title: segment limit check in AMD 64-bit mode
body: <p>I am writing my own OS for 64bit processors and I am stuck with the problem of general protection. My OS will not rely on page fault to implement user space protection mechanism, so I found there is a way to do it with segment limit checking:</p>
  
  <p>This presentation from VMWare </p>
  
  <p><a href="http://download3.vmware.com/vmworld/2005/pac346.pdf" rel="nofollow">http://download3.vmware.com/vmworld/2005/pac346.pdf</a></p>
  
  <p>on page 20 says:</p>
  
  <blockquote>
    <ul>
    <li><p>Initial AMD64 architecture did not include segmentation in 64-bit mode</p>
    
    <ul>
    <li>Segmentation also missing from EMT64T</li>
    </ul>
    
    <p>How do we protect the VMM ?</p>
    
    <ul>
    <li>64-bit guest support requires additional hardware assitance</li>
    <li>Segment limit checks available in 64-bit mode on newer AMD processors</li>
    </ul></li>
    </ul>
  </blockquote>
  
  <p>Now, I have the newer AMD processor model and my question is how do I achieve limit segment limit check on AMD processor in 64-bit (long) mode ? I have downloaded the Sep 2011 version  (lastest) of developer's manual and I can't find how to do this in any place, please help.</p>