mcf520x
and arm/arm_timer devices are currently doing freq change correctly, i.e.
stopping the timer. Perform delta update to fix affected devices and
eliminate potential further mistakes.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/core/ptimer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index 96a6c7a..8c2dd9f 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -207,6 +207,7 @@ void ptimer_stop(ptimer_state *s)
 /* Set counter increment interval in nanoseconds.  */
 void ptimer_set_period(ptimer_state *s, int64_t period)
 {
+    s->delta = ptimer_get_count(s);
     s->period = period;
     s->period_frac = 0;
     if (s->enabled) {
@@ -218,6 +219,7 @@ void ptimer_set_period(ptimer_state *s, int64_t period)
 /* Set counter frequency in Hz.  */
 void ptimer_set_freq(ptimer_state *s, uint32_t freq)
 {
+    s->delta = ptimer_get_count(s);
     s->period = 1000000000ll / freq;
     s->period_frac = (1000000000ll << 32) / freq;
     if (s->enabled) {
-- 
2.6.4

[Qemu-devel] [PATCH v8 4/4] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

Current ARM MPTimer implementation uses QEMUTimer for the actual timer,
this implementation isn't complete and mostly tries to duplicate of what
generic ptimer is already doing fine.

Conversion to ptimer brings the following benefits and fixes:
	- Simple timer pausing implementation
	- Fixes counter value preservation after stopping the timer
	- Code simplification and reduction

Bump VMSD to version 3, since VMState is changed and is not compatible
with the previous implementation.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/timer/arm_mptimer.c         | 110 ++++++++++++++++++-----------------------
 include/hw/timer/arm_mptimer.h |   4 +-
 2 files changed, 49 insertions(+), 65 deletions(-)

diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
index 3e59c2a..c06da5e 100644
--- a/hw/timer/arm_mptimer.c
+++ b/hw/timer/arm_mptimer.c
@@ -19,8 +19,9 @@
  * with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "hw/ptimer.h"
 #include "hw/timer/arm_mptimer.h"
-#include "qemu/timer.h"
+#include "qemu/main-loop.h"
 #include "qom/cpu.h"
 
 /* This device implements the per-cpu private timer and watchdog block
@@ -47,28 +48,10 @@ static inline uint32_t timerblock_scale(TimerBlock *tb)
     return (((tb->control >> 8) & 0xff) + 1) * 10;
 }
 
-static void timerblock_reload(TimerBlock *tb, int restart)
-{
-    if (tb->count == 0) {
-        return;
-    }
-    if (restart) {
-        tb->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-    }
-    tb->tick += (int64_t)tb->count * timerblock_scale(tb);
-    timer_mod(tb->timer, tb->tick);
-}
-
 static void timerblock_tick(void *opaque)
 {
     TimerBlock *tb = (TimerBlock *)opaque;
     tb->status = 1;
-    if (tb->control & 2) {
-        tb->count = tb->load;
-        timerblock_reload(tb, 0);
-    } else {
-        tb->count = 0;
-    }
     timerblock_update_irq(tb);
 }
 
@@ -76,21 +59,11 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
                                 unsigned size)
 {
     TimerBlock *tb = (TimerBlock *)opaque;
-    int64_t val;
     switch (addr) {
     case 0: /* Load */
         return tb->load;
     case 4: /* Counter.  */
-        if (((tb->control & 1) == 0) || (tb->count == 0)) {
-            return 0;
-        }
-        /* Slow and ugly, but hopefully won't happen too often.  */
-        val = tb->tick - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-        val /= timerblock_scale(tb);
-        if (val < 0) {
-            val = 0;
-        }
-        return val;
+        return ptimer_get_count(tb->timer);
     case 8: /* Control.  */
         return tb->control;
     case 12: /* Interrupt status.  */
@@ -100,6 +73,19 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
     }
 }
 
+static void timerblock_run(TimerBlock *tb, uint64_t count, int set_count)
+{
+    if (set_count) {
+        if (((tb->control & 3) == 3) && (count == 0)) {
+            count = tb->load;
+        }
+        ptimer_set_count(tb->timer, count);
+    }
+    if ((tb->control & 1) && (count != 0)) {
+        ptimer_run(tb->timer, !(tb->control & 2));
+    }
+}
+
 static void timerblock_write(void *opaque, hwaddr addr,
                              uint64_t value, unsigned size)
 {
@@ -108,32 +94,34 @@ static void timerblock_write(void *opaque, hwaddr addr,
     switch (addr) {
     case 0: /* Load */
         tb->load = value;
-        /* Fall through.  */
-    case 4: /* Counter.  */
-        if ((tb->control & 1) && tb->count) {
-            /* Cancel the previous timer.  */
-            timer_del(tb->timer);
+        /* Setting load to 0 stops the timer.  */
+        if (tb->load == 0) {
+            ptimer_stop(tb->timer);
         }
-        tb->count = value;
-        if (tb->control & 1) {
-            timerblock_reload(tb, 1);
+        ptimer_set_limit(tb->timer, tb->load, 1);
+        timerblock_run(tb, tb->load, 0);
+        break;
+    case 4: /* Counter.  */
+        /* Setting counter to 0 stops the one-shot timer.  */
+        if (!(tb->control & 2) && (value == 0)) {
+            ptimer_stop(tb->timer);
         }
+        timerblock_run(tb, value, 1);
         break;
     case 8: /* Control.  */
         old = tb->control;
         tb->control = value;
-        if (value & 1) {
-            if ((old & 1) && (tb->count != 0)) {
-                /* Do nothing if timer is ticking right now.  */
-                break;
-            }
-            if (tb->control & 2) {
-                tb->count = tb->load;
-            }
-            timerblock_reload(tb, 1);
-        } else if (old & 1) {
-            /* Shutdown the timer.  */
-            timer_del(tb->timer);
+        /* Timer mode switch requires ptimer to be stopped.  */
+        if ((old & 3) != (tb->control & 3)) {
+            ptimer_stop(tb->timer);
+        }
+        if (!(tb->control & 1)) {
+            break;
+        }
+        ptimer_set_period(tb->timer, timerblock_scale(tb));
+        if ((old & 3) != (tb->control & 3)) {
+            value = ptimer_get_count(tb->timer);
+            timerblock_run(tb, value, 1);
         }
         break;
     case 12: /* Interrupt status.  */
@@ -184,13 +172,12 @@ static const MemoryRegionOps timerblock_ops = {
 
 static void timerblock_reset(TimerBlock *tb)
 {
-    tb->count = 0;
     tb->load = 0;
     tb->control = 0;
     tb->status = 0;
-    tb->tick = 0;
     if (tb->timer) {
-        timer_del(tb->timer);
+        ptimer_stop(tb->timer);
+        ptimer_set_limit(tb->timer, 0, 1);
     }
 }
 
