Re: [PATCH v2 0/7] KVM: arm64: Forward FFA_NOTIFICATION* calls to TrustZone

[Sebastian Ene <sebastianene@google.com>]

On Mon, Jun 15, 2026 at 10:47:45AM +0100, Will Deacon wrote:
> On Mon, Jun 15, 2026 at 07:43:55AM +0000, Sebastian Ene wrote:
> > On Sun, Jun 14, 2026 at 10:29:34AM +0100, Will Deacon wrote:
> > > Yes, that part now seems to be missing.
> > 
> > I am a bit worried to apply for all of them the check from the relayer
> > (ffa_check_unused_args_sbz) because of how it's written in the spec in
> > (11.2 Reserved parameter convention). To be more specific, there is no
> > mention of what the relayer is expected to do here (which is what hyp
> > does). It says 2 things:
> > 1. the caller (in this case the host driver) is expected to zero out
> > unused args
> > 2. the callee (Trustzone) ignores the values in these registers.
> > 
> > If we enforce SBZ in the relayer but (1) doesn't comply with it, we will
> > introduce a regression. I left it on purpose without enforcing
> > ffa_check_unused_args_sbz for the others.
> 
> I think that's ok -- if the caller isn't passing zeroes when it should,
> then it's already on borrowed (no pun intended!) time and it will need
> to be fixed.

Ok, thanks for the confirmation. Will include this and then spin a new
version of the patches.

> 
> Will

Thanks,
Sebastian