RE: [Xen-users] How to get dom0 configuration when running in domU?

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

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Hannes Kuehnemund
> Sent: 22 May 2007 09:23
> To: Xen Users
> Subject: [Xen-users] How to get dom0 configuration when 
> running in domU?
> 
> Hi,
> 
> is there any chance to get the dom0 configuration information 
> (which is 
> available in dom0 by 'xm list --long Domain-0' or 'xm vcpu-list' in 
> general) being in a domU?
> 
> The background is, only having access to domU I'd like to know the 
> mapping of my virtual CPU's. How can I figure out if my 4 
> virtual CPU's 
> aren't assigned to one single physical CPU. This information 
> is needed 
> for sizing matters.

This information SHOULDN'T be available to the guest for security
reasons - guest shouldn't even be able to tell that it's not a physical
machine [although this is probably not to hard to do with "uname -a" or
by measuring the timing of certain operations]. I'm not sure if you can
trick around and for example read CPUID to find the APICID of the
VCPU's, for example [probably not, because that would break SMP in
guest, I think]. 

Some possible option(s) for checking this are:
1. use some sort of network protocol to get back to Dom0 (or a client
supported by Dom0). Most trivial is "ssh <dom0> xm ...".

2. Try to determine it by running variable loads on the guest - such as
run one thread, then two threads, then three, then four (etc).  If you
have fewer physical CPU's than VCPU's, then there will be a proportional
slow-down per thread when you get above the number of physical CPU's.
[That is, of course, if you don't have any other competing tasks on the
same physical CPU(s), but then on the other hand, if you have four
physical CPU's, but share them with another guest, that would amount to
the same thing as not having a "full" set of CPUs in the first place,
right?]. 

--
Mats

> 
> Thanks,
>    Hannes
> 
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