wip: talking about the possibles VMCSs states

docs/vmcs.md

@@ -30,3 +30,24 @@ struct vmcs_t {
 
 [^1]: it seems that the `gcc` extension `__attribute__((packed))` doesn't help
 in this case because it ruins the 8-byte alignment (according to `clangd`)
+
+## States
+
+The figure below helps to illustrate the lifecycle of a VM and its corresponding
+VMCSs.
+
+![States of a VMCS](./figs/vmcs/state.png)
+
+### Current
+
+- After the execution of the `vmptrld` instruction with the address of a given
+VMCS as its memory operand, that VMCS becomes both _active_ and **_current_**
+on the logical processor
+- At most one of the _active_ VMCSs is the **_current_** VMCS
+
+### Launch
+
+- Determines which VM-entry instruction should be used with that VMCS
+    - The `vmlaunch` instruction requires a VMCS whose _launch_ state is
+    **"clear"**
+    - Successful execution of the instruction changes the state to **"launched"**