Re: [PATCH v2 1/2] docs: update hyperlaunch device tree

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 3 Aug 2023, Daniel P. Smith wrote:
> > Also, what is the plan for the existing dom0less dt properties?
> > Will they need to be moved to new /hypervisor node or we will have to parse
> > both /chosen and /hypervisor nodes?
> 
> In the proposal I sent to xen-devel in response to Luca's RFC for rebranding
> dom0less features under hyperlaunch, that is the purpose of this commit. Get
> this document up to date with what was done in v1 along with what we are
> planning/working on for hyperlaunch. One could think of this as effectively
> the API to the capabilities hyperlaunch will provide. Not just how to
> construct a domain, but what kinds of domains can be constructed by
> hyperlaunch. Step one of the proposal is to publish a patch upon which we all
> can iterate over and get to an agreement on a suitable interface for all. The
> next step would be the introduction of hyperlaunch dom0less compatibility
> mode, that would see the moving of the parsing logic for the existing dom0less
> nodes under /xen/common/domain-builder. It would continue to exist there even
> after hyperlaunch proper is merged and can remain there for backward
> compatibility until there is a decision to retire the compatibility interface.

I like this plan. The two interfaces are so similar that it is basically
one interface with a couple of tiny differences.

So I expect we would move the existing dom0less parsing code to common/,
add a couple of extensions (such as parsing /hypervisor in addition to
/chosen) and use it as it.

Later on, after a few years of using /hypervisor instead of /chosen, if
nobody is using /chosen anymore, we could retire /chosen completely. But
this is just one DT node/property that gets retired (there are a couple
of others). I don't imagine we'll have a full new implementation of the
DT parsing logic that supersedes the existing implementation of it
(especially considering the difficulty of maintaining 2 different parsing
logics in the hypervisor for similar interfaces).

Same thing for the DT interface documentation. I don't think we need two
DT interface docs? We could start with the existing dom0less interface
(docs/misc/arm/device-tree/booting.txt), and move it somewhere common
like docs/misc/device-tree.

Then add any changes or extensions required by other architecture, such
as x86 and RISC-V.

For sure for x86 we need "module-index". I don't know if anything else
is must-have to get it to work on x86 but if there is, we should add
those too.