[PATCH v3 1/6] arm64: rsi: Add RSI host call structure and helper function

[Will Deacon]

On Tue, Jul 21, 2026 at 01:11:43PM -0700, Kameron Carr wrote:
> Add struct rsi_host_call to rsi_smc.h, which represents the host call
> data structure used by the Realm Management Monitor (RMM) for the
> RSI_HOST_CALL interface. The structure contains a 16-bit immediate field
> and 31 general-purpose register values, aligned to 256 bytes as required
> by the CCA RMM specification.
> 
> Add rsi_host_call() static inline wrapper in rsi_cmds.h that invokes
> SMC_RSI_HOST_CALL with the physical address of the host call structure.
> This will be used by Hyper-V guest code to route hypercalls through the
> RSI interface when running inside an Arm CCA Realm.
> 
> Signed-off-by: Kameron Carr <kameroncarr at linux.microsoft.com>
> ---
>  arch/arm64/include/asm/rsi_cmds.h | 22 ++++++++++++++++++++++
>  arch/arm64/include/asm/rsi_smc.h  |  7 +++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
> index 2c8763876dfb7..9daf8008e5da2 100644
> --- a/arch/arm64/include/asm/rsi_cmds.h
> +++ b/arch/arm64/include/asm/rsi_cmds.h
> @@ -88,6 +88,28 @@ static inline long rsi_set_addr_range_state(phys_addr_t start,
>  	return res.a0;
>  }
>  
> +/**
> + * rsi_host_call - Make a Host call.
> + * @host_call_struct: IPA of host call structure
> + *
> + * This call will fail if the IPA of the host call structure:
> + * * is not aligned to 256 bytes,
> + * * is not protected / encrypted,
> + * * is RIPAS_EMPTY
> + *
> + * Returns:
> + *  On success, returns RSI_SUCCESS.
> + *  Otherwise, returns an error code.
> + */
> +static inline unsigned long rsi_host_call(phys_addr_t host_call_struct)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(SMC_RSI_HOST_CALL, host_call_struct, 0, 0, 0, 0, 0, 0,
> +		      &res);
> +	return res.a0;
> +}

As I've mentioned to Aneesh on two occasions already [1][2], this code
should be moved out of arch/arm64 before we add anything else to it.

Thanks,

Will

[1] https://lore.kernel.org/r/agsNO9cc7H-b0H8L@willie-the-truck
[2] https://lore.kernel.org/r/al_svOwkb5SleTWg@willie-the-truck