[CentOS] xm mem-set on an F11 xen guest

I just tried to change the memory for my F11 xen guest from 512 to 1024. 
After executing:

xm mem-set workstation 1024

xm list shows the memory still being 512.  Anyone else see this behavior 
before?  I tried other values as well - but the memory is still what it 
was when I created the VM...

I'm running CentOS 5.4 on an i386...

Scot P. Floess
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