Re: [XEN][PATCH v9 05/19] xen/arm: Add CONFIG_OVERLAY_DTB

[Julien Grall <julien@xxxxxxx>]

On 25/08/2023 04:17, Vikram Garhwal wrote:
> Hi Julien,
> On Tue, Aug 22, 2023 at 08:10:05PM +0100, Julien Grall wrote:
> > Hi Vikram,
> >
> > On 19/08/2023 01:28, Vikram Garhwal wrote:
> > > Introduce a config option where the user can enable support for adding/removing
> > > device tree nodes using a device tree binary overlay.
> > >
> > > Update SUPPORT.md and CHANGELOG.md to state the Device Tree Overlays support for
> > > Arm.
> > >
> > > Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> > > Acked-by: Henry Wang <Henry.Wang@xxxxxxx>
> > > Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
> > >
> > > ---
> > > Changes from v7:
> > >       Add this feature as "experimental support" in CHANGELOG.md
> > > ---
> > > ---
> > >    CHANGELOG.md         | 3 ++-
> > >    SUPPORT.md           | 6 ++++++
> > >    xen/arch/arm/Kconfig | 5 +++++
> > >    3 files changed, 13 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/CHANGELOG.md b/CHANGELOG.md
> > > index 7d7e0590f8..47098dbfca 100644
> > > --- a/CHANGELOG.md
> > > +++ b/CHANGELOG.md
> > > @@ -24,7 +24,8 @@ The format is based on [Keep a 
> > > Changelog](https://keepachangelog.com/en/1.0.0/)
> > >     - xl/libxl can customize SMBIOS strings for HVM guests.
> > >     - Add support for AVX512-FP16 on x86.
> > >     - On Arm, Xen supports guests running SVE/SVE2 instructions. (Tech Preview)
> > > -
> > > + - On Arm, experimental support for dynamic addition/removal of Xen device tree
> > > +   nodes using a device tree overlay binary(.dtbo).
> > Typo: missing space before (.
> >
> > >    ## 
> > > [4.17.0](https://xenbits.xen.org/gitweb/?p=xen.git;a=shortlog;h=RELEASE-4.17.0) 
> > > - 2022-12-12
> > > diff --git a/SUPPORT.md b/SUPPORT.md
> > > index 35a6249e03..8eb006565c 100644
> > > --- a/SUPPORT.md
> > > +++ b/SUPPORT.md
> > > @@ -844,6 +844,12 @@ No support for QEMU backends in a 16K or 64K domain.
> > >        Status: Supported
> > > +### Device Tree Overlays
> > > +
> > > +Add/Remove device tree nodes using a device tree overlay binary(.dtbo).
> > Same here. I don't suggest to handle it on commit because this is not
> > something I want to merge without the rest of the series.
> >
> > > +
> > > +    Status, ARM: Experimental
> > > +
> > >    ### ARM: Guest ACPI support
> > >        Status: Supported
> > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > > index fd57a82dd2..02c4796438 100644
> > > --- a/xen/arch/arm/Kconfig
> > > +++ b/xen/arch/arm/Kconfig
> > > @@ -92,6 +92,11 @@ config HAS_ITS
> > >            bool "GICv3 ITS MSI controller support (UNSUPPORTED)" if UNSUPPORTED
> > >            depends on GICV3 && !NEW_VGIC && !ARM_32
> > > +config OVERLAY_DTB
> > > +       bool "DTB overlay support (UNSUPPORTED)" if UNSUPPORTED
> > > +       help
> > > +         Dynamic addition/removal of Xen device tree nodes using a dtbo.
> > Do we have any documentation in the tree of the limitations and how this
> > works?
> >
> > The reason I am asking is the wording here suggests that it would be
> > possible to remove nodes from the original Device-Tree. AFAIU this is not
> > possible with the implementation and you are not planning to handle it.
> > Correct?
> Yes, that is correct. This series doesn't remove the nodes which are not added
> by overlay before.
>
> I will add a document file. Is this needs to be in .pandoc or .txt format?
I think we now prefer .pandoc.

Cheers,

--
Julien Grall