A confidential guest reset involves closing the old virtual machine KVM file
descriptor and opening a new one. Since its a new KVM fd, PIT needs to be
reinitialized again. This is done with the help of a notifier which is invoked
upon KVM vm file desciptor change during confidential guest reset process.

Some code refactoring is performed so that common operations for init and reset
are moved into a helper function.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 hw/i386/kvm/i8254.c | 84 ++++++++++++++++++++++++++++-----------------
 1 file changed, 53 insertions(+), 31 deletions(-)

diff --git a/hw/i386/kvm/i8254.c b/hw/i386/kvm/i8254.c
index 14b78f30a8..0b741464d9 100644
--- a/hw/i386/kvm/i8254.c
+++ b/hw/i386/kvm/i8254.c
@@ -52,6 +52,8 @@ struct KVMPITState {
     LostTickPolicy lost_tick_policy;
     bool vm_stopped;
     int64_t kernel_clock_offset;
+
+    NotifierWithReturn kvmpit_vmfd_change_notifier;
 };
 
 struct KVMPITClass {
@@ -60,6 +62,43 @@ struct KVMPITClass {
     DeviceRealize parent_realize;
 };
 
+static void do_pit_initialize(KVMPITState *s, Error **errp)
+{
+    struct kvm_pit_config config = {
+        .flags = 0,
+    };
+    int ret;
+
+    ret = kvm_vm_ioctl(kvm_state, KVM_CREATE_PIT2, &config);
+    if (ret < 0) {
+        error_setg(errp, "Create kernel PIC irqchip failed: %s",
+                   strerror(-ret));
+        return;
+    }
+    switch (s->lost_tick_policy) {
+    case LOST_TICK_POLICY_DELAY:
+        break; /* enabled by default */
+    case LOST_TICK_POLICY_DISCARD:
+        if (kvm_check_extension(kvm_state, KVM_CAP_REINJECT_CONTROL)) {
+            struct kvm_reinject_control control = { .pit_reinject = 0 };
+
+            ret = kvm_vm_ioctl(kvm_state, KVM_REINJECT_CONTROL, &control);
+            if (ret < 0) {
+                error_setg(errp,
+                           "Can't disable in-kernel PIT reinjection: %s",
+                           strerror(-ret));
+                return;
+            }
+        }
+        break;
+    default:
+        error_setg(errp, "Lost tick policy not supported.");
+        return;
+    }
+
+    return;
+}
+
 static void kvm_pit_update_clock_offset(KVMPITState *s)
 {
     int64_t offset, clock_offset;
@@ -166,6 +205,16 @@ static void kvm_pit_put(PITCommonState *pit)
     }
 }
 
+static int kvmpit_post_vmfd_change(NotifierWithReturn *notifier,
+                                   void *data, Error** errp)
+{
+    KVMPITState *s = container_of(notifier, KVMPITState,
+                                  kvmpit_vmfd_change_notifier);
+
+    do_pit_initialize(s, errp);
+    return 0;
+}
+
 static void kvm_pit_set_gate(PITCommonState *s, PITChannelState *sc, int val)
 {
     kvm_pit_get(s);
@@ -241,49 +290,22 @@ static void kvm_pit_realizefn(DeviceState *dev, Error **errp)
     PITCommonState *pit = PIT_COMMON(dev);
     KVMPITClass *kpc = KVM_PIT_GET_CLASS(dev);
     KVMPITState *s = KVM_PIT(pit);
-    struct kvm_pit_config config = {
-        .flags = 0,
-    };
-    int ret;
 
     if (!kvm_check_extension(kvm_state, KVM_CAP_PIT_STATE2) ||
         !kvm_check_extension(kvm_state, KVM_CAP_PIT2)) {
         error_setg(errp, "In-kernel PIT not available");
     }
 
-    ret = kvm_vm_ioctl(kvm_state, KVM_CREATE_PIT2, &config);
-    if (ret < 0) {
-        error_setg(errp, "Create kernel PIC irqchip failed: %s",
-                   strerror(-ret));
-        return;
-    }
-    switch (s->lost_tick_policy) {
-    case LOST_TICK_POLICY_DELAY:
-        break; /* enabled by default */
-    case LOST_TICK_POLICY_DISCARD:
-        if (kvm_check_extension(kvm_state, KVM_CAP_REINJECT_CONTROL)) {
-            struct kvm_reinject_control control = { .pit_reinject = 0 };
-
-            ret = kvm_vm_ioctl(kvm_state, KVM_REINJECT_CONTROL, &control);
-            if (ret < 0) {
-                error_setg(errp,
-                           "Can't disable in-kernel PIT reinjection: %s",
-                           strerror(-ret));
-                return;
-            }
-        }
-        break;
-    default:
-        error_setg(errp, "Lost tick policy not supported.");
-        return;
-    }
-
+    do_pit_initialize(s, errp);
     memory_region_init_io(&pit->ioports, OBJECT(dev), NULL, NULL, "kvm-pit", 4);
 
     qdev_init_gpio_in(dev, kvm_pit_irq_control, 1);
 
     qemu_add_vm_change_state_handler(kvm_pit_vm_state_change, s);
 
+    s->kvmpit_vmfd_change_notifier.notify = kvmpit_post_vmfd_change;
+    kvm_vmfd_add_change_notifier(&s->kvmpit_vmfd_change_notifier);
+
     kpc->parent_realize(dev, errp);
 }
 
-- 
2.42.0