Re: [Xen-devel] can I boot privilleged dom like dom0 via xm create

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

Ruby,

Further to what Derek has said, I'd like to point out that what kernel you use 
never affects the privilege of the guest.

All the -xen0 kernel name means is that the kernel /can/ do dom0 stuff.  This 
is as opposed to a -xenU kernel, which has had the dom0 support removed from 
it.  Removing the dom0 support in a xenU kernel is done /only to make the 
kernel smaller/.  It doesn't have any effect on security or privilege.

Actually, most distributions seem to now supply one -xen kernel that is used 
both in dom0 and domU.

This is because, as Derek mentioned, Xen enforces the privileges of guests 
itself and doesn't have to trust their kernels.  This is different to how 
User Mode Linux works, since in that system the kernel itself enforces the 
virtual machine boundaries.  You can securely run any kernel you want in a 
domU - even one supplied by the user - because Xen will contain it.

Cheers,
Mark

> At present, there is no way to do this with xm. In the hypervisor,
> each struct domain has an is_privileged attribute (which is at present
> only set when dom0 is created at boot). You could add a domctl to
> control the setting of this bit, and then write a small C program that
> uses do_domctl from libxc to set the privilege on a domain.
>
> However, simply running two privileged domains with parallel sets of
> Xen tools is unlikely to work, for example because you will end up
> with two instances of XenStore.
>
> Regards,
>
> Derek Murray.
>
> 2008/6/13 ruby young <yangyang@xxxxxxxxxxxxxxx>:
> > Hi all,
> >     I'm using vmlinuz-2.6.18-xen0 as domU kernel and I boot it via xm
> > create. But the kernel didn't panic, it's running but all of xen tools
> > can not work. I am surprised at this.
> >     Now My question whether I can boot privilleged dom like dom0 via xm
> > create ? and how can I do it?
> >     I am looking forwards to your suggestions.
> >
> > Best wishes
> >
> >                                       Ruby Young
> >
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> >------- Yang Yang
> > Institute of Computer Architecture and System
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