On Tue, Aug 19, 2025 at 11:22:45PM +0000, Evangelos Petrongonas wrote:
> During early initialisation, after a kexec, other components, like EFI
> need to know if a KHO enabled kexec is performed. The `kho_is_enabled`
> function is not enough as in the early stages, it only reflects
> whether the cmdline has KHO enabled, not if an actual KHO FDT exists.
>
> Extend the KHO API with `is_kho_boot()` to provide a way for components
> to check if a KHO enabled kexec is performed.
>
> Signed-off-by: Evangelos Petrongonas <epet...@amazon.de>
> ---
> include/linux/kexec_handover.h | 6 ++++++
> kernel/kexec_handover.c | 20 ++++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> index 348844cffb13..559d13a3bc44 100644
> --- a/include/linux/kexec_handover.h
> +++ b/include/linux/kexec_handover.h
> @@ -40,6 +40,7 @@ struct kho_serialization;
>
> #ifdef CONFIG_KEXEC_HANDOVER
> bool kho_is_enabled(void);
> +bool is_kho_boot(void);
>
> int kho_preserve_folio(struct folio *folio);
> int kho_preserve_phys(phys_addr_t phys, size_t size);
> @@ -60,6 +61,11 @@ static inline bool kho_is_enabled(void)
> return false;
> }
>
> +static inline bool is_kho_boot(void)
> +{
> + return false;
> +}
> +
> static inline int kho_preserve_folio(struct folio *folio)
> {
> return -EOPNOTSUPP;
> diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
> index 69b953551677..a1a4e76e0ff1 100644
> --- a/kernel/kexec_handover.c
> +++ b/kernel/kexec_handover.c
> @@ -925,6 +925,26 @@ static const void *kho_get_fdt(void)
> return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
> }
>
> +/**
> + * is_kho_boot - check if current kernel was booted via KHO-enabled
> + * kexec
> + *
> + * This function checks if the current kernel was loaded through a kexec
> + * operation with KHO enabled, by verifying both that KHO is enabled via
> + * cmdline AND that a valid KHO FDT was passed.
> + *
> + * Note: This function returns reliable results only after
> + * kho_populate() has been called during early boot. Before that,
> + * it may return false even if KHO data is present.
> + *
> + * Return: true if booted via KHO-enabled kexec, false otherwise
> + */
> +bool is_kho_boot(void)
> +{
> + return !!kho_get_fdt() && kho_enable;
Let's drop '&& kho_enable' and presume that a kernel that booted with KHO
FDT goes through KHO revival.
With that change feel free to add
Reviewed-by: Mike Rapoport (Microsoft) <r...@kernel.org>
> +}
> +EXPORT_SYMBOL_GPL(is_kho_boot);
> +
> /**
> * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
> * @name: the name of the sub FDT passed to kho_add_subtree().
> --
> 2.47.3
--
Sincerely yours,
Mike.
