Re: [Xen-devel] Allow tools to see the hypervisor command line.

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Wednesday 17 June 2009 17:49:41 Ian Campbell wrote:
> On Wed, 2009-06-17 at 11:42 -0400, Christoph Egger wrote:
> > On Wednesday 17 June 2009 17:32:25 Ian Campbell wrote:
> > > This is useful from tools in the same way /proc/cmdline is useful for
> > > the domain 0 kernel.
> >
> > On NetBSD Dom0, this is sysctl machdep.booted_kernel.
> > Current implementation doesn't work properly, since Xen throws away
> > the first argument at startup.
> > Is it possible to not kill it ?
>
> You mean "module /boot/netsd foo=bar baz=1" becomes just "foo=bar baz=1"
> on the command line which the kernel sees but on native netbsd it would
> be "/boot/netsd foo=bar baz=1"?

Correct. On NetBSD, the system tools accessing kernel virtual space need the
kernel name to find the correct one since the kernel can be anywere and can
have any name (though there's a default name and default place).

You can also place the linux kernel anywhere and have any name for it.
GRUB doesn't care about it, right ? (Though there's a default name and a
default place as well)

> This patch wouldn't make any difference 
> to that (I guess you are just bringing it up as an aside).

I supposed so.

> Changing Xen's behaviour here would be interesting -- Linux for example
> doesn't expect to get the extra element on the command line, not sure
> what it would do with it, similarly for other existing dom0 guests. It
> would also be inconsistent with how PV domU's are launched.

I suppose, Xen throws the first argument away for historical reasons
with the assumption that noone needs it because Linux has no use for it.

Christoph


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