@@ -235,7 +222,8 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
      */
     for (i = 0; i < s->num_cpu; i++) {
         TimerBlock *tb = &s->timerblock[i];
-        tb->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, timerblock_tick, tb);
+        QEMUBH *bh = qemu_bh_new(timerblock_tick, tb);
+        tb->timer = ptimer_init(bh);
         sysbus_init_irq(sbd, &tb->irq);
         memory_region_init_io(&tb->iomem, OBJECT(s), &timerblock_ops, tb,
                               "arm_mptimer_timerblock", 0x20);
@@ -245,26 +233,24 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
 
 static const VMStateDescription vmstate_timerblock = {
     .name = "arm_mptimer_timerblock",
-    .version_id = 2,
-    .minimum_version_id = 2,
+    .version_id = 3,
+    .minimum_version_id = 3,
     .fields = (VMStateField[]) {
-        VMSTATE_UINT32(count, TimerBlock),
         VMSTATE_UINT32(load, TimerBlock),
         VMSTATE_UINT32(control, TimerBlock),
         VMSTATE_UINT32(status, TimerBlock),
-        VMSTATE_INT64(tick, TimerBlock),
-        VMSTATE_TIMER_PTR(timer, TimerBlock),
+        VMSTATE_PTIMER(timer, TimerBlock),
         VMSTATE_END_OF_LIST()
     }
 };
 
 static const VMStateDescription vmstate_arm_mptimer = {
     .name = "arm_mptimer",
-    .version_id = 2,
-    .minimum_version_id = 2,
+    .version_id = 3,
+    .minimum_version_id = 3,
     .fields = (VMStateField[]) {
         VMSTATE_STRUCT_VARRAY_UINT32(timerblock, ARMMPTimerState, num_cpu,
-                                     2, vmstate_timerblock, TimerBlock),
+                                     3, vmstate_timerblock, TimerBlock),
         VMSTATE_END_OF_LIST()
     }
 };
diff --git a/include/hw/timer/arm_mptimer.h b/include/hw/timer/arm_mptimer.h
index b34cba0..93db61b 100644
--- a/include/hw/timer/arm_mptimer.h
+++ b/include/hw/timer/arm_mptimer.h
@@ -27,12 +27,10 @@
 
 /* State of a single timer or watchdog block */
 typedef struct {
-    uint32_t count;
     uint32_t load;
     uint32_t control;
     uint32_t status;
-    int64_t tick;
-    QEMUTimer *timer;
+    struct ptimer_state *timer;
     qemu_irq irq;
     MemoryRegion iomem;
 } TimerBlock;
-- 
2.6.4

Re: [Qemu-devel] [PATCH v8 1/4] hw/ptimer: Fix issues caused by the adjusted timer limit value

[Peter Crosthwaite]

On Tue, Jan 05, 2016 at 05:33:26AM +0300, Dmitry Osipenko wrote:
> 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.
> Do the adjust for periodic timer only.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  hw/core/ptimer.c | 59 ++++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 36 insertions(+), 23 deletions(-)
> 
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index edf077c..035af97 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -34,20 +34,39 @@ static void ptimer_trigger(ptimer_state *s)
>  
>  static void ptimer_reload(ptimer_state *s)
>  {
> -    if (s->delta == 0) {
> +    uint32_t period_frac = s->period_frac;
> +    uint64_t period = s->period;
> +    uint64_t delta = s->delta;
> +    uint64_t limit = s->limit;
> +

Localising these variables is out of scope of the change. I think you can
just use s->foo and if you want to cleanup, it should be a separate
patch.

> +    if (delta == 0) {
>          ptimer_trigger(s);
> -        s->delta = s->limit;
> +        delta = limit;
>      }
> -    if (s->delta == 0 || s->period == 0) {
> +    if (delta == 0 || period == 0) {
>          fprintf(stderr, "Timer with period zero, disabling\n");
>          s->enabled = 0;
>          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) && (limit * period < 10000)) {
> +        period = 10000 / limit;
> +        period_frac = 0;
> +    }
> +

I think it should be ok to just update s->period and s->period_frac ...

>      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 + delta * period;
> +    if (period_frac) {
> +        s->next_event += ((int64_t)period_frac * delta) >> 32;
>      }
>      timer_mod(s->timer, s->next_event);
>  }
> @@ -82,6 +101,8 @@ 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;
>  
>              /* We need to divide time by period, where time is stored in
>                 rem (64-bit integer) and period is stored in period/period_frac
> @@ -93,8 +114,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
>                 backwards.
>              */
>  
> +            if ((s->enabled == 1) && (s->limit * period < 10000)) {
> +                period = 10000 / s->limit;
> +                period_frac = 0;
> +            }
> +

... and then this (and the local variables) become obsolete. Can get_count()
blindly use the period and period_frac as used by ptimer_reload?

>              rem = s->next_event - now;
> -            div = s->period;
> +            div = period;
>  
>              clz1 = clz64(rem);
>              clz2 = clz64(div);
> @@ -103,13 +129,13 @@ 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 +207,6 @@ 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) {

This original rate limiting code is gated on icount, so I think then
new way should be the same.

Regards,
Peter

> -        limit = 10000 / s->period;
> -    }
> -
>      s->limit = limit;
>      if (reload)
>          s->delta = limit;
> -- 
> 2.6.4
> 

Re: [Qemu-devel] [PATCH v8 2/4] hw/ptimer: Perform tick and counter wrap around if timer already expired

[Peter Crosthwaite]

On Tue, Jan 05, 2016 at 05:33:27AM +0300, Dmitry Osipenko wrote:
> ptimer_get_count() might be called while QEMU timer already been expired.
> In that case ptimer would return counter = 0, which might be undesirable
> in case of polled timer. Do counter wrap around for periodic timer to keep
> it distributed.
> 
> In addition, there is no reason to keep expired timer tick deferred, so
> just perform the tick from ptimer_get_count().
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  hw/core/ptimer.c | 35 +++++++++++++++++++++++++++++------
>  1 file changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index 035af97..96a6c7a 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -85,15 +85,21 @@ static void ptimer_tick(void *opaque)
>  
>  uint64_t ptimer_get_count(ptimer_state *s)
>  {
> +    int enabled = s->enabled;

Variable localisation not needed.

