Re: Save/Restore is not working properly

[Cendrin Sa <cendrinoe@gmail.com>]

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I used save without any option when my VM was in running state, save won't
work if I pause a VM.


On Sat, Aug 13, 2016 at 11:04 AM, Cendrin Sa <cendrinoe@gmail.com> wrote:

>
>    - 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.
>
>
>    1.
>    2. builder = "hvm"
>    3. memory = 1024
>    4. vcpus = 2
>    5. name = "debian64"
>    6. vif = [ 'bridge=xenbr0' ]
>    7. disk = [
>    8.         'file:/dev/vg0/debian64_clone.img,xvda,rw',
>    9.         'file:/home/lisbeth/src/debian-8.5.0-amd64-netinst.iso,xvdc:cdrom,r'
>    10.        ]
>    11.
>    12. boot = "c"
>
>
> On Thu, Aug 11, 2016 at 7:48 PM, Wei Liu <wei.liu2@citrix.com> 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@citrix.com>
>> 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
>>
>
>

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