RE: [Xen-users] Determine which dom0 from within domU

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Fong Vang
> Sent: 19 May 2007 20:29
> To: Xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Determine which dom0 from within domU
> 
> Is it possible determine which dom0 is running a domU from 
> within the domU? 

I'm not sure exactly what you're asking, but I'm pretty sure whichever
interpretation reasonably imaginable for your question, the answer is
the same: "No". 

I can imagine that you're asking "What version of Linux is running in
Dom0", or "Which physical machine Dom0 is running on", and if I spent a
few more minutes, I could probably come up with a few other variations
of the question. 

Aside from things that can be found out through for example CPUID [CPU
features, CPU brand] and RDTSC [clock-speed] - although this can not be
wholly trusted in a virtual machine, certainly not in a HVM domain [1],
there's no way for the guest to find out (much) about the hardware that
it's running on top of. Neither is it able to enquire about the Dom0
software in any meaningfull way. 

All of this is protected for security reasons. 

If you really want to "know" things like this, the best solution is
probably to have some sort of local server that you can access via a
known name/address (e.g. if you send a message to 10.0.0.100, you get a
reply back of whatever information you wanted to find out). This server
would either run within Dom0, or on a separate domain that is updated by
Dom0 (e.g. every second you scan the "xm list" and update the server, or
add some script to for example "xm create"). 

If you explain what you actually aim to achieve, it would be easier to
answer your question with a less hypothetical and more concrete answer. 

[1] I could modify the hypervisor to say "Intel" instead of "AMD" on my
VM, should I wish to, although that isn't really meaningfull. There are
other changes to the CPUID information that HVM does: Hiding features
that aren't "allowed", such as hiding the 64-bit (LongMode) flag for
guests when the hypervisor is 32-bit - it is not meaningfull for the
guest to see a 64-bit flag on a hypervisor that won't be able to run
64-bit. 

--
Mats
> 
> 



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