>      int64_t now;
> +    int64_t next;
>      uint64_t counter;
> +    int expired;
> +    int oneshot;

Variable defs can be localised to the if (enabled) (even though now
in original code doesn't do that).

>  
> -    if (s->enabled) {
> +    if (enabled) {
>          now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +        next = s->next_event;
> +        expired = (now - next >= 0);
> +        oneshot = (enabled == 2);
>          /* Figure out the current counter value.  */

This comment is now out of place.

> -        if (now - s->next_event > 0
> -            || s->period == 0) {
> -            /* Prevent timer underflowing if it should already have
> +        if (s->period == 0 || (expired && oneshot)) {
> +            /* Prevent one-shot timer underflowing if it should already have
>                 triggered.  */
>              counter = 0;
>          } else {
> @@ -114,12 +120,12 @@ uint64_t ptimer_get_count(ptimer_state *s)
>                 backwards.
>              */
>  
> -            if ((s->enabled == 1) && (s->limit * period < 10000)) {
> +            if (!oneshot && (s->limit * period < 10000)) {
>                  period = 10000 / s->limit;
>                  period_frac = 0;
>              }
>  
> -            rem = s->next_event - now;
> +            rem = expired ? now - next : next - now;
>              div = period;
>  
>              clz1 = clz64(rem);
> @@ -139,6 +145,23 @@ uint64_t ptimer_get_count(ptimer_state *s)
>                      div += 1;
>              }
>              counter = rem / div;
> +
> +            if (expired) {
> +                /* Wrap around periodic counter.  */
> +                counter = s->delta = s->limit - counter % s->limit;

Why do you update the delta here?

Also can you just get ptimer_reload to do the modulo math for you? If the
timer is !oneshot and expired, then you call ptimer_reload anyway,
which will update next_event. When the expired test returns false
you can just reliably use the original logic involving now and next.

> +            }
> +        }
> +
> +        if (expired) {
> +            if (oneshot) {

This if-else has a lot of common structure with the one above. I think
they could be merged.

Regards,
Peter

> +                ptimer_tick(s);
> +            } else {
> +                /* Don't use ptimer_tick() for the periodic timer since it
> +                 * would reset the delta value.
> +                 */
> +                ptimer_trigger(s);
> +                ptimer_reload(s);
> +            }
>          }
>      } else {
>          counter = s->delta;
> -- 
> 2.6.4
> 

Re: [Qemu-devel] [PATCH v8 3/4] hw/ptimer: Update .delta on period/freq change

[Peter Crosthwaite]

On Tue, Jan 05, 2016 at 05:33:28AM +0300, Dmitry Osipenko wrote:
> Delta value must be updated on period/freq change, otherwise running timer
> would be restarted (counter reloaded with old delta). Only m68k/mcf520x
> and arm/arm_timer devices are currently doing freq change correctly, i.e.
> stopping the timer. Perform delta update to fix affected devices and
> eliminate potential further mistakes.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>

Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>

> ---
>  hw/core/ptimer.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index 96a6c7a..8c2dd9f 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -207,6 +207,7 @@ void ptimer_stop(ptimer_state *s)
>  /* Set counter increment interval in nanoseconds.  */
>  void ptimer_set_period(ptimer_state *s, int64_t period)
>  {
> +    s->delta = ptimer_get_count(s);
>      s->period = period;
>      s->period_frac = 0;
>      if (s->enabled) {
> @@ -218,6 +219,7 @@ void ptimer_set_period(ptimer_state *s, int64_t period)
>  /* Set counter frequency in Hz.  */
>  void ptimer_set_freq(ptimer_state *s, uint32_t freq)
>  {
> +    s->delta = ptimer_get_count(s);
>      s->period = 1000000000ll / freq;
>      s->period_frac = (1000000000ll << 32) / freq;
>      if (s->enabled) {
> -- 
> 2.6.4
> 

Re: [Qemu-devel] [PATCH v8 2/4] hw/ptimer: Perform tick and counter wrap around if timer already expired

[Dmitry Osipenko]

06.01.2016 15:17, Peter Crosthwaite пишет:
> On Tue, Jan 05, 2016 at 05:33:27AM +0300, Dmitry Osipenko wrote:
>> ptimer_get_count() might be called while QEMU timer already been expired.
>> In that case ptimer would return counter = 0, which might be undesirable
>> in case of polled timer. Do counter wrap around for periodic timer to keep
>> it distributed.
>>
>> In addition, there is no reason to keep expired timer tick deferred, so
>> just perform the tick from ptimer_get_count().
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>   hw/core/ptimer.c | 35 +++++++++++++++++++++++++++++------
>>   1 file changed, 29 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
>> index 035af97..96a6c7a 100644
>> --- a/hw/core/ptimer.c
>> +++ b/hw/core/ptimer.c
>> @@ -85,15 +85,21 @@ static void ptimer_tick(void *opaque)
>>
>>   uint64_t ptimer_get_count(ptimer_state *s)
>>   {
>> +    int enabled = s->enabled;
>
> Variable localisation not needed.
>
>>       int64_t now;
>> +    int64_t next;
>>       uint64_t counter;
>> +    int expired;
>> +    int oneshot;
>
> Variable defs can be localised to the if (enabled) (even though now
> in original code doesn't do that).
>

Yeah, I just tried to keep original style here.

>>
>> -    if (s->enabled) {
>> +    if (enabled) {
>>           now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>> +        next = s->next_event;
>> +        expired = (now - next >= 0);
>> +        oneshot = (enabled == 2);
>>           /* Figure out the current counter value.  */
>
> This comment is now out of place.
>

Okay, will fix it.

>> -        if (now - s->next_event > 0
>> -            || s->period == 0) {
>> -            /* Prevent timer underflowing if it should already have
>> +        if (s->period == 0 || (expired && oneshot)) {
>> +            /* Prevent one-shot timer underflowing if it should already have
>>                  triggered.  */
>>               counter = 0;
>>           } else {
>> @@ -114,12 +120,12 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>                  backwards.
>>               */
>>
>> -            if ((s->enabled == 1) && (s->limit * period < 10000)) {
>> +            if (!oneshot && (s->limit * period < 10000)) {
>>                   period = 10000 / s->limit;
>>                   period_frac = 0;
>>               }
>>
>> -            rem = s->next_event - now;
>> +            rem = expired ? now - next : next - now;
>>               div = period;
>>
>>               clz1 = clz64(rem);
>> @@ -139,6 +145,23 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>                       div += 1;
>>               }
>>               counter = rem / div;
>> +
>> +            if (expired) {
>> +                /* Wrap around periodic counter.  */
>> +                counter = s->delta = s->limit - counter % s->limit;
>
> Why do you update the delta here?
>

Because we would want to schedule next tick based on current wrapped around 
counter value and not some arbitrary delta.

