Re: [Xen-devel] [PATCH v2 00/20] VM forking

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Tue, Dec 31, 2019 at 8:11 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
>
> On Tue, Dec 31, 2019 at 08:00:17AM -0700, Tamas K Lengyel wrote:
> > On Tue, Dec 31, 2019 at 3:40 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> 
> > wrote:
> > >
> > > On Mon, Dec 30, 2019 at 05:37:38PM -0700, Tamas K Lengyel wrote:
> > > > On Mon, Dec 30, 2019 at 5:20 PM Julien Grall <julien.grall@xxxxxxxxx> 
> > > > wrote:
> > > > >
> > > > > Hi,
> > > > >
> > > > > On Mon, 30 Dec 2019, 20:49 Tamas K Lengyel, <tamas@xxxxxxxxxxxxx> 
> > > > > wrote:
> > > > >>
> > > > >> On Mon, Dec 30, 2019 at 11:43 AM Julien Grall <julien@xxxxxxx> wrote:
> > > > >> But keep in mind that the "fork-vm" command even with this update
> > > > >> would still not produce for you a "fully functional" VM on its own.
> > > > >> The user still has to produce a new VM config file, create the new
> > > > >> disk, save the QEMU state, etc.
> > >
> > > IMO the default behavior of the fork command should be to leave the
> > > original VM paused, so that you can continue using the same disk and
> > > network config in the fork and you won't need to pass a new config
> > > file.
> > >
> > > As Julien already said, maybe I wasn't clear in my previous replies:
> > > I'm not asking you to implement all this, it's fine if the
> > > implementation of the fork-vm xl command requires you to pass certain
> > > options, and that the default behavior is not implemented.
> > >
> > > We need an interface that's sane, and that's designed to be easy and
> > > comprehensive to use, not an interface built around what's currently
> > > implemented.
> >
> > OK, so I think that would look like "xl fork-vm <parent_domid>" with
> > additional options for things like name, disk, vlan, or a completely
> > new config, all of which are currently not implemented, + an
> > additional option to not launch QEMU at all, which would be the only
> > one currently working. Also keeping the separate "xl fork-launch-dm"
> > as is. Is that what we are talking about?
>
> I think fork-launch-vm should just be an option of fork-vm (ie:
> --launch-dm-only or some such). I don't think there's a reason to have
> a separate top-level command to just launch the device model.

It's just that the fork-launch-dm needs the domid of the fork, while
the fork-vm needs the parent's domid. But I guess we can interpret the
"domid" required input differently depending on which sub-option is
specified for the command. Let's see how it pans out.

Thanks,
Tamas

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