qdev: Introduce lost tick policy property

Potentially tick-generating timer devices will gain a common property:
lock_tick_policy. It allows to encode 4 different ways how to deal with
tick events the guest did not process in time:

discard - ignore lost ticks (e.g. if the guest compensates for them
          already)
delay   - replay all lost ticks in a row once the guest accepts them
          again
merge   - if multiple ticks are lost, all of them are merged into one
          which is replayed once the guest accepts it again
slew    - lost ticks are gradually replayed at a higher frequency than
          the original tick

Not all timer device will need to support all modes. However, all need
to accept the configuration via this common property.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 69 insertions, 0 deletions

diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index c98219ad26..028bee7da6 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -885,6 +885,55 @@ PropertyInfo qdev_prop_macaddr = {
     .set   = set_generic,
 };
 
+
+/* --- lost tick policy --- */
+
+static const struct {
+    const char *name;
+    LostTickPolicy code;
+} lost_tick_policy_table[] = {
+    { .name = "discard", .code = LOST_TICK_DISCARD },
+    { .name = "delay", .code = LOST_TICK_DELAY },
+    { .name = "merge", .code = LOST_TICK_MERGE },
+    { .name = "slew", .code = LOST_TICK_SLEW },
+};
+
+static int parse_lost_tick_policy(DeviceState *dev, Property *prop,
+                                  const char *str)
+{
+    LostTickPolicy *ptr = qdev_get_prop_ptr(dev, prop);
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(lost_tick_policy_table); i++) {
+        if (!strcasecmp(str, lost_tick_policy_table[i].name)) {
+            *ptr = lost_tick_policy_table[i].code;
+            break;
+        }
+    }
+    if (i == ARRAY_SIZE(lost_tick_policy_table)) {
+        return -EINVAL;
+    }
+    return 0;
+}
+
+static int print_lost_tick_policy(DeviceState *dev, Property *prop, char *dest,
+                                  size_t len)
+{
+    LostTickPolicy *ptr = qdev_get_prop_ptr(dev, prop);
+
+    return snprintf(dest, len, "%s", lost_tick_policy_table[*ptr].name);
+}
+
+PropertyInfo qdev_prop_losttickpolicy = {
+    .name  = "lost_tick_policy",
+    .type  = PROP_TYPE_LOSTTICKPOLICY,
+    .size  = sizeof(LostTickPolicy),
+    .parse = parse_lost_tick_policy,
+    .print = print_lost_tick_policy,
+    .get   = get_generic,
+    .set   = set_generic,
+};
+
 /* --- pci address --- */
 
 /*
@@ -1127,6 +1176,12 @@ void qdev_prop_set_macaddr(DeviceState *dev, const char *name, uint8_t *value)
     qdev_prop_set(dev, name, value, PROP_TYPE_MACADDR);
 }
 
+void qdev_prop_set_losttickpolicy(DeviceState *dev, const char *name,
+                                  LostTickPolicy *value)
+{
+    qdev_prop_set(dev, name, value, PROP_TYPE_LOSTTICKPOLICY);
+}
+
 void qdev_prop_set_ptr(DeviceState *dev, const char *name, void *value)
 {
     qdev_prop_set(dev, name, &value, PROP_TYPE_PTR);
diff --git a/hw/qdev.h b/hw/qdev.h
index c9572a546c..364e91def7 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -158,6 +158,7 @@ enum PropertyType {
     PROP_TYPE_UINT64,
     PROP_TYPE_TADDR,
     PROP_TYPE_MACADDR,
+    PROP_TYPE_LOSTTICKPOLICY,
     PROP_TYPE_DRIVE,
     PROP_TYPE_CHR,
     PROP_TYPE_STRING,
@@ -307,6 +308,7 @@ extern PropertyInfo qdev_prop_string;
 extern PropertyInfo qdev_prop_chr;
 extern PropertyInfo qdev_prop_ptr;
 extern PropertyInfo qdev_prop_macaddr;
+extern PropertyInfo qdev_prop_losttickpolicy;
 extern PropertyInfo qdev_prop_drive;
 extern PropertyInfo qdev_prop_netdev;
 extern PropertyInfo qdev_prop_vlan;
@@ -367,6 +369,9 @@ extern PropertyInfo qdev_prop_pci_devfn;
     DEFINE_PROP(_n, _s, _f, qdev_prop_drive, BlockDriverState *)
 #define DEFINE_PROP_MACADDR(_n, _s, _f)         \
     DEFINE_PROP(_n, _s, _f, qdev_prop_macaddr, MACAddr)
+#define DEFINE_PROP_LOSTTICKPOLICY(_n, _s, _f, _d) \
+    DEFINE_PROP_DEFAULT(_n, _s, _f, _d, qdev_prop_losttickpolicy, \
+                        LostTickPolicy)
 
 #define DEFINE_PROP_END_OF_LIST()               \
     {}
@@ -389,6 +394,8 @@ void qdev_prop_set_vlan(DeviceState *dev, const char *name, VLANState *value);
 int qdev_prop_set_drive(DeviceState *dev, const char *name, BlockDriverState *value) QEMU_WARN_UNUSED_RESULT;
 void qdev_prop_set_drive_nofail(DeviceState *dev, const char *name, BlockDriverState *value);
 void qdev_prop_set_macaddr(DeviceState *dev, const char *name, uint8_t *value);
+void qdev_prop_set_losttickpolicy(DeviceState *dev, const char *name,
+                                  LostTickPolicy *value);
 /* FIXME: Remove opaque pointer properties.  */
 void qdev_prop_set_ptr(DeviceState *dev, const char *name, void *value);
 void qdev_prop_set_defaults(DeviceState *dev, Property *props);
diff --git a/qemu-common.h b/qemu-common.h
index 6ab7dfb1b9..8b69a9eea5 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -250,6 +250,13 @@ typedef struct QEMUSGList QEMUSGList;
 
 typedef uint64_t pcibus_t;
 
+typedef enum LostTickPolicy {
+    LOST_TICK_DISCARD,
+    LOST_TICK_DELAY,
+    LOST_TICK_MERGE,
+    LOST_TICK_SLEW,
+} LostTickPolicy;
+
 void tcg_exec_init(unsigned long tb_size);
 bool tcg_enabled(void);