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

[Sebastian Ene]

On Tue, Jun 16, 2026 at 02:00:39PM +0100, Vincent Donnefort wrote:
> 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@xxxxxxxxxx>
> > ---
> >  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? 
> 

Right, I think 17 including. Thanks for pointing out.

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

Sebastian