[Xen-users] RE: [Xen-devel] xenstore -- read UUID

[dinesh chandrasekaran <dinesh_chan8@xxxxxxxxxxx>]

Okay. will trying porting the function to xen. The reason being, I need to build a table to be maintained by the hypervisor, with some fields one of which should never change during a VMs lifetime. For example, if I chose the domain_id whose value is transient the VM's domain_id changes after reboot. That is the reason why I opted for the UUID of a domain that persists over time even after migration to another machine.

Thanks,
Dinesh C

> Date: Thu, 11 Sep 2008 15:28:32 -0700
> From: geoffrey@xxxxxxxxx
> To: dinesh_chan8@xxxxxxxxxxx
> Subject: Re: [Xen-devel] xenstore -- read UUID
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
>
> > /usr/include/uuid which means I could use this only from the use space in
> > domain-0.
> > The hypervisor doesnot include these user space libraries. How could I
> > convery the dmain->handle; the 16 byte uuid to a human readable
> > from inside the hypervisor?
>
> If you want to read the a domain uuid from user space, you can use the
> XEN_DOMCTL_getdomaininfo hypercall to get the uuid. From there, you
> can turn the uuid into a readable string. If you really want to turn
> into a readable string from within the hypervisor, then you probably
> have to port uuid_unparse to xen but i am not sure I understand why
> you would to do that from the hypervisor?
>
> geoffrey
>
>
>
> > thanks,
> > Dinesh C
> >
> >> Date: Thu, 11 Sep 2008 14:28:37 -0700
> >> From: geoffrey@xxxxxxxxx
> >> To: dinesh_chan8@xxxxxxxxxxx
> >> Subject: Re: [Xen-devel] xenstore -- read UUID
> >> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
> >>
> >> > Hi geoffrey,
> >> > the xen_domain_handle_t in the domain handle field is an
> >> > unsigned char array of size 16.
> >> > Where could the UUID be accessed from?
> >> > or how would you relate the d->handle to the domain's uuid (where d is
> >> > of
> >> > type struct domain *d).
> >> > is all the 16 entries in the d->handle clubbed together to get the
> >> > domain's
> >> > uuid?
> >> >
> >>
> >> Hi dinesh,
> >>
> >> d->handle contains the domain uuid.
> >>
> >> A uuid is a 16 byte number. Xen and libuuid store uuids as 16 byte
> >> char array. They both define typedefs (xen_domain_handle_t and uuid_t
> >> respectively) for a 16 byte char array.
> >>
> >> If you want to generate a human readable version, you can use
> >> uuid_unparse to generate a 37 character C string from the uuid_t.
> >>
> >> Hope this helps.
> >>
> >> geoffrey
> >>
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