Re: [PATCH 0/5] hw/nvram/fw_cfg: Document and tighten up register layouts

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 03, 2026 at 10:41:32AM +0100, Peter Maydell wrote:
> These have all now been reviewed. Since fw_cfg is marked as
> Orphaned in MAINTAINERS,

I don't think fw cfg is good as orphaned.
Any takers? If not I guess I will have to add myself there.

> I'm going to take the series via
> target-arm.next. Let me know if anybody would prefer something else.
> 
> thanks
> -- PMM

Pls go ahead:
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>


> On Fri, 29 May 2026 at 18:46, Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> > We support the fw_cfg device on more architectures and machines that
> > we let on about in the documentation.  Luckily most of the new ones
> > (notably riscv and loongarch) have followed the straightforward layout
> > that the Arm virt board picked. Allowing every machine type to have
> > its own special-snowflake register layout has no particular benefits
> > and tends to result in guest OSes accumulating ifdef ladders to deal
> > with all the unnecessary variation.
> >
> > This patchset:
> >  * updates the docs to present the arm/riscv/loongarch memory
> >    mapped layout as the "standard" layout to be used by all
> >    new architectures/machines in future
> >  * adds the layouts used by various existing boards that we
> >    didn't document (PA-RISC, SPARC, PPC and MIPS)
> >  * tightens up fw_cfg_init_mem_dma() and fw_cfg_init_io_dma()
> >    functions so that they don't provide flexibility to the
> >    caller to pick their own weird new layout. None of the
> >    callers were using this flexibility, so it's better to
> >    have fw_cfg_init_mem_dma() give the "standard MMIO" layout
> >    and fw_cfg_init_io_dma() give the x86 ioport layout.
> >
> > thanks
> > -- PMM
> >
> > Peter Maydell (5):
> >   docs/specs/fw_cfg: Document all architecture register layouts
> >   hw/nvram/fw_cfg: Enforce standard layout for fw_cfg_init_mem_dma()
> >   hw/nvram/fw_cfg: Enforce standard layout for x86 fw_cfg I/O ports
> >   hw/nvram/fw_cfg: Remove support for I/O port fw_cfg without DMA
> >   hw/nvram/fw_cfg: Document fw_cfg_init_mem_nodma()
> >
> >  docs/specs/fw_cfg.rst     | 28 ++++++++++++++++---
> >  hw/arm/virt.c             |  2 +-
> >  hw/i386/fw_cfg.c          |  3 +-
> >  hw/i386/microvm.c         |  3 +-
> >  hw/i386/pc.c              |  3 +-
> >  hw/loongarch/fw_cfg.c     |  3 +-
> >  hw/nvram/fw_cfg.c         | 22 ++++++---------
> >  hw/riscv/virt.c           |  3 +-
> >  include/hw/nvram/fw_cfg.h | 58 +++++++++++++++++++++++++++++++++++----
> >  9 files changed, 92 insertions(+), 33 deletions(-)