Re: [PATCH v3 4/7] kho: replace KHO FDT with kstate metadata

[Rob Herring <robh@kernel.org>]

On Tue, Sep 09, 2025 at 10:14:39PM +0200, Andrey Ryabinin wrote:
> Store KSTATE physical address & size instead of FDT in kho_data.
> and initialize KSTATE from kho_populate().
> To be able to use FDT in parallel with KSTATE place FDT
> address&size into 'struct kho_fdt' and save/restore it using KSTATE.
> 
> This finishes wiring KSTATE with KHO, making it fully functional.
> 
> Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
> ---
>  arch/x86/include/uapi/asm/setup_data.h |  4 +-
>  arch/x86/kernel/kexec-bzimage64.c      |  6 +--
>  arch/x86/kernel/setup.c                |  3 +-
>  drivers/of/fdt.c                       |  6 +--
>  include/linux/kexec.h                  |  2 +-
>  include/linux/kstate.h                 |  1 +
>  kernel/liveupdate/kexec_handover.c     | 60 +++++++++++++++++++++-----
>  7 files changed, 61 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/setup_data.h b/arch/x86/include/uapi/asm/setup_data.h
> index 2671c4e1b3a0..844f5b93473f 100644
> --- a/arch/x86/include/uapi/asm/setup_data.h
> +++ b/arch/x86/include/uapi/asm/setup_data.h
> @@ -83,8 +83,8 @@ struct ima_setup_data {
>   * Locations of kexec handover metadata
>   */
>  struct kho_data {
> -	__u64 fdt_addr;
> -	__u64 fdt_size;
> +	__u64 kstate_addr;
> +	__u64 kstate_size;
>  	__u64 scratch_addr;
>  	__u64 scratch_size;
>  } __attribute__((packed));

Isn't this part of the ABI which you can't just change.

Rob