> Also can you just get ptimer_reload to do the modulo math for you? If the
> timer is !oneshot and expired, then you call ptimer_reload anyway,
> which will update next_event. When the expired test returns false
> you can just reliably use the original logic involving now and next.
>

Yes, that's what I changed in V9. Have you received it?

https://lists.nongnu.org/archive/html/qemu-devel/2016-01/msg00272.html

>> +            }
>> +        }
>> +
>> +        if (expired) {
>> +            if (oneshot) {
>
> This if-else has a lot of common structure with the one above. I think
> they could be merged.
>

That's a good suggestion, will do it in V10. Thanks.

> Regards,
> Peter
>
>> +                ptimer_tick(s);
>> +            } else {
>> +                /* Don't use ptimer_tick() for the periodic timer since it
>> +                 * would reset the delta value.
>> +                 */
>> +                ptimer_trigger(s);
>> +                ptimer_reload(s);
>> +            }
>>           }
>>       } else {
>>           counter = s->delta;
>> --
>> 2.6.4
>>


-- 
Dmitry

Re: [Qemu-devel] [PATCH v8 4/4] arm_mptimer: Convert to use ptimer

[Peter Crosthwaite]

On Tue, Jan 05, 2016 at 05:33:29AM +0300, Dmitry Osipenko wrote:
> Current ARM MPTimer implementation uses QEMUTimer for the actual timer,
> this implementation isn't complete and mostly tries to duplicate of what
> generic ptimer is already doing fine.
> 
> Conversion to ptimer brings the following benefits and fixes:
> 	- Simple timer pausing implementation
> 	- Fixes counter value preservation after stopping the timer
> 	- Code simplification and reduction
> 
> Bump VMSD to version 3, since VMState is changed and is not compatible
> with the previous implementation.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  hw/timer/arm_mptimer.c         | 110 ++++++++++++++++++-----------------------
>  include/hw/timer/arm_mptimer.h |   4 +-
>  2 files changed, 49 insertions(+), 65 deletions(-)
> 
> diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
> index 3e59c2a..c06da5e 100644
> --- a/hw/timer/arm_mptimer.c
> +++ b/hw/timer/arm_mptimer.c
> @@ -19,8 +19,9 @@
>   * with this program; if not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#include "hw/ptimer.h"
>  #include "hw/timer/arm_mptimer.h"
> -#include "qemu/timer.h"
> +#include "qemu/main-loop.h"
>  #include "qom/cpu.h"
>  
>  /* This device implements the per-cpu private timer and watchdog block
> @@ -47,28 +48,10 @@ static inline uint32_t timerblock_scale(TimerBlock *tb)
>      return (((tb->control >> 8) & 0xff) + 1) * 10;
>  }
>  
> -static void timerblock_reload(TimerBlock *tb, int restart)
> -{
> -    if (tb->count == 0) {
> -        return;
> -    }
> -    if (restart) {
> -        tb->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> -    }
> -    tb->tick += (int64_t)tb->count * timerblock_scale(tb);
> -    timer_mod(tb->timer, tb->tick);
> -}
> -
>  static void timerblock_tick(void *opaque)
>  {
>      TimerBlock *tb = (TimerBlock *)opaque;
>      tb->status = 1;
> -    if (tb->control & 2) {
> -        tb->count = tb->load;
> -        timerblock_reload(tb, 0);
> -    } else {
> -        tb->count = 0;
> -    }
>      timerblock_update_irq(tb);
>  }
>  
> @@ -76,21 +59,11 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
>                                  unsigned size)
>  {
>      TimerBlock *tb = (TimerBlock *)opaque;
> -    int64_t val;
>      switch (addr) {
>      case 0: /* Load */
>          return tb->load;
>      case 4: /* Counter.  */
> -        if (((tb->control & 1) == 0) || (tb->count == 0)) {
> -            return 0;
> -        }
> -        /* Slow and ugly, but hopefully won't happen too often.  */
> -        val = tb->tick - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> -        val /= timerblock_scale(tb);
> -        if (val < 0) {
> -            val = 0;
> -        }
> -        return val;
> +        return ptimer_get_count(tb->timer);
>      case 8: /* Control.  */
>          return tb->control;
>      case 12: /* Interrupt status.  */
> @@ -100,6 +73,19 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
>      }
>  }
>  
> +static void timerblock_run(TimerBlock *tb, uint64_t count, int set_count)
> +{
> +    if (set_count) {
> +        if (((tb->control & 3) == 3) && (count == 0)) {

Parentheses around == expressions should not be needed.

> +            count = tb->load;
> +        }
> +        ptimer_set_count(tb->timer, count);
> +    }
> +    if ((tb->control & 1) && (count != 0)) {

This can check against tb->load instead of count to avoid dummy
pass of tb->load to this fn ...

> +        ptimer_run(tb->timer, !(tb->control & 2));
> +    }
> +}
> +
>  static void timerblock_write(void *opaque, hwaddr addr,
>                               uint64_t value, unsigned size)
>  {
> @@ -108,32 +94,34 @@ static void timerblock_write(void *opaque, hwaddr addr,
>      switch (addr) {
>      case 0: /* Load */
>          tb->load = value;
> -        /* Fall through.  */
> -    case 4: /* Counter.  */
> -        if ((tb->control & 1) && tb->count) {
> -            /* Cancel the previous timer.  */
> -            timer_del(tb->timer);
> +        /* Setting load to 0 stops the timer.  */
> +        if (tb->load == 0) {
> +            ptimer_stop(tb->timer);
>          }
> -        tb->count = value;
> -        if (tb->control & 1) {
> -            timerblock_reload(tb, 1);
> +        ptimer_set_limit(tb->timer, tb->load, 1);
> +        timerblock_run(tb, tb->load, 0);
> +        break;
> +    case 4: /* Counter.  */
> +        /* Setting counter to 0 stops the one-shot timer.  */
> +        if (!(tb->control & 2) && (value == 0)) {
> +            ptimer_stop(tb->timer);
>          }
> +        timerblock_run(tb, value, 1);

... then this would just need to be elsed.

