Make sure all pause events are popped for resuming

libvmi · May 17, 2022 · 322c6b4 · 322c6b4
1 parent 6da9184
commit 322c6b4
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Showing 4 changed files with 41 additions and 51 deletions.
diff --git a/libvmi/driver/kvm/kvm.c b/libvmi/driver/kvm/kvm.c
@@ -993,7 +993,7 @@ kvm_pause_vm(
 {
     kvm_instance_t *kvm = kvm_get_instance(vmi);
     // already paused ?
-    if (kvm->expected_pause_count)
+    if (kvm->paused)
         return VMI_SUCCESS;
 
     // pause vcpus
@@ -1002,9 +1002,9 @@ kvm_pause_vm(
         return VMI_FAILURE;
     }
 
-    kvm->expected_pause_count = vmi->num_vcpus;
+    kvm->paused = true;
 
-    dbprint(VMI_DEBUG_KVM, "--We should receive %u pause events\n", kvm->expected_pause_count);
+    dbprint(VMI_DEBUG_KVM, "--We should receive %u pause events\n", vmi->num_vcpus);
 
     return VMI_SUCCESS;
 }
@@ -1016,54 +1016,37 @@ kvm_resume_vm(
     kvm_instance_t *kvm = kvm_get_instance(vmi);
 
     // already resumed ?
-    if (!kvm->expected_pause_count)
+    if (!kvm->paused)
         return VMI_SUCCESS;
 
-    // wait to receive pause events
-    while (kvm->expected_pause_count) {
+    // make sure that there are no unprocessed pause events
+    if (kvm_process_pending_events(vmi) == VMI_FAILURE)
+        return VMI_FAILURE;
+
+    // process pause events previously inserted into pause_events_list
+    for (unsigned int vcpu = 0; vcpu < vmi->num_vcpus; vcpu++) {
         struct kvmi_dom_event *ev = NULL;
-        unsigned int ev_id = 0;
-
-        // check pause events poped by vmi_events_listen first
-        for (unsigned int vcpu = 0; vcpu < vmi->num_vcpus; vcpu++) {
-            if (kvm->pause_events_list[vcpu]) {
-                dbprint(VMI_DEBUG_KVM, "--Removing PAUSE_VCPU event from the buffer\n");
-                ev = kvm->pause_events_list[vcpu];
-                kvm->pause_events_list[vcpu] = NULL;
-                break;
-            }
-        }
 
-        // if no pause event is waiting in the list, pop next one
-        if (!ev) {
-            if (VMI_FAILURE == kvm_get_next_event(kvm, &ev, 1000)) {
-                errprint("Failed to get next KVMi event\n");
-            }
-            if (!ev) {
-                // no new events
-                // report error
-                return VMI_FAILURE;
-            }
+        if (!kvm->pause_events_list[vcpu]) {
+            errprint("%s: Missing pause event for vcpu %u\n", __func__, vcpu);
+            return VMI_FAILURE;
         }
+
+        dbprint(VMI_DEBUG_KVM, "--Removing PAUSE_VCPU event from the buffer\n");
+        ev = kvm->pause_events_list[vcpu];
+        kvm->pause_events_list[vcpu] = NULL;
+
         // handle event
-        ev_id = ev->event.common.event;
-        switch (ev_id) {
-            case KVMI_EVENT_PAUSE_VCPU:
-                dbprint(VMI_DEBUG_KVM, "--Received VCPU pause event\n");
-                kvm->expected_pause_count--;
-                if (reply_continue(kvm, ev) == VMI_FAILURE) {
-                    errprint("%s: Fail to send continue reply", __func__);
-                    free(ev);
-                    return VMI_FAILURE;
-                }
-                free(ev);
-                break;
-            default:
-                errprint("%s: Unexpected event %u\n", __func__, ev_id);
-                free(ev);
-                return VMI_FAILURE;
+        dbprint(VMI_DEBUG_KVM, "--Sending continue reply\n");
+        if (reply_continue(kvm, ev) == VMI_FAILURE) {
+            errprint("%s: Failed to send continue reply\n", __func__);
+            free(ev);
+            return VMI_FAILURE;
         }
+        free(ev);
     }
 
+    kvm->paused = false;
+
     return VMI_SUCCESS;
 }
diff --git a/libvmi/driver/kvm/kvm_events.c b/libvmi/driver/kvm/kvm_events.c
@@ -938,8 +938,8 @@ process_single_event(vmi_instance_t vmi, struct kvmi_dom_event **event)
     return status;
 }
 
-static status_t
-process_pending_events(vmi_instance_t vmi)
+status_t
+kvm_process_pending_events(vmi_instance_t vmi)
 {
     kvm_instance_t *kvm = kvm_get_instance(vmi);
     struct kvmi_dom_event *event = NULL;
@@ -973,7 +973,7 @@ process_events_with_timeout(vmi_instance_t vmi, uint32_t timeout)
     process_single_event(vmi, &event);
 
     // make sure that all pending events are processed
-    return process_pending_events(vmi);
+    return kvm_process_pending_events(vmi);
 }
 
 status_t
@@ -1008,8 +1008,10 @@ kvm_events_listen(
      * are pending we can remove/swap the events.
      */
     if (vmi->swap_events || (vmi->clear_events && g_hash_table_size(vmi->clear_events))) {
-        vmi_pause_vm(vmi);
-        if (process_pending_events(vmi) == VMI_FAILURE) {
+        if (kvm_pause_vm(vmi) == VMI_FAILURE) {
+            return VMI_FAILURE;
+        }
+        if (kvm_process_pending_events(vmi) == VMI_FAILURE) {
             return VMI_FAILURE;
         }
 
@@ -1027,7 +1029,9 @@ kvm_events_listen(
 
         g_hash_table_foreach_remove(vmi->clear_events, clear_events_full, vmi);
 
-        vmi_resume_vm(vmi);
+        if (kvm_resume_vm(vmi) == VMI_FAILURE) {
+            return VMI_FAILURE;
+        }
     }
 
     return VMI_SUCCESS;

diff --git a/libvmi/driver/kvm/kvm_events.h b/libvmi/driver/kvm/kvm_events.h
@@ -38,6 +38,9 @@ kvm_events_init(
 void
 kvm_events_destroy(vmi_instance_t vmi);
 
+status_t
+kvm_process_pending_events(vmi_instance_t vmi);
+
 status_t
 kvm_events_listen(
     vmi_instance_t vmi,

diff --git a/libvmi/driver/kvm/kvm_private.h b/libvmi/driver/kvm/kvm_private.h
@@ -56,8 +56,8 @@ typedef struct kvm_instance {
     libkvmi_wrapper_t libkvmi;
     pthread_mutex_t kvm_connect_mutex;
     pthread_cond_t kvm_start_cond;
-    unsigned int expected_pause_count;
-    // store KVMI_EVENT_PAUSE_VCPU events poped by vmi_events_listen(vmi, 0)
+    bool paused;
+    // store KVMI_EVENT_PAUSE_VCPU events popped by vmi_events_listen(vmi, 0)
     // to be used by vmi_resume_vm()
     struct kvmi_dom_event** pause_events_list;
     // dispatcher to handle VM events in each process_xxx functions