Re: [PATCH v1 0/4] virt: vmgenid: Add devicetree bindings support

Rob Herring
2024-03-21T13:32:53Z

On Wed, Mar 20, 2024 at 04:55:45PM +0000, David Woodhouse wrote:
> On Wed, 2024-03-20 at 11:15 -0500, Rob Herring wrote:
> > On Wed, Mar 20, 2024 at 01:50:43PM +0000, David Woodhouse wrote:
> > > On Tue, 2024-03-19 at 16:24 +0100, Krzysztof Kozlowski wrote:
> > > > On 19/03/2024 15:32, Sudan Landge wrote:
> > > > > This small series of patches aims to add devicetree bindings support for
> > > > > the Virtual Machine Generation ID (vmgenid) driver.
> > > > >
> > > > > Virtual Machine Generation ID driver was introduced in commit af6b54e2b5ba
> > > > > ("virt: vmgenid: notify RNG of VM fork and supply generation ID") as an
> > > > > ACPI only device.
> > > > > We would like to extend vmgenid to support devicetree bindings because:
> > > > > 1. A device should not be defined as an ACPI or DT only device.
> >
> > This (and the binding patch) tells me nothing about what "Virtual
> > Machine Generation ID driver" is and isn't really justification for
> > "why".
>
> It's a reference to a memory area which the OS can use to tell whether
> it's been snapshotted and restored (or 'forked'). A future submission
> should have a reference to something like
> https://www.qemu.org/docs/master/specs/vmgenid.html or the Microsoft
> doc which is linked from there.

That doc mentions fw_cfg for which we already have a binding. Why can't
it be used/extended here?

Rob

[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/firmware/qemu%2Cfw-cfg-mmio.yaml