>          break;
>      case 8: /* Control.  */
>          old = tb->control;
>          tb->control = value;
> -        if (value & 1) {
> -            if ((old & 1) && (tb->count != 0)) {
> -                /* Do nothing if timer is ticking right now.  */
> -                break;
> -            }
> -            if (tb->control & 2) {
> -                tb->count = tb->load;
> -            }
> -            timerblock_reload(tb, 1);
> -        } else if (old & 1) {
> -            /* Shutdown the timer.  */
> -            timer_del(tb->timer);
> +        /* Timer mode switch requires ptimer to be stopped.  */

Is it worth adding this to ptimer? It seems ptimer can now handle
every other case of running configuration change except this one
case.

> +        if ((old & 3) != (tb->control & 3)) {
> +            ptimer_stop(tb->timer);
> +        }
> +        if (!(tb->control & 1)) {
> +            break;
> +        }
> +        ptimer_set_period(tb->timer, timerblock_scale(tb));
> +        if ((old & 3) != (tb->control & 3)) {
> +            value = ptimer_get_count(tb->timer);
> +            timerblock_run(tb, value, 1);

Is this reachable when the load value is still 0?

Following on from the suggested refactor before, I think timerblock_run
should split off the count set to a new helper. Then this is

timerblock_setcount(tb, value);
timerblock_run(tb);

and the boolean arg and dummy pass of tb->load as count are unneeded.

Regards,
Peter

>          }
>          break;
>      case 12: /* Interrupt status.  */
> @@ -184,13 +172,12 @@ static const MemoryRegionOps timerblock_ops = {
>  
>  static void timerblock_reset(TimerBlock *tb)
>  {
> -    tb->count = 0;
>      tb->load = 0;
>      tb->control = 0;
>      tb->status = 0;
> -    tb->tick = 0;
>      if (tb->timer) {
> -        timer_del(tb->timer);
> +        ptimer_stop(tb->timer);
> +        ptimer_set_limit(tb->timer, 0, 1);
>      }
>  }
>  
> @@ -235,7 +222,8 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
>       */
>      for (i = 0; i < s->num_cpu; i++) {
>          TimerBlock *tb = &s->timerblock[i];
> -        tb->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, timerblock_tick, tb);
> +        QEMUBH *bh = qemu_bh_new(timerblock_tick, tb);
> +        tb->timer = ptimer_init(bh);
>          sysbus_init_irq(sbd, &tb->irq);
>          memory_region_init_io(&tb->iomem, OBJECT(s), &timerblock_ops, tb,
>                                "arm_mptimer_timerblock", 0x20);
> @@ -245,26 +233,24 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
>  
>  static const VMStateDescription vmstate_timerblock = {
>      .name = "arm_mptimer_timerblock",
> -    .version_id = 2,
> -    .minimum_version_id = 2,
> +    .version_id = 3,
> +    .minimum_version_id = 3,
>      .fields = (VMStateField[]) {
> -        VMSTATE_UINT32(count, TimerBlock),
>          VMSTATE_UINT32(load, TimerBlock),
>          VMSTATE_UINT32(control, TimerBlock),
>          VMSTATE_UINT32(status, TimerBlock),
> -        VMSTATE_INT64(tick, TimerBlock),
> -        VMSTATE_TIMER_PTR(timer, TimerBlock),
> +        VMSTATE_PTIMER(timer, TimerBlock),
>          VMSTATE_END_OF_LIST()
>      }
>  };
>  
>  static const VMStateDescription vmstate_arm_mptimer = {
>      .name = "arm_mptimer",
> -    .version_id = 2,
> -    .minimum_version_id = 2,
> +    .version_id = 3,
> +    .minimum_version_id = 3,
>      .fields = (VMStateField[]) {
>          VMSTATE_STRUCT_VARRAY_UINT32(timerblock, ARMMPTimerState, num_cpu,
> -                                     2, vmstate_timerblock, TimerBlock),
> +                                     3, vmstate_timerblock, TimerBlock),
>          VMSTATE_END_OF_LIST()
>      }
>  };
> diff --git a/include/hw/timer/arm_mptimer.h b/include/hw/timer/arm_mptimer.h
> index b34cba0..93db61b 100644
> --- a/include/hw/timer/arm_mptimer.h
> +++ b/include/hw/timer/arm_mptimer.h
> @@ -27,12 +27,10 @@
>  
>  /* State of a single timer or watchdog block */
>  typedef struct {
> -    uint32_t count;
>      uint32_t load;
>      uint32_t control;
>      uint32_t status;
> -    int64_t tick;
> -    QEMUTimer *timer;
> +    struct ptimer_state *timer;
>      qemu_irq irq;
>      MemoryRegion iomem;
>  } TimerBlock;
> -- 
> 2.6.4
> 

Re: [Qemu-devel] [PATCH v8 1/4] hw/ptimer: Fix issues caused by the adjusted timer limit value

[Dmitry Osipenko]

06.01.2016 15:15, Peter Crosthwaite пишет:
>> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
>> index edf077c..035af97 100644
>> --- a/hw/core/ptimer.c
>> +++ b/hw/core/ptimer.c
>> @@ -34,20 +34,39 @@ static void ptimer_trigger(ptimer_state *s)
>>
>>   static void ptimer_reload(ptimer_state *s)
>>   {
>> -    if (s->delta == 0) {
>> +    uint32_t period_frac = s->period_frac;
>> +    uint64_t period = s->period;
>> +    uint64_t delta = s->delta;
>> +    uint64_t limit = s->limit;
>> +
>
> Localising these variables is out of scope of the change. I think you can
> just use s->foo and if you want to cleanup, it should be a separate
> patch.
>

Okay

>> +    if (delta == 0) {
>>           ptimer_trigger(s);
>> -        s->delta = s->limit;
>> +        delta = limit;
>>       }
>> -    if (s->delta == 0 || s->period == 0) {
>> +    if (delta == 0 || period == 0) {
>>           fprintf(stderr, "Timer with period zero, disabling\n");
>>           s->enabled = 0;
>>           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) && (limit * period < 10000)) {
>> +        period = 10000 / limit;
>> +        period_frac = 0;
>> +    }
>> +
>
> I think it should be ok to just update s->period and s->period_frac ...
>

No, then it would be irreversibly lost. What if'd decide to change the limit to 
some large value?

