Changes between Version 19 and Version 20 of VirtualBox architecture

Timestamp:

Nov 17, 2006 11:37:32 AM (17 years ago)

Author:

jose

Comment:

--

VirtualBox architecture

@@ -40 +40 @@
 
 As said above, from the perspective of the host OS, a virtual machine is just another process. The host OS does not need much tweaking to support virtualization.
+Even though there is a ring-0 driver that must be loaded in the host OS for !VirtualBox to work, this ring driver does less than you may think. It is only needed for a few specific tasks, such as:
 
-When a VM is running, from your processor's point of view, your computer can be in one of several states (the following will require a good understanding of the x86 ring architecture): 
+ * allocating physical memory for the VM;
+
+ * saving and restoring CPU registers and descriptor tables when a host interrupt occurs while a guest's ring-3 code is executing (e.g. when the host OS wants to reschedule); 
+
+ * when switching from host ring-3 to guest context;
+
+ * enable or disable VT-x etc. support.
+
+Most importantly, the host's ring-0 driver does ''not'' mess with your OS's scheduling or process management. The entire guest OS, including its own hundreds of processes, is only scheduled when the host OS gives the VM process a timeslice. 
+
+After a VM has been started, from your processor's point of view, your computer can be in one of several states (the following will require a good understanding of the x86 ring architecture): 
 
  1. Your CPU can be '''executing host ring-3 code''' (e.g. from other host processes), or '''host ring-0 code,''' just as it would be if !VirtualBox wasn't running.
@@ -60 +71 @@
    * ring 0 (which is !VirtualBox code). This guest-context ring-0 code is also often called a '''"hypervisor".'''
 
-Finally, there is also a ring-0 driver that must be loaded in the host OS for !VirtualBox to work. However, this ring-0 driver does less than you may think. It is only needed for a few specific tasks, such as:
-
- * allocating physical memory for the VM;
-
- * saving and restoring CPU registers and descriptor tables when a host interrupt occurs while a guest's ring-3 code is executing (e.g. when the host OS wants to reschedule); 
-
- * when switching from host ring-3 to guest context;
-
- * enable or disable VT-x etc. support.
-
-Most importantly, the host's ring-0 driver does ''not'' mess with your OS's scheduling or process management. The entire guest OS, including its own hundreds of processes, is only scheduled when the host OS gives the VM process a timeslice. 
-
 
 == Intel VT-x ("Vanderpool") support ==