[libvirt] [PATCH 02/12] Introduce new domain create API virDomainCreateWithParams

[Marc Hartmayer]

On Wed, May 09, 2018 at 05:40 PM +0200, "Daniel P. Berrangé" <berrange at redhat.com> wrote:
> On Wed, May 09, 2018 at 04:56:12PM +0200, Marc Hartmayer wrote:
>> Introduce new libvirt API virDomainCreateWithParams that allows to
>> temporarily boot from another boot device, to use another kernel,
>> initrd, and cmdline than defined in the persistent domain
>> definition. All typed parameters are optional.
>>
>> The design of the API was chosen to ease future extensions.
>
> I don't really see the point in doing this. We already have the ability
> to temporary boot with a different configuration than is stored in
> the persistent XML. Just call virDomainCreateXML() passing in the
> alternative XML doc. This allows changing *any* aspect of the guest
> configuration, so we're not restricted to just bot device, kernel
> initrd and cmdline, and thus won't need to write more code anytime
> someone asks to be able to override something else too.

I know there is the API virDomainCreateXML for creating a transient
domain and that it’s possible to temporarily replace parts of the
persistent XML with it. But my idea is _not_ to add a functionality to
override parts of the persistent XML. My idea is to provide support
allowing an easy one-time switch of the boot device in a persistently
defined domain. For s390 it’s essential to have an easy way to change
the boot configuration since it “knows” only one boot device at a time
and it has no support for interactively changing the boot device during
the boot/IPL process.

I started out with a fixed API (as it was done for example with
virDomanCreateWithFiles) but than I liked the approach of providing an
more extensible and flexible API better. This is also the reason why I
used typed parameters for passing the arguments. This type of API is
also not restricted to boot order changes since it could be freely
expanded (e.g. passing file descriptors). I can certainly revert back to
the static API.

>
>
> Regards,
> Daniel
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--
Beste Grüße / Kind regards
   Marc Hartmayer

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