Re: [PATCH v2 4/8] xen/arm: vsmc: Enable handling SiP-owned SCMI SMC calls

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 30 Sep 2024, Andrei Cherechesu (OSS) wrote:
> From: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>
> 
> Change the handling of SiP SMC calls to be more generic,
> instead of directly relying on the `platform_smc()` callback
> implementation.
> 
> Try to handle the SiP SMC first through the `platform_smc()`
> callback (if implemented). If not handled, check if the
> SCMI layer is available and that the SMC is a valid SCMI
> message. Handle it then within the SCMI layer which forwards
> it to EL3 FW, only if the SMC comes from Dom0.
> 
> Signed-off-by: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/arch/arm/vsmc.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
> index 7f2f5eb9ce..0de194a132 100644
> --- a/xen/arch/arm/vsmc.c
> +++ b/xen/arch/arm/vsmc.c
> @@ -14,6 +14,7 @@
>  #include <asm/cpufeature.h>
>  #include <asm/monitor.h>
>  #include <asm/regs.h>
> +#include <asm/scmi-smc.h>
>  #include <asm/smccc.h>
>  #include <asm/tee/ffa.h>
>  #include <asm/tee/tee.h>
> @@ -224,6 +225,22 @@ static bool handle_sssc(struct cpu_user_regs *regs)
>      }
>  }
>  
> +/* Secure Calls defined by the Silicon Provider (SiP) */
> +static bool handle_sip(struct cpu_user_regs *regs)
> +{
> +    uint32_t fid = (uint32_t)get_user_reg(regs, 0);
> +
> +    /* Firstly, let each platform define custom handling for these SMCs */
> +    if ( platform_smc(regs) )
> +        return true;
> +
> +    /* Otherwise, if valid SCMI SMC, forward the call to EL3 */
> +    if ( scmi_is_enabled() && scmi_is_valid_smc_id(fid) )
> +        return scmi_handle_smc(regs);
> +
> +    return false;
> +}
> +
>  /*
>   * vsmccc_handle_call() - handle SMC/HVC call according to ARM SMCCC.
>   * returns true if that was valid SMCCC call (even if function number
> @@ -288,7 +305,7 @@ static bool vsmccc_handle_call(struct cpu_user_regs *regs)
>              handled = handle_sssc(regs);
>              break;
>          case ARM_SMCCC_OWNER_SIP:
> -            handled = platform_smc(regs);
> +            handled = handle_sip(regs);
>              break;
>          case ARM_SMCCC_OWNER_TRUSTED_APP ... ARM_SMCCC_OWNER_TRUSTED_APP_END:
>          case ARM_SMCCC_OWNER_TRUSTED_OS ... ARM_SMCCC_OWNER_TRUSTED_OS_END:
> -- 
> 2.45.2
>