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RE: [Xen-devel] Xen help

To: Derek Riley <derek.riley@xxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-devel] Xen help
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Mon, 10 Aug 2009 08:50:04 -0700 (PDT)
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Hi Derek --

I think perhaps the problem is that your goal (at least
as I interpret it) is not possible.  The Xen hypervisor
doesn't have any way of writing to a file.  And as
far as I know, there is no way to make a hypercall from
"user space", only from the kernel of a paravirtualized
OS.  It *is* possible for an xm command executed as root
to provoke (via ioctl??) a hypercall from dom0 OS kernel
to pass a buffer, for Xen to fill in information to that
buffer, and for an OS kernel to put that buffer someplace
that could be read by a user process.  But that doesn't
sound like it would meet your goal.

If this is close enough, a key file is


and a recent patch that plumbs an xm command from
the linux command line through to xc.c is at


I'm afraid I can't help much with all the python code
though.  I've mostly mimicked code written by others
and debugged it until it worked.

Hope that points you in the right direction!

-----Original Message-----
From: Derek Riley [mailto:derek.riley@xxxxxxxxxxxxxxxxxxx]
Sent: Monday, August 10, 2009 7:49 AM
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Xen help

I have posted to this list several times re-iterating the same problem (trying 
to figure out an API mechanism between Xen and the user space), and I haven't 
heard much from you guys.  

Could someone at least point me to the file(s) that handle the API 
communication between Xen and XM?  Ideally, I would like to find a way to 
read/write to a file/device from within the scheduler, but no one has said 
anything useful about how to accomplish this.  

I apologize for the repeated attempts to get the same information, but I know 
there are people on this list who could help me, or at least point me in the 
right direction.  Any help is appreciated.  Thanks

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