reboot dom0 without vps downtime

reboot dom0 without vps downtime

[Vasiliy Tolstov]

Hi. I'm not using xen for past 4 years (switched to kvm) but now i'm
interesting - does it possible to reboot (for update) dom0 ?
As i know, xen stubdoms can dedicate network, disk and xenstored to
external domains. Does it possible to reboot dom0 ?


-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

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Re: reboot dom0 without vps downtime

[Juergen Gross]

On 17/03/17 08:09, Vasiliy Tolstov wrote:
> Hi. I'm not using xen for past 4 years (switched to kvm) but now i'm
> interesting - does it possible to reboot (for update) dom0 ?
> As i know, xen stubdoms can dedicate network, disk and xenstored to
> external domains. Does it possible to reboot dom0 ?

Not yet.


Juergen


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Re: reboot dom0 without vps downtime

[Vasiliy Tolstov]

2017-03-17 11:21 GMT+03:00 Juergen Gross <jgross@suse.com>:
> Not yet.


Does this planned or how can i do that if i can write some code ? =)

-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

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Re: reboot dom0 without vps downtime

[Juergen Gross]

On 17/03/17 09:23, Vasiliy Tolstov wrote:
> 2017-03-17 11:21 GMT+03:00 Juergen Gross <jgross@suse.com>:
>> Not yet.
> 
> 
> Does this planned or how can i do that if i can write some code ? =)

(Dropping xen-users)

I have plans for the future, but I'm not sure when I'll have enough
time for it.

Any help on this topic is welcome, of course!

I think (at least) the following features are missing:

- capability to specify a (new) dom0 kernel and initrd for reboot of
  dom0: both must be transferred to the hypervisor in a memory buffer
  which will be used for the reboot
- dom0 reboot capability in hypervisor using the kernel and initrd
  from the memory buffer, without destroying other domains
- dom0 has to check for presence of xenstore-stubdom before trying to
  create it. In case xenstore is already existing connect to it and
  re-establish needed connections to other domains, don't auto-start
  any other domains in this case

I'm sure there are lots of other little pieces missing, but those can
be addressed after above main features are available.


Juergen

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Re: reboot dom0 without vps downtime

[Vasiliy Tolstov]

2017-03-17 11:47 GMT+03:00 Juergen Gross <jgross@suse.com>:
> (Dropping xen-users)
>
> I have plans for the future, but I'm not sure when I'll have enough
> time for it.
>
> Any help on this topic is welcome, of course!
>
> I think (at least) the following features are missing:
>
> - capability to specify a (new) dom0 kernel and initrd for reboot of
>   dom0: both must be transferred to the hypervisor in a memory buffer
>   which will be used for the reboot
> - dom0 reboot capability in hypervisor using the kernel and initrd
>   from the memory buffer, without destroying other domains
> - dom0 has to check for presence of xenstore-stubdom before trying to
>   create it. In case xenstore is already existing connect to it and
>   re-establish needed connections to other domains, don't auto-start
>   any other domains in this case
>
> I'm sure there are lots of other little pieces missing, but those can
> be addressed after above main features are available.


What about qemu processes (i'm interesting on hvm domains pvh or how
they naming now)

-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

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Re: reboot dom0 without vps downtime

[Juergen Gross]

On 17/03/17 09:49, Vasiliy Tolstov wrote:
> 2017-03-17 11:47 GMT+03:00 Juergen Gross <jgross@suse.com>:
>> (Dropping xen-users)
>>
>> I have plans for the future, but I'm not sure when I'll have enough
>> time for it.
>>
>> Any help on this topic is welcome, of course!
>>
>> I think (at least) the following features are missing:
>>
>> - capability to specify a (new) dom0 kernel and initrd for reboot of
>>   dom0: both must be transferred to the hypervisor in a memory buffer
>>   which will be used for the reboot
>> - dom0 reboot capability in hypervisor using the kernel and initrd
>>   from the memory buffer, without destroying other domains
>> - dom0 has to check for presence of xenstore-stubdom before trying to
>>   create it. In case xenstore is already existing connect to it and
>>   re-establish needed connections to other domains, don't auto-start
>>   any other domains in this case
>>
>> I'm sure there are lots of other little pieces missing, but those can
>> be addressed after above main features are available.
> 
> 
> What about qemu processes (i'm interesting on hvm domains pvh or how
> they naming now)

For pvh domains qemu processes aren't mandatory. All mandatory backends
like disk and net must live in stubdoms for dom0 being rebootable, of
course.

For hvm domains you have to use qemu-stubdoms. Those are supported with
qemu-traditional only right now. Support of upstream qemu in a stubdom
is another feature which would be nice to have, but this is no blocking
point for dom0 reboot.


Juergen


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Re: reboot dom0 without vps downtime

[Wei Liu]

On Fri, Mar 17, 2017 at 09:56:44AM +0100, Juergen Gross wrote:
> On 17/03/17 09:49, Vasiliy Tolstov wrote:
> > 2017-03-17 11:47 GMT+03:00 Juergen Gross <jgross@suse.com>:
> >> (Dropping xen-users)
> >>
> >> I have plans for the future, but I'm not sure when I'll have enough
> >> time for it.
> >>
> >> Any help on this topic is welcome, of course!
> >>
> >> I think (at least) the following features are missing:
> >>
> >> - capability to specify a (new) dom0 kernel and initrd for reboot of
> >>   dom0: both must be transferred to the hypervisor in a memory buffer
> >>   which will be used for the reboot
> >> - dom0 reboot capability in hypervisor using the kernel and initrd
> >>   from the memory buffer, without destroying other domains
> >> - dom0 has to check for presence of xenstore-stubdom before trying to
> >>   create it. In case xenstore is already existing connect to it and
> >>   re-establish needed connections to other domains, don't auto-start
> >>   any other domains in this case
> >>
> >> I'm sure there are lots of other little pieces missing, but those can
> >> be addressed after above main features are available.
> > 
> > 
> > What about qemu processes (i'm interesting on hvm domains pvh or how
> > they naming now)
> 
> For pvh domains qemu processes aren't mandatory. All mandatory backends
> like disk and net must live in stubdoms for dom0 being rebootable, of
> course.
> 

stubdoms -> backend domains to be precise.  I think you can use any
normal OS for that purpose.

(I realise people might be using stubdom with slightly different
meanings, but to me it mostly means unikernel-like domains, because
that's how it is done at the moment in Xen. The definition of stubdom is
up for debate, of course).

Wei.

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