>>       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 + delta * period;
>> +    if (period_frac) {
>> +        s->next_event += ((int64_t)period_frac * delta) >> 32;
>>       }
>>       timer_mod(s->timer, s->next_event);
>>   }
>> @@ -82,6 +101,8 @@ 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;
>>
>>               /* We need to divide time by period, where time is stored in
>>                  rem (64-bit integer) and period is stored in period/period_frac
>> @@ -93,8 +114,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>                  backwards.
>>               */
>>
>> +            if ((s->enabled == 1) && (s->limit * period < 10000)) {
>> +                period = 10000 / s->limit;
>> +                period_frac = 0;
>> +            }
>> +
>
> ... and then this (and the local variables) become obsolete. Can get_count()
> blindly use the period and period_frac as used by ptimer_reload?
>
>>               rem = s->next_event - now;
>> -            div = s->period;
>> +            div = period;
>>
>>               clz1 = clz64(rem);
>>               clz2 = clz64(div);
>> @@ -103,13 +129,13 @@ 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 +207,6 @@ 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) {
>
> This original rate limiting code is gated on icount, so I think then
> new way should be the same.
>

Shoot :) That's second time I'm missing it. Good catch!

> Regards,
> Peter
>
>> -        limit = 10000 / s->period;
>> -    }
>> -
>>       s->limit = limit;
>>       if (reload)
>>           s->delta = limit;
>> --
>> 2.6.4
>>


-- 
Dmitry

Re: [Qemu-devel] [PATCH v8 1/4] hw/ptimer: Fix issues caused by the adjusted timer limit value

[Peter Crosthwaite]

On Wed, Jan 6, 2016 at 5:25 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> 06.01.2016 15:15, Peter Crosthwaite пишет:
>>>
>>> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
>>> index edf077c..035af97 100644
>>> --- a/hw/core/ptimer.c
>>> +++ b/hw/core/ptimer.c
>>> @@ -34,20 +34,39 @@ static void ptimer_trigger(ptimer_state *s)
>>>
>>>   static void ptimer_reload(ptimer_state *s)
>>>   {
>>> -    if (s->delta == 0) {
>>> +    uint32_t period_frac = s->period_frac;
>>> +    uint64_t period = s->period;
>>> +    uint64_t delta = s->delta;
>>> +    uint64_t limit = s->limit;
>>> +
>>
>>
>> Localising these variables is out of scope of the change. I think you can
>> just use s->foo and if you want to cleanup, it should be a separate
>> patch.
>>
>
> Okay
>
>>> +    if (delta == 0) {
>>>           ptimer_trigger(s);
>>> -        s->delta = s->limit;
>>> +        delta = limit;
>>>       }
>>> -    if (s->delta == 0 || s->period == 0) {
>>> +    if (delta == 0 || period == 0) {
>>>           fprintf(stderr, "Timer with period zero, disabling\n");
>>>           s->enabled = 0;
>>>           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) && (limit * period < 10000)) {
>>> +        period = 10000 / limit;
>>> +        period_frac = 0;
>>> +    }
>>> +
>>
>>
>> I think it should be ok to just update s->period and s->period_frac ...
>>
>
> No, then it would be irreversibly lost. What if'd decide to change the limit
> to some large value?
>

Ok makes sense.

>
>>>       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 + delta * period;
>>> +    if (period_frac) {
>>> +        s->next_event += ((int64_t)period_frac * delta) >> 32;
>>>       }
>>>       timer_mod(s->timer, s->next_event);
>>>   }
>>> @@ -82,6 +101,8 @@ 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;
>>>
>>>               /* We need to divide time by period, where time is stored
>>> in
>>>                  rem (64-bit integer) and period is stored in
>>> period/period_frac
>>> @@ -93,8 +114,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>>                  backwards.
>>>               */
>>>
>>> +            if ((s->enabled == 1) && (s->limit * period < 10000)) {
>>> +                period = 10000 / s->limit;
>>> +                period_frac = 0;
>>> +            }
>>> +

As this now needs to be kept, another note I had is it should probably
go before the block comment as the comment relates specifically to the
math below.

Regards,
Peter

>>
>>
>> ... and then this (and the local variables) become obsolete. Can
>> get_count()
>> blindly use the period and period_frac as used by ptimer_reload?
>>
>>>               rem = s->next_event - now;
>>> -            div = s->period;
>>> +            div = period;
>>>
>>>               clz1 = clz64(rem);
>>>               clz2 = clz64(div);
>>> @@ -103,13 +129,13 @@ 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 +207,6 @@ 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) {
>>
>>
>> This original rate limiting code is gated on icount, so I think then
>> new way should be the same.
>>
>
> Shoot :) That's second time I'm missing it. Good catch!
>
>
>> Regards,
>> Peter
>>
>>> -        limit = 10000 / s->period;
>>> -    }
>>> -
>>>       s->limit = limit;
>>>       if (reload)
>>>           s->delta = limit;
>>> --
>>> 2.6.4
>>>
>
>
> --
> Dmitry

Re: [Qemu-devel] [PATCH v8 2/4] hw/ptimer: Perform tick and counter wrap around if timer already expired

[Peter Crosthwaite]

On Wed, Jan 6, 2016 at 5:12 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> 06.01.2016 15:17, Peter Crosthwaite пишет:
>
>> On Tue, Jan 05, 2016 at 05:33:27AM +0300, Dmitry Osipenko wrote:
>>>
>>> ptimer_get_count() might be called while QEMU timer already been expired.
>>> In that case ptimer would return counter = 0, which might be undesirable
>>> in case of polled timer. Do counter wrap around for periodic timer to
>>> keep
>>> it distributed.
>>>
>>> In addition, there is no reason to keep expired timer tick deferred, so
>>> just perform the tick from ptimer_get_count().
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>>   hw/core/ptimer.c | 35 +++++++++++++++++++++++++++++------
>>>   1 file changed, 29 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
>>> index 035af97..96a6c7a 100644
>>> --- a/hw/core/ptimer.c
>>> +++ b/hw/core/ptimer.c
>>> @@ -85,15 +85,21 @@ static void ptimer_tick(void *opaque)
>>>
>>>   uint64_t ptimer_get_count(ptimer_state *s)
>>>   {
>>> +    int enabled = s->enabled;
>>
>>
>> Variable localisation not needed.
>>
>>>       int64_t now;
>>> +    int64_t next;
>>>       uint64_t counter;
>>> +    int expired;
>>> +    int oneshot;
>>
>>
>> Variable defs can be localised to the if (enabled) (even though now
>> in original code doesn't do that).
>>
>
> Yeah, I just tried to keep original style here.
>
>>>
>>> -    if (s->enabled) {
>>> +    if (enabled) {
>>>           now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>>> +        next = s->next_event;
>>> +        expired = (now - next >= 0);
>>> +        oneshot = (enabled == 2);
>>>           /* Figure out the current counter value.  */
>>
>>
>> This comment is now out of place.
>>
>
> Okay, will fix it.
>
>
>>> -        if (now - s->next_event > 0
>>> -            || s->period == 0) {
>>> -            /* Prevent timer underflowing if it should already have
>>> +        if (s->period == 0 || (expired && oneshot)) {
>>> +            /* Prevent one-shot timer underflowing if it should already
>>> have
>>>                  triggered.  */
>>>               counter = 0;
>>>           } else {
>>> @@ -114,12 +120,12 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>>                  backwards.
>>>               */
>>>
>>> -            if ((s->enabled == 1) && (s->limit * period < 10000)) {
>>> +            if (!oneshot && (s->limit * period < 10000)) {
>>>                   period = 10000 / s->limit;
>>>                   period_frac = 0;
>>>               }
>>>
>>> -            rem = s->next_event - now;
>>> +            rem = expired ? now - next : next - now;
>>>               div = period;
>>>
>>>               clz1 = clz64(rem);
>>> @@ -139,6 +145,23 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>>                       div += 1;
>>>               }
>>>               counter = rem / div;
>>> +
>>> +            if (expired) {
>>> +                /* Wrap around periodic counter.  */
>>> +                counter = s->delta = s->limit - counter % s->limit;
>>
>>
>> Why do you update the delta here?
>>
>
> Because we would want to schedule next tick based on current wrapped around
> counter value and not some arbitrary delta.
>

