Re: [Xen-users] Re: [Xen-devel] Re: Writing a tool for Shared Persistent Windows Boot Image

["Andrew Warfield" <andrew.warfield@xxxxxxxxxxxx>]

This should have been fixed a few months ago:

# HG changeset patch
# User wim@xxxxxxxxxxxx
# Date 1170895981 28800
# Node ID 6524e02edbeb8aebe65aa5400af4b09dfccb8729
# Parent  780f097b54c5f9161f7c6cf3f86b2bb72cc43587
[blktap] Allow HVM booting from blktap device(s)

What problems are you seeing?

a.

On 6/28/07, Daniel P. Berrange <berrange@xxxxxxxxxx> wrote:
> On Thu, Jun 28, 2007 at 12:18:47PM -0600, Jim Burnes wrote:
> > Anthony (and anyone else listening),
> >
> > I've installed Centos 5, Xen 3.1 (from the Xensource RPMs) and installed a
> > base Windows image to an LVM to test.
> >
> > The installation wen't fairly well and I resolved various issues like
> > getting the VMs to render to VNC displays properly.
> >
> > I even used LVM snapshotting to do some quick copy-on-write tests.  In that
> > configuration I've had up to 7 Windows VMs running at the same time, on
> > separate IPs, writing to LVM copy-on-write snapshots.  The only problem is
> > that LVM cow snapshots consume too much main memory.
> >
> > So I proceeded to my final test which was to replace the LVM storage with
> > QCOW storage and see how many Windows VMs I could run concurrently.  (I'm
> > trying for 12).
> >
> > The only cow tool I had was qcow-create, so I downloaded the qemu RPMs and
> > installed them.
> >
> > I used img2qcow to convert my installed Windows LVM image to the qcow base
> > image.
> > I used qcow-img to create a copy-on-write snapshot of the base image.
> > I tried to boot with this as the new storage type by specifiying:
> >
> > disk = [ 'tap:qcow:/var/lib/xen/image/winflp.img,hda1,w',
> > 'file:/var/lib/xen/install/winflp.iso,hdc:cdrom,r']
> >
> > (and other variations, by using 'hda' instead of 'hda1', using 'tap:aio'
> > instead of 'tap:qcow')
> >
> > But everytime I try to start the vm by 'xm create' it seems to create the VM
> > and the VM immediately exits, leaving hardly any trace of even booting.  I
> > tried booting directly to hard drive C: and I tried booting to the CDROM.
> > Booting to the CDROM worked fine but reported no attached hard drive.
> >
> > The only thing I see is a trace in the xend.log file which indicates that
> > xend (or the VM) is attempting to generate some sort of hotplug event for
> > tap.  Then the whole VM shuts down.
> >
> > Is there something I need to do before tap:qcow works?
> >
> > I suspect, but am having a hard time proving that either:
> >
> > (1) My version of Xen 3.1 doesn't support tap:qcow or
>
> It is not possible to use  blktap with HVM guests - there was code which tried
> to make it work, but its utterly broken[1]. In my spare time I'm trying to fix
> it, but no ETA.
>
> Dan.
> [1] it is calling APIS in XenD which no longer exist & has a try..except
>     block which silently catches & ignores the errors, so you never notice
>     that it failed.
> --
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