Fedora xen - Sep 2008 - problem with virtual interface in DomU

hi,

I finally achieve a goal to start a para-VM with xen. But i still experience
problem with networking inside the vm (domU).
There are no network interface shown. Maybe kernel module is not loaded for
the emulated NIC.
In domU i''m only able to see loopback interface. But, in dom0 i can see
all
bridge interface and networking is OK.
Can someone help me ?

thanks.

-- 
Guillaume

2008/9/15 lamont cranston <l.cranston@gmail.com>
>
> 1) verify that the virtualization extensions are turned on in the BIOS (in
my case, a HP prolient server, the selection was actually named
"virtualization")
It is not an HVM "build" so, i tought virtualization extensions are
useless  ? And i don''t have intel-VT on my system.
> 2) when you get to the end of your install of the guest OS, you should have
the option to "share" the network device
   I did not use any wizard to create the vm (i made a copy of an
actual system to an image file, and create the "xm" config file)
> 3) easiest way to verify the guest IP is to ask the guest - you can reason
it out from the host ifconfig, but just asking the guest is a lot simplier and
just "feels" right :)
I''m not so good in English, what do you mean ? :-D

--
Guillaume

>> It is not an HVM "build" so, i tought virtualization
extensions are
>> useless  ? And i don''t have intel-VT on my system.
>
> That may be the entire problem.
> My understanding is that the paravirtualized kernel needs those extensions
> so that the supervisor calls do not have to go through the hypervisor.
For me it wasn''t =) !
For my knowledge, HVM extension was needed by xen only for
fully-virtualized OS. (like Microsoft OS and other closed source OS ;
because no modification can''t be made to their kernel to make them
aware of "xen".). But maybe i''m wrong !
And if you''re right, it will explain why networking don''t work
(and
will never on my system)
    --> but keep in mind that xen exist a "long time" before hvm
extension do. And I thought that other people made networking works in
their xen VM. So, I tought that i can get rid of this problem without
hvm set on.

Someone can light me more about it ?


thanks

-- 
Guillaume

On Tue, 16 Sep 2008, Guillaume wrote:
>>> It is not an HVM "build" so, i tought virtualization
extensions are
>>> useless  ? And i don''t have intel-VT on my system.
>>
>> That may be the entire problem.
>> My understanding is that the paravirtualized kernel needs those
extensions
>> so that the supervisor calls do not have to go through the hypervisor.
> For me it wasn''t =) !
> For my knowledge, HVM extension was needed by xen only for
> fully-virtualized OS. (like Microsoft OS and other closed source OS ;
> because no modification can''t be made to their kernel to make them
> aware of "xen".). But maybe i''m wrong !
> And if you''re right, it will explain why networking don''t
work (and
> will never on my system)
>    --> but keep in mind that xen exist a "long time" before
hvm
> extension do. And I thought that other people made networking works in
> their xen VM. So, I tought that i can get rid of this problem without
> hvm set on.
>
> Someone can light me more about it ?
I agree that things have gotten confusing in area of virtualisation.
This is what I understand:

- Xen hypervisor for para_virt guests does not need HVM. Problem here is
   that Fedora 8 is the last release to support this setup on x86_64, though
   work is in progress to add this support to Fedora 9/10.
   Para_virt guests are booted via kernel= and rootfs images, or via pygrub,
   which is just a wrapper for grabbing kernel from bootable disk images.

- Qemu is a software emulator for various architectures including PC hardware.
   It requires no HVM instructions, but it can use them if they exist via
   the kernel "kvm" code. This is how Fedora9 does its VM''s
via the libvirt
   and virt-install. This does NOT not use or require a xen hypervisor.

- Xenner is a software emulation for the Xen hypervisor. It requires HVM
   because it uses the kernel "kvm" code. The idea behind Xenner is
that
   you can run VM''s based on kernel-xen kernels (eg migration from
Fedora8)

These are the main virtualisation techniques used in Fedora. There are
others, such as VirtualBox/Vmx, lguest, uml, virtuoso, openvz, and many
more. See http://virt.kernelnewbies.org/TechComparison

Paul

On Mon, 15 Sep 2008, Guillaume wrote:
> I finally achieve a goal to start a para-VM with xen. But i still
> experience problem with networking inside the vm (domU).
> There are no network interface shown. Maybe kernel module is not loaded
> for the emulated NIC.
> In domU i''m only able to see loopback interface. But, in dom0 i
can see
> all bridge interface and networking is OK.
> Can someone help me ?
You are probably re-using the initrd from the dom0 to use in a guest.

You need to create a new initrd for the domU guests using mkinitrd
--preload=xenblk --with=xennet. Or if your image boots, you might
get away with just ''modprobe xennet''.

See:

http://www.mail-archive.com/fedora-xen@redhat.com/msg00609.html

Paul

2008/9/16 Paul Wouters <paul@xelerance.com>:
> On Mon, 15 Sep 2008, Guillaume wrote:
>
>> I finally achieve a goal to start a para-VM with xen. But i still
>> experience problem with networking inside the vm (domU).
>> There are no network interface shown. Maybe kernel module is not loaded
>> for the emulated NIC.
>> In domU i''m only able to see loopback interface. But, in dom0
i can see
>> all bridge interface and networking is OK.
>> Can someone help me ?
>
> You are probably re-using the initrd from the dom0 to use in a guest.
>
> You need to create a new initrd for the domU guests using mkinitrd
> --preload=xenblk --with=xennet. Or if your image boots, you might
> get away with just ''modprobe xennet''.
 Yes i use a modified initrd to support disk drivers (where I
specified "xenblk" ), but no xennet. I''ll test it tomorrow
but im sure
it will works !
thanks


-- 
Guillaume