Re: [PATCH v2 1/7] KVM: arm64: Support FFA_NOTIFICATION_BITMAP_CREATE in host handler

[Vincent Donnefort <vdonnefort@google.com>]

Hi Seb,

On Mon, Jun 08, 2026 at 04:55:43PM +0000, Sebastian Ene wrote:
> Allow FF-A notification bitmap creation messages to be forwarded to
> Trustzone from the host and introduce a helper to check for SBZ
> register fields.
> 
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 36 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 1af722771178..c20d45191085 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -71,6 +71,18 @@ static u32 hyp_ffa_version;
>  static bool has_version_negotiated;
>  static hyp_spinlock_t version_lock;
>  
> +static bool ffa_check_unused_args_sbz(struct kvm_cpu_context *ctxt, int first_reg)
> +{
> +	int reg;
> +
> +	for (reg = first_reg; reg < 17; reg++) {

The upper limit should probably be something like ARRAY_SIZE(ctx->regs.regs) - first_reg?

> +		if (cpu_reg(ctxt, reg))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  static void ffa_to_smccc_error(struct arm_smccc_1_2_regs *res, u64 ffa_errno)
>  {
>  	*res = (struct arm_smccc_1_2_regs) {
> @@ -676,7 +688,6 @@ static bool ffa_call_supported(u64 func_id)
>  	case FFA_MEM_DONATE:
>  	case FFA_MEM_RETRIEVE_REQ:
>         /* Optional notification interfaces added in FF-A 1.1 */
> -	case FFA_NOTIFICATION_BITMAP_CREATE:
>  	case FFA_NOTIFICATION_BITMAP_DESTROY:
>  	case FFA_NOTIFICATION_BIND:
>  	case FFA_NOTIFICATION_UNBIND:
> @@ -862,6 +873,26 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>  	hyp_spin_unlock(&host_buffers.lock);
>  }
>  
> +static void do_ffa_notif_bitmap_create(struct arm_smccc_1_2_regs *res,
> +				       struct kvm_cpu_context *ctxt)
> +{
> +	DECLARE_REG(u32, vmid, ctxt, 1);
> +	struct arm_smccc_1_2_regs *args;
> +
> +	if (ffa_check_unused_args_sbz(ctxt, 3)) {

Is that expected we start at 3 but only read 0 and 1?

> +		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}
> +
> +	if (vmid != HOST_FFA_ID) {
> +		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}
> +
> +	args = (void *)&ctxt->regs.regs[0];
> +	arm_smccc_1_2_smc(args, res);

Should be hyp_smccc_1_2_smc()

> +}
> +
>  bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  {
>  	struct arm_smccc_1_2_regs res;
> @@ -920,6 +951,9 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  	case FFA_PARTITION_INFO_GET:
>  		do_ffa_part_get(&res, host_ctxt);
>  		goto out_handled;
> +	case FFA_NOTIFICATION_BITMAP_CREATE:
> +		do_ffa_notif_bitmap_create(&res, host_ctxt);
> +		goto out_handled;
>  	}
>  
>  	if (ffa_call_supported(func_id))
> -- 
> 2.54.0.1064.gd145956f57-goog
>