
%         Registration                UML and the Intel VT extensions         
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%  [2]Register/Submit Proposal Jeff Dike (jdike@addtoit.com)                  
                                                                              
Intel has added virtualization extensions (VT) 
to the x86 architecture. It adds a new set of  
rings, guest rings 0 through 3, to the         
traditional rings, which are now called the    
host rings.                                    

User-mode Linux (UML) is in the process of     
being enhanced to make use of these extensions 
for greater performance. It will run in guest  
ring 0, gaining the ability to directly        
receive software interrupts. This will allow   
it to handle process system calls without      
needing assistance from the host kernel, which 
will let UML handle system calls at hardware   
speed.                                         

In spite of running in a ring 0, UML will      
appear to remain in userspace, making system   
calls to the host kernel and receiving signals 
from it. So, it will retain its current        
manageability, while getting a performance     
boost from its use of the hardware.            

