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[Xen-devel] xen questions


I'm new to Xen and have a couple of questions:

1) I'm having trouble getting xenctl to work. I'm getting the following
error message: "Exception in thread "main" java.lang.NoClassDefFoundError:
org/xml/sax/XMLReader". I've installed jdk-1.4.2 into
/usr/local/jdk-1.4.2, and ant into /usr/local/ant. 

2) I'm looking for a way to intercept system calls within the guest O/S
using the Xen VMM (i.e. when a user-mode application makes a system call,
I want to intercept it and do something with it before it gets to the
kernel of the guest O/S). 

If I understand things correctly, the SYSCALL_VECTOR is filled into
a trap_info table by the guest O/S, and passed to xen via a
HYPERVISOR_set_trap_table() call. I would expect that when a trap occurs,
Xen looks up the trap number, consults the current trap_table, and
executes the trap. But, I'm having trouble finding that code -- can
someone point me in the right direction?

3) What is the "fast_trap" mechanism? I assume it's an optimization of
Xen's normal trap processing? I'm assuming that I'll have to turn off the
fast_trap for system calls in order to accomplish #2 above?

Scott Baker, University of Arizona 

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