Re: [PATCH v3 1/7] KVM: arm64: Enforce strict SBZ checks in the FF-A proxy

[Vincent Donnefort <vdonnefort@google.com>]

On Tue, Jun 16, 2026 at 10:54:08AM +0000, Sebastian Ene wrote:
> Introduce a helper method ffa_check_unused_args_sbz to enforce strict
> arguments checking when the hypervisor acts as a relayer between the
> host and Trustzone.
> 
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 47 +++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 1af722771178..c723a21006aa 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++) {

Hum, should it be reg <= 17? 


> +		if (cpu_reg(ctxt, reg))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +

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