Subject: Re: Re: Re: custom kernel (from NetBSD one)
To: None <>
From: Manuel Bouyer <>
List: port-xen
Date: 05/10/2005 14:46:12
On Tue, May 10, 2005 at 12:49:04PM +0200, Joel CARNAT wrote:
> > For PCI devices, it's equivalent, as long as there isn't interrupt routing
> > issues.
> > 
>  I don't get how cardbus is different from USB/IEEE in terms of
>  interrupting. It would be weird to have to run a domainX NetBSD to

I think an interrupt needs to be assigned to the device when it's plugged in
(but I don't know cardbus very well, I still have only PCMCIA adapters :)
For PCI devices this is done by the BIOS before the OS is loaded.

>  access my cardbus because domain0 don't know how to handle this.

If domain0 can't handle it because of a Xen issue, another
domainX won't be able to do it either.

> > Yes, as you can hide some devices from domain0 and make them available to
> > other domains. I'm not sure how this would work for the display adapter
> > and keyboard/mouse, though.
> > 
>  Display is really optionnal, my real needs would be accessing my DV/DC
>  without quitting NetBSD. This makes me think of another thing... about
>  memory use, especially available memory between domains.
>  As I understand it, domain0 get xMo for grub conf. domainX get yMo from
>  their "boot config file". But I will use domainX not that often. That
>  is to say, if I give 100% of my RAM to domain0, will domainX will be
>  able to "steal" a bit of it to run ? Or do I have to configure 80% of
>  my RAM to let domainX use the leading 20% ? This is 20% of my RAM is
>  unuseable, most of the time.

With NetBSD, and in the current state of things, another domain can't steal
memory from domain0 (and domain0 can't grab unused memory for Xen).
Xen can do this, but NetBSD doesn't know how to use this yet.

>  I know RAM is cheap, but not on laptop :)
>  This makes me think (if the previous is correct) that Xen is more a
>  "constantly run several OS on your hardware" rather than "start another
>  OS when needed without rebooting" (the same way VMware or wine can be
>  used).

Actually I use it as "constantly run several OS on your hardware" :)

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