So looking at ptimer_reload(), the new schedule is done relative to
the VM clock of the when the tick was expected to hit, not the current
time. But this new delta is going to be relative to the now time and
then used to update the next tick which will happen relative to
next_event. Unless you stop or scale the timer, I don't think you need
to do delta manipulation?

>> Also can you just get ptimer_reload to do the modulo math for you? If the
>> timer is !oneshot and expired, then you call ptimer_reload anyway,
>> which will update next_event. When the expired test returns false
>> you can just reliably use the original logic involving now and next.
>>
>
> Yes, that's what I changed in V9. Have you received it?
>
> https://lists.nongnu.org/archive/html/qemu-devel/2016-01/msg00272.html
>

Just had a look.

V9 still has the modulo I think?:

+            if (expired && (counter != 0)) {
+                /* Wrap around periodic counter.  */
+                counter = s->delta = s->limit - counter % s->limit;
+            }

Regards,
Peter

>>> +            }
>>> +        }
>>> +
>>> +        if (expired) {
>>> +            if (oneshot) {
>>
>>
>> This if-else has a lot of common structure with the one above. I think
>> they could be merged.
>>
>
> That's a good suggestion, will do it in V10. Thanks.
>
>
>> Regards,
>> Peter
>>
>>> +                ptimer_tick(s);
>>> +            } else {
>>> +                /* Don't use ptimer_tick() for the periodic timer since
>>> it
>>> +                 * would reset the delta value.
>>> +                 */
>>> +                ptimer_trigger(s);
>>> +                ptimer_reload(s);
>>> +            }
>>>           }
>>>       } else {
>>>           counter = s->delta;
>>> --
>>> 2.6.4
>>>
>
>
> --
> Dmitry

Re: [Qemu-devel] [PATCH v8 2/4] hw/ptimer: Perform tick and counter wrap around if timer already expired

[Dmitry Osipenko]

06.01.2016 16:59, Peter Crosthwaite пишет:

>>>> +
>>>> +            if (expired) {
>>>> +                /* Wrap around periodic counter.  */
>>>> +                counter = s->delta = s->limit - counter % s->limit;
>>>
>>>
>>> Why do you update the delta here?
>>>
>>
>> Because we would want to schedule next tick based on current wrapped around
>> counter value and not some arbitrary delta.
>>
>
> So looking at ptimer_reload(), the new schedule is done relative to
> the VM clock of the when the tick was expected to hit, not the current
> time. But this new delta is going to be relative to the now time and
> then used to update the next tick which will happen relative to
> next_event. Unless you stop or scale the timer, I don't think you need
> to do delta manipulation?
>

Yes, I missed that next_event would be set earlier (like you described) in case 
of expired timer. Thanks for the note, will fix it.

>>> Also can you just get ptimer_reload to do the modulo math for you? If the
>>> timer is !oneshot and expired, then you call ptimer_reload anyway,
>>> which will update next_event. When the expired test returns false
>>> you can just reliably use the original logic involving now and next.
>>>
>>
>> Yes, that's what I changed in V9. Have you received it?
>>
>> https://lists.nongnu.org/archive/html/qemu-devel/2016-01/msg00272.html
>>
>
> Just had a look.
>
> V9 still has the modulo I think?:
>
> +            if (expired && (counter != 0)) {
> +                /* Wrap around periodic counter.  */
> +                counter = s->delta = s->limit - counter % s->limit;
> +            }
>

Modulo is there, I just meant that V9 changed to call ptimer_reload() on counter 
== 0. As noted above, ptimer_reload would adjust next_event, so s->delta
shouldn't be set to the wrapped around counter. However it should be set to the 
limit, since delta might been altered by ptimer_set_count.

-- 
Dmitry

Re: [Qemu-devel] [PATCH v8 4/4] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

