[PATCH v5 2/4] firmware: arm_sdei: add SDEI_EVENT_SIGNAL support

[Usama Arif]

On Mon, 29 Jun 2026 16:07:16 +0100 Kiryl Shutsemau <kirill at shutemov.name> wrote:

> From: "Kiryl Shutsemau (Meta)" <kas at kernel.org>
> 
> Add sdei_event_signal(), a thin wrapper over the SDEI_EVENT_SIGNAL call
> (DEN0054) that makes the software-signalled event (event 0) pending on a
> target PE -- delivered NMI-like even when that PE has interrupts masked.
> It takes no locks, so it is safe to call from NMI / crash context.
> 
> Signed-off-by: Kiryl Shutsemau (Meta) <kas at kernel.org>
> Reviewed-by: Douglas Anderson <dianders at chromium.org>
> ---
>  drivers/firmware/arm_sdei.c   | 12 ++++++++++++
>  include/linux/arm_sdei.h      |  6 ++++++
>  include/uapi/linux/arm_sdei.h |  1 +
>  3 files changed, 19 insertions(+)
> 
> diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
> index c161cf263547..e8dd2f0f3919 100644
> --- a/drivers/firmware/arm_sdei.c
> +++ b/drivers/firmware/arm_sdei.c
> @@ -339,6 +339,18 @@ static void _ipi_unmask_cpu(void *ignored)
>  	sdei_unmask_local_cpu();
>  }
>  
> +/*
> + * Signal the software-signalled event (event 0) to @mpidr. Does nothing
> + * but the SMC -- no locks, no event lookup -- so it is safe from NMI /
> + * crash context (e.g. the cross-CPU NMI service).
> + */
> +int sdei_event_signal(u32 event_num, u64 mpidr)
> +{
> +	return invoke_sdei_fn(SDEI_1_0_FN_SDEI_EVENT_SIGNAL, event_num,
> +			      mpidr, 0, 0, 0, NULL);
> +}
> +NOKPROBE_SYMBOL(sdei_event_signal);
> +

Same as patch 1, can this be merged in patch 3? Its good to keep functions
where they are used.

>  /*
>   * Was SDEI firmware probed and is it usable?  Lets optional consumers skip
>   * registering an event -- and the warning a failed registration emits -- on
> diff --git a/include/linux/arm_sdei.h b/include/linux/arm_sdei.h
> index b07113eeeff7..b9dc21c241be 100644
> --- a/include/linux/arm_sdei.h
> +++ b/include/linux/arm_sdei.h
> @@ -37,6 +37,12 @@ int sdei_event_unregister(u32 event_num);
>  int sdei_event_enable(u32 event_num);
>  int sdei_event_disable(u32 event_num);
>  
> +/*
> + * Signal the software-signalled event (event 0) to another PE, NMI-like.
> + * @mpidr is the target's MPIDR affinity.
> + */
> +int sdei_event_signal(u32 event_num, u64 mpidr);
> +
>  /* Was SDEI firmware probed and usable? */
>  bool sdei_is_present(void);
>  
> diff --git a/include/uapi/linux/arm_sdei.h b/include/uapi/linux/arm_sdei.h
> index af0630ba5437..22eb61612673 100644
> --- a/include/uapi/linux/arm_sdei.h
> +++ b/include/uapi/linux/arm_sdei.h
> @@ -22,6 +22,7 @@
>  #define SDEI_1_0_FN_SDEI_PE_UNMASK			SDEI_1_0_FN(0x0C)
>  #define SDEI_1_0_FN_SDEI_INTERRUPT_BIND			SDEI_1_0_FN(0x0D)
>  #define SDEI_1_0_FN_SDEI_INTERRUPT_RELEASE		SDEI_1_0_FN(0x0E)
> +#define SDEI_1_0_FN_SDEI_EVENT_SIGNAL			SDEI_1_0_FN(0x0F)
>  #define SDEI_1_0_FN_SDEI_PRIVATE_RESET			SDEI_1_0_FN(0x11)
>  #define SDEI_1_0_FN_SDEI_SHARED_RESET			SDEI_1_0_FN(0x12)
>  
> -- 
> 2.54.0
> 
>