Re: [Xen-devel] Driver domains and hotplug scripts, redux

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 31 Jan 2012, Tim Deegan wrote:
> Hi, 
> 
> At 10:57 +0100 on 31 Jan (1328007457), Roger Pau Monn? wrote:
> > That's what I don't get. Booting the driver domain should be no
> > problem, because you can also have a xenbackendd running in the Dom0
> > to boot the driver domain (or maybe you want to use both Dom0 and
> > another DomU as driver domains).
> > 
> > What I don't get is what you do when you have to boot a PV DomU which
> > root HDD is on the driver domain. Dom0 needs the kernel/initrd from
> > the HDD (usually extracted using pygrub). Since the HDD is inside the
> > driver domain, Dom0 doesn't have access to that image, so there's no
> > way to extract the kernel/initrd from the Dom0. What I through is that
> > the driver domain has to run pygrub, extract the kernel/initrd, and
> > pass both files to the Dom0, but how can we pass those files? libvchan
> > seems like the best option, but I would like to head others opinions
> > about this.
> 
> You could attach to the disk image (using blkfront in dom0 and
> blkback/tap/whatever in the driver domain), run pygrub and detach.
> That's basically the same thing you have to do with a qcow image in a
> traditional dom0.

this


> Or you could use pvgrub to boot the domain, so dom0 code never has to
> touch the guets-supplied disk image or kernel.  That seems much better
> to me, but maybe it wouldn't work for some existing deployments?

It wouldn't work with guests that use grub2, I believe.

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