06.01.2016 16:17, Peter Crosthwaite пишет:
> On Tue, Jan 05, 2016 at 05:33:29AM +0300, Dmitry Osipenko wrote:
>> Current ARM MPTimer implementation uses QEMUTimer for the actual timer,
>> this implementation isn't complete and mostly tries to duplicate of what
>> generic ptimer is already doing fine.
>>
>> Conversion to ptimer brings the following benefits and fixes:
>> 	- Simple timer pausing implementation
>> 	- Fixes counter value preservation after stopping the timer
>> 	- Code simplification and reduction
>>
>> Bump VMSD to version 3, since VMState is changed and is not compatible
>> with the previous implementation.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>   hw/timer/arm_mptimer.c         | 110 ++++++++++++++++++-----------------------
>>   include/hw/timer/arm_mptimer.h |   4 +-
>>   2 files changed, 49 insertions(+), 65 deletions(-)
>>
>> diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
>> index 3e59c2a..c06da5e 100644
>> --- a/hw/timer/arm_mptimer.c
>> +++ b/hw/timer/arm_mptimer.c
>> @@ -19,8 +19,9 @@
>>    * with this program; if not, see <http://www.gnu.org/licenses/>.
>>    */
>>
>> +#include "hw/ptimer.h"
>>   #include "hw/timer/arm_mptimer.h"
>> -#include "qemu/timer.h"
>> +#include "qemu/main-loop.h"
>>   #include "qom/cpu.h"
>>
>>   /* This device implements the per-cpu private timer and watchdog block
>> @@ -47,28 +48,10 @@ static inline uint32_t timerblock_scale(TimerBlock *tb)
>>       return (((tb->control >> 8) & 0xff) + 1) * 10;
>>   }
>>
>> -static void timerblock_reload(TimerBlock *tb, int restart)
>> -{
>> -    if (tb->count == 0) {
>> -        return;
>> -    }
>> -    if (restart) {
>> -        tb->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>> -    }
>> -    tb->tick += (int64_t)tb->count * timerblock_scale(tb);
>> -    timer_mod(tb->timer, tb->tick);
>> -}
>> -
>>   static void timerblock_tick(void *opaque)
>>   {
>>       TimerBlock *tb = (TimerBlock *)opaque;
>>       tb->status = 1;
>> -    if (tb->control & 2) {
>> -        tb->count = tb->load;
>> -        timerblock_reload(tb, 0);
>> -    } else {
>> -        tb->count = 0;
>> -    }
>>       timerblock_update_irq(tb);
>>   }
>>
>> @@ -76,21 +59,11 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
>>                                   unsigned size)
>>   {
>>       TimerBlock *tb = (TimerBlock *)opaque;
>> -    int64_t val;
>>       switch (addr) {
>>       case 0: /* Load */
>>           return tb->load;
>>       case 4: /* Counter.  */
>> -        if (((tb->control & 1) == 0) || (tb->count == 0)) {
>> -            return 0;
>> -        }
>> -        /* Slow and ugly, but hopefully won't happen too often.  */
>> -        val = tb->tick - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>> -        val /= timerblock_scale(tb);
>> -        if (val < 0) {
>> -            val = 0;
>> -        }
>> -        return val;
>> +        return ptimer_get_count(tb->timer);
>>       case 8: /* Control.  */
>>           return tb->control;
>>       case 12: /* Interrupt status.  */
>> @@ -100,6 +73,19 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
>>       }
>>   }
>>
>> +static void timerblock_run(TimerBlock *tb, uint64_t count, int set_count)
>> +{
>> +    if (set_count) {
>> +        if (((tb->control & 3) == 3) && (count == 0)) {
>
> Parentheses around == expressions should not be needed.
>
>> +            count = tb->load;
>> +        }
>> +        ptimer_set_count(tb->timer, count);
>> +    }
>> +    if ((tb->control & 1) && (count != 0)) {
>
> This can check against tb->load instead of count to avoid dummy
> pass of tb->load to this fn ...
>
>> +        ptimer_run(tb->timer, !(tb->control & 2));
>> +    }
>> +}
>> +
>>   static void timerblock_write(void *opaque, hwaddr addr,
>>                                uint64_t value, unsigned size)
>>   {
>> @@ -108,32 +94,34 @@ static void timerblock_write(void *opaque, hwaddr addr,
>>       switch (addr) {
>>       case 0: /* Load */
>>           tb->load = value;
>> -        /* Fall through.  */
>> -    case 4: /* Counter.  */
>> -        if ((tb->control & 1) && tb->count) {
>> -            /* Cancel the previous timer.  */
>> -            timer_del(tb->timer);
>> +        /* Setting load to 0 stops the timer.  */
>> +        if (tb->load == 0) {
>> +            ptimer_stop(tb->timer);
>>           }
>> -        tb->count = value;
>> -        if (tb->control & 1) {
>> -            timerblock_reload(tb, 1);
>> +        ptimer_set_limit(tb->timer, tb->load, 1);
>> +        timerblock_run(tb, tb->load, 0);
>> +        break;
>> +    case 4: /* Counter.  */
>> +        /* Setting counter to 0 stops the one-shot timer.  */
>> +        if (!(tb->control & 2) && (value == 0)) {
>> +            ptimer_stop(tb->timer);
>>           }
>> +        timerblock_run(tb, value, 1);
>
> ... then this would just need to be elsed.
>
>>           break;
>>       case 8: /* Control.  */
>>           old = tb->control;
>>           tb->control = value;
>> -        if (value & 1) {
>> -            if ((old & 1) && (tb->count != 0)) {
>> -                /* Do nothing if timer is ticking right now.  */
>> -                break;
>> -            }
>> -            if (tb->control & 2) {
>> -                tb->count = tb->load;
>> -            }
>> -            timerblock_reload(tb, 1);
>> -        } else if (old & 1) {
>> -            /* Shutdown the timer.  */
>> -            timer_del(tb->timer);
>> +        /* Timer mode switch requires ptimer to be stopped.  */
>
> Is it worth adding this to ptimer? It seems ptimer can now handle
> every other case of running configuration change except this one
> case.
>

Yeah, should make code cleaner as well.

>> +        if ((old & 3) != (tb->control & 3)) {
>> +            ptimer_stop(tb->timer);
>> +        }
>> +        if (!(tb->control & 1)) {
>> +            break;
>> +        }
>> +        ptimer_set_period(tb->timer, timerblock_scale(tb));
>> +        if ((old & 3) != (tb->control & 3)) {
>> +            value = ptimer_get_count(tb->timer);
>> +            timerblock_run(tb, value, 1);
>
> Is this reachable when the load value is still 0?
>
> Following on from the suggested refactor before, I think timerblock_run
> should split off the count set to a new helper. Then this is
>
> timerblock_setcount(tb, value);
> timerblock_run(tb);
>
> and the boolean arg and dummy pass of tb->load as count are unneeded.
>

What about to just inline timerblock_run? It would allow compiler to eliminate 
dead code.

-- 
Dmitry

Re: [Qemu-devel] [PATCH v8 4/4] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

06.01.2016 16:17, Peter Crosthwaite пишет:
>> +        if ((old & 3) != (tb->control & 3)) {
>> +            ptimer_stop(tb->timer);
>> +        }
>> +        if (!(tb->control & 1)) {
>> +            break;
>> +        }
>> +        ptimer_set_period(tb->timer, timerblock_scale(tb));
>> +        if ((old & 3) != (tb->control & 3)) {
>> +            value = ptimer_get_count(tb->timer);
>> +            timerblock_run(tb, value, 1);
>
> Is this reachable when the load value is still 0?
>

Yes, timer runs based on current counter value. You can load = 0 and set counter 
!= 0 that would result in one-shot tick. Hmm... I need to fix it. Thanks for 
leading question!

Ughh... just noticed that test_timer_set_oneshot_count_to_0() on real HW sets IT 
bit if prescaler != 0. Looking into it..

-- 
Dmitry