Subject: Re: some questions
To: Mihai CHELARU <>
From: Manuel Bouyer <>
List: port-xen
Date: 01/05/2006 13:43:25
On Thu, Jan 05, 2006 at 10:15:52AM +0200, Mihai CHELARU wrote:
> Hello Sirs,
> I buying a new server in a couple of days and I want to know if it's possible to do the following things (I'll use xen2 and netbsd3 as both dom0 and all domUs):
> 1) the server will be SMP with HT processors. is it possible to keep each domU on a physical CPU and each domU to use also HT (shorlty, every VM grounded to a physical CPU, while the kernel should see the 2 HT processors somehow) ?

Not with Xen2. Xen2 doens't suppport SMP in guests. Xen3 does but a lot of
work is needed in NetBSD/Xen to support SMP.

> 2) Even more, is it possible to link every VM to a virtual HT processor ?


> Should I be aware of any security issues in this case ?.

You're talking about the timing attack via the shared cache ? It's probably
possible between 2 guests, but probably harder than on a SMP system because
it's harder to get information from one guest about the other (like, what
processes are currently running)

> 3) if the server will have 2 PCI SCSI controllers is it possible to use each one for single machine (shortly, domU1 should see and use only the first controller and use it's attached disks, and domU2 the second..) ? physdev_dom0_hide should do the trick, right ?

Yes, that what's it's for. You'll have to build custom kernels with PCI support
for the domUs

> 4) is it possible to use ALTQ in xen0 kernel in order to limit the unprivileged domains ?

Yes, to a limited extent. I have plans to improve this, but there's already
so much on my todo list ...

> 5) is it possible to fix the xen networking interface names corresponding to each domU ?

Unfortunably not.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference