Xen project Mailing List

I'm using Xen unstable 4.8 manually compiled on debian , I create a debian netinst guest using the following config file and then just use save/restore, after restoring a machine kernel hangout task happens.

We've test it With Xen 4.7 manually compiled on ubuntu 14.04 and the same thing happened. the guest VM was ubuntu 14.04 with GUI, after restoring we were able to move the mouse but the VM was crashed.

Also, the same kernel hangout task happened on CentOS (also its kernel is 2.6...) and with Xen 4.2.

These is important to note that after creating VMs using a raw image file created with both "qemu-img" and "dd" the problem solved and save/restore is working properly.

It seems there is a problem related to LVM.


builder = "hvm"
memory = 1024
vcpus = 2
name = "debian64"
vif = [ 'bridge=xenbr0' ]
disk = [
        'file:/dev/vg0/debian64_clone.img,xvda,rw',
        'file:/home/lisbeth/src/debian-8.5.0-amd64-netinst.iso,xvdc:cdrom,r'
       ]
 
boot = "c"

On Thu, Aug 11, 2016 at 7:48 PM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:

On Wed, Aug 10, 2016 at 02:24:09PM +0100, George Dunlap wrote:
> On Wed, Aug 10, 2016 at 12:11 PM, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
> > On Sun, Aug 07, 2016 at 07:51:14PM +0430, Cendrin Sa wrote:
> >> Hi,
> >> I was searching a way to clone a machine using both memory and disk
> >> approach.
> >> I checked xen save/restore but after restoring, I can only work some
> >> seconds with my machine and it will crash with the_kernel_task_hang_up.
> >> using an script* to clone a machine is not working either.
> >> so is it a bug or something or I'm cloning the wrong way?
> >
> > Hello,
> >
> > I've not tried to perform cloning myself, but I have a little script to
> > perform VM checkpoints (so that you can restore the VM to any given point in
> > time). It's based on FreeBSD so it uses ZFS, but it should work with LVM
> > also if you replace it with the appropriate runes. AFAICT it should be quite
> > easy to expand it to also do VM cloning. This is transparent from a VM point
> > of view.
>
> FWIW on a recent version of Xen-unstable, "xl save -c" appears to be
> broken, at least with me CentOS 6 VM. If I do "xl save" then "xl
> restore", everything works fine; but if I do "xl save -c", then the
> save appears to work as normal, and after it's done the guest console
> has output similar to the output it has when restoring, but processes
> which access the disk hang, and in 2 minutes I get "hung process"
> output as Cendrin described.
>
> I do get some warning messages though:
>
> Using NULL legacy PIC
> WARNING: g.e. still in use!
> WARNING: leaking g.e. and page still in use!
> WARNING: g.e. still in use!
> WARNING: leaking g.e. and page still in use!
> WARNING: g.e. still in use!
> WARNING: leaking g.e. and page still in use!
> Changing capacity of (202, 0) to 4194288 sectors
>
> This is the stock CentOS 6.6 kernel: 2.6.32-504.16.2.el6.x86_64
>

It looks like the guest kernel is trying to free up all the grant
references.

In the case of xl save -c my impression is that it shouldn't be doing
that because the suspend is supposed to be canceled from guest's PoV.

See comment in xenctrl.h for xc_domain_resume.

Also related: 8903a7a5f6a47cc40c1c204a1cc28b0030b04486

Wei.

> -George

Re: [Xen-devel] Save/Restore is not working properly