[qubes-devel] Using xen-netfront in dom0

[Rafal Wojtczuk]

Hello,
In xen-netfront.c, there is an explicit check if we are running in dom0, and
if so, skip initialization:
http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=blob;f=drivers/net/xen-netfront.c;h=ee7465a7a2a9fa563f44a470bdad1911e175d1ad;hb=xen/stable-2.6.32.x#l1807

But if using a driver domain (with a NIC assigned), then definitely there is
a need to run xen-netfront in dom0. In fact, commenting out the
xen_initial_domain() check makes it work fine with a driver domain.

Is there any reason for this check, besides obviously false assumption
"nobody needs it in dom0" ? On a related note, there seems to be no such
check in xen-blkfront.c.

If there are no disadvantages, I would vote for removal of the
xen_initial_domain() check; otherwise, can we have a module parameter
"allow_dom0" ?

Regards,
Rafal Wojtczuk
The Qubes OS Project
http://qubes-os.org




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[Jeremy Fitzhardinge]

On 04/19/2010 01:26 AM, Rafal Wojtczuk wrote:
> Is there any reason for this check, besides obviously false assumption
> "nobody needs it in dom0" ? On a related note, there seems to be no such
> check in xen-blkfront.c.
>
> If there are no disadvantages, I would vote for removal of the
> xen_initial_domain() check; otherwise, can we have a module parameter
> "allow_dom0" ?
>

No, I think its probably fine to remove the check. Presumably if the
driver is modular it would never get loaded in a normal dom0 case
anyway? And in the non-modular case, an initialized but unused driver
shouldn't take much memory (and if it does, that should be fixed).

J