Re: [Xen-devel] RFC: QEMU bumping memory limit and domain restore

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jun 02, 2015 at 04:49:09PM +0100, Ian Campbell wrote:
> On Tue, 2015-06-02 at 15:08 +0100, Wei Liu wrote:
> [...]
> > > So here is a proof of concept patch to record and honour that value
> > > during migration.  A new field is added in IDL. Note that we don't
> > > provide xl level config option for it and mandate it to be default value
> > > during domain creation. This is to prevent libxl user from using it to
> > > avoid unforeseen repercussions.
> > [...]
> > > This field is mandated to be default value during guest creation to
> > > avoid unforeseen repercussions. It's only honour when restoring a guest.
> 
> IMHO this means that the libxl API/IDL is the wrong place for this
> value. Only user and/or application serviceable parts belong in the API.
> 

I feared the same when I wrote the patch.

> So while I agree that this value need to be communicated across a
> migration, the JSON blob is not the right mechanism for doing so. IOW if
> you go down this general path I think you need a new
> field/record/whatever in the migration protocol at some layer or other
> (if not libxc then at the libxl layer).
> 

There isn't a libxl layer for migration at the moment. The stream is xl
+ libxc. Maybe we should wait till migration v2 is in place.

> To my mind this "actual state" vs "user configured state" is more akin
> to the sorts of things which is in the hypervisor save blob or something
> like that (nb: This is not a suggestion that it should go there).
> 
> IIRC Don also outlined another case, which is
>     xl create -p
>     xl migrate
>     xl unpause
> 
> Which might need more thought if any bumping can happen after the
> migrate i.e. on unpause?
> 

I just tried. It failed at "xl migrate".

Wei.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel