Re: [PATCH v3 0/6] Add virtio-iommu built-in topology

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Fri, Sep 25, 2020 at 06:22:57AM -0400, Michael S. Tsirkin wrote:
> On Fri, Sep 25, 2020 at 10:48:06AM +0200, Jean-Philippe Brucker wrote:
> > On Fri, Aug 21, 2020 at 03:15:34PM +0200, Jean-Philippe Brucker wrote:
> > > Add a topology description to the virtio-iommu driver and enable x86
> > > platforms.
> > > 
> > > Since [v2] we have made some progress on adding ACPI support for
> > > virtio-iommu, which is the preferred boot method on x86. It will be a
> > > new vendor-agnostic table describing para-virtual topologies in a
> > > minimal format. However some platforms don't use either ACPI or DT for
> > > booting (for example microvm), and will need the alternative topology
> > > description method proposed here. In addition, since the process to get
> > > a new ACPI table will take a long time, this provides a boot method even
> > > to ACPI-based platforms, if only temporarily for testing and
> > > development.
> > > 
> > > v3:
> > > * Add patch 1 that moves virtio-iommu to a subfolder.
> > > * Split the rest:
> > >   * Patch 2 adds topology-helper.c, which will be shared with the ACPI
> > >     support.
> > >   * Patch 4 adds definitions.
> > >   * Patch 5 adds parser in topology.c.
> > > * Address other comments.
> > > 
> > > Linux and QEMU patches available at:
> > > https://jpbrucker.net/git/linux virtio-iommu/devel
> > > https://jpbrucker.net/git/qemu virtio-iommu/devel
> > 
> > I'm parking this work again, until we make progress on the ACPI table, or
> > until a platform without ACPI and DT needs it. Until then, I've pushed v4
> > to my virtio-iommu/topo branch and will keep it rebased on master.
> > 
> > Thanks,
> > Jean
> 
> I think you guys need to work on virtio spec too, not too much left to
> do there ...

I know it's ready and I'd really like to move on with this, but I'd rather
not commit it to the spec until we know it's going to be used at all. As
Gerd pointed out the one example we had, microvm, now supports ACPI. Since
we've kicked off the ACPI work anyway it isn't clear that the built-in
topology will be useful.

Thanks,
Jean