Re: Xen boot failures with disks >16K (tap device issues)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sun, Mar 20, 2011 at 01:57:00AM -0700, David Hopper wrote:
> Hi all, I have a very odd condition with this NetBSD-current dom0 / Xen 
> 3.3.2nb1 in trying to start up Red Hat 6 domU instances.  I may need help 
> understanding if I'm missing some virtual block devices in the domU based on 
> the symptoms below, or if this could be a dom0 or script issue-- but the tap 
> device will not connect.
> 
> I cannot start a VM when attaching raw images larger than 16K, and I cannot 
> boot any method other than file: (any size qcow fails to boot as well).  It 
> took some trial-and-error to find the 16K threshold-- needless to say the 
> working images aren't very useful to me.
> 
> The disk definition in vm.install:  'file:/vnod/vm/vm.img,xvda,w'  (also 
> tried tap:qcow).
> 
> # qemu-img create -f raw ./vm.img 16K  <== 16 kilobyte image works
> Formatting './vm.img', fmt=raw size=16384 
> # xm create -c vm.install
> [ boots normally ]

Are you using a HVM domU, or a PV one ?
The disk definition looks like a PV one, but you're also talking about
tap(4) which is used only by HVM guests.

I suspect qemu-img creates a sparse file, which is not supported
by NetBSD's PV backend. qcow is also not supported.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--