[Qemu-devel] [PATCH v6 07/18] apic: Open-code timer save/restore

[Jan Kiszka]

To enable migration between accelerated and non-accelerated APIC models,
we will need to handle the timer saving and restoring specially and can
no longer rely on the automatics of VMSTATE_TIMER. Specifically,
accelerated model will not start any QEMUTimer.

This patch therefore factors out the generic bits into apic_next_timer
and uses the post-load callback to implemented model-specific logic.

Signed-off-by: Jan Kiszka <address@hidden>
---
 hw/apic.c          |   33 +++++++++++++++------------------
 hw/apic_common.c   |   41 +++++++++++++++++++++++++++++++++++++++--
 hw/apic_internal.h |    2 ++
 3 files changed, 56 insertions(+), 20 deletions(-)

diff --git a/hw/apic.c b/hw/apic.c
index 8f1d5aa..94b0841 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -527,25 +527,9 @@ static uint32_t apic_get_current_count(APICCommonState *s)
 
 static void apic_timer_update(APICCommonState *s, int64_t current_time)
 {
-    int64_t next_time, d;
-
-    if (!(s->lvt[APIC_LVT_TIMER] & APIC_LVT_MASKED)) {
-        d = (current_time - s->initial_count_load_time) >>
-            s->count_shift;
-        if (s->lvt[APIC_LVT_TIMER] & APIC_LVT_TIMER_PERIODIC) {
-            if (!s->initial_count)
-                goto no_timer;
-            d = ((d / ((uint64_t)s->initial_count + 1)) + 1) * 
((uint64_t)s->initial_count + 1);
-        } else {
-            if (d >= s->initial_count)
-                goto no_timer;
-            d = (uint64_t)s->initial_count + 1;
-        }
-        next_time = s->initial_count_load_time + (d << s->count_shift);
-        qemu_mod_timer(s->timer, next_time);
-        s->next_time = next_time;
+    if (apic_next_timer(s, current_time)) {
+        qemu_mod_timer(s->timer, s->next_time);
     } else {
-    no_timer:
         qemu_del_timer(s->timer);
     }
 }
@@ -759,6 +743,18 @@ static void apic_mem_writel(void *opaque, 
target_phys_addr_t addr, uint32_t val)
     }
 }
 
+static int apic_post_load(void *opaque, int version_id)
+{
+    APICState *s = opaque;
+
+    if (s->apic.timer_expiry != -1) {
+        qemu_mod_timer(s->apic.timer, s->apic.timer_expiry);
+    } else {
+        qemu_del_timer(s->apic.timer);
+    }
+    return 0;
+}
+
 static const MemoryRegionOps apic_io_ops = {
     .old_mmio = {
         .read = { apic_mem_readb, apic_mem_readw, apic_mem_readl, },
@@ -781,6 +777,7 @@ static const VMStateDescription vmstate_apic = {
     .version_id = APIC_VMSTATE_VERSION,
     .minimum_version_id = 3,
     .minimum_version_id_old = 1,
+    .post_load = apic_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_STRUCT(apic, APICState, 0, vmstate_apic_common,
                        APICCommonState),
diff --git a/hw/apic_common.c b/hw/apic_common.c
index 455d44c..1aeb909 100644
--- a/hw/apic_common.c
+++ b/hw/apic_common.c
@@ -95,6 +95,39 @@ void apic_deliver_nmi(DeviceState *d)
     info->external_nmi(s);
 }
 
+bool apic_next_timer(APICCommonState *s, int64_t current_time)
+{
+    int64_t d;
+
+    /* We need to store the timer state separately to support APIC
+     * implementations that maintain a non-QEMU timer, e.g. inside the
+     * host kernel. This open-coded state allows us to migrate between
+     * both models. */
+    s->timer_expiry = -1;
+
+    if (s->lvt[APIC_LVT_TIMER] & APIC_LVT_MASKED) {
+        return false;
+    }
+
+    d = (current_time - s->initial_count_load_time) >> s->count_shift;
+
+    if (s->lvt[APIC_LVT_TIMER] & APIC_LVT_TIMER_PERIODIC) {
+        if (!s->initial_count) {
+            return false;
+        }
+        d = ((d / ((uint64_t)s->initial_count + 1)) + 1) *
+            ((uint64_t)s->initial_count + 1);
+    } else {
+        if (d >= s->initial_count) {
+            return false;
+        }
+        d = (uint64_t)s->initial_count + 1;
+    }
+    s->next_time = s->initial_count_load_time + (d << s->count_shift);
+    s->timer_expiry = s->next_time;
+    return true;
+}
+
 void apic_init_reset(DeviceState *d)
 {
     APICCommonState *s = DO_UPCAST(APICCommonState, busdev.qdev, d);
@@ -122,7 +155,10 @@ void apic_init_reset(DeviceState *d)
     s->next_time = 0;
     s->wait_for_sipi = 1;
 
-    qemu_del_timer(s->timer);
+    if (s->timer) {
+        qemu_del_timer(s->timer);
+    }
+    s->timer_expiry = -1;
 }
 
 void apic_reset_common(DeviceState *d)
@@ -212,7 +248,8 @@ const VMStateDescription vmstate_apic_common = {
         VMSTATE_UINT32(initial_count, APICCommonState),
         VMSTATE_INT64(initial_count_load_time, APICCommonState),
         VMSTATE_INT64(next_time, APICCommonState),
-        VMSTATE_TIMER(timer, APICCommonState),
+        VMSTATE_INT64(timer_expiry,
+                      APICCommonState), /* open-coded timer state */
         VMSTATE_END_OF_LIST()
     }
 };
diff --git a/hw/apic_internal.h b/hw/apic_internal.h
index 2ca18d4..eaddf7f 100644
--- a/hw/apic_internal.h
+++ b/hw/apic_internal.h
@@ -92,6 +92,7 @@ struct APICCommonState {
     int64_t next_time;
     int idx;
     QEMUTimer *timer;
+    int64_t timer_expiry;
     int sipi_vector;
     int wait_for_sipi;
 };
@@ -115,6 +116,7 @@ extern const VMStateDescription vmstate_apic_common;
     DEFINE_PROP_PTR("cpu_env", cont_type, cont_var.cpu_env)
 
 void apic_report_irq_delivered(int delivered);
+bool apic_next_timer(APICCommonState *s, int64_t current_time);
 void apic_reset_common(DeviceState *d);
 int apic_init_common(SysBusDevice *d);
 
-- 
1.7.3.4