Re: Save/Restore is not working properly

[Cendrin Sa <cendrinoe@gmail.com>]

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Hi again,
So save/restore has a bug or not? I still have problem with it when i use
LVM.

On Sat, Aug 13, 2016 at 11:10 AM, Cendrin Sa <cendrinoe@gmail.com> wrote:

> 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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