[PATCH] KVM: arm64: Forward FFA_NOTIFICATION* calls to TrustZone

[Sudeep Holla]

On Fri, May 08, 2026 at 01:04:27PM +0000, Sebastian Ene wrote:
> On Thu, May 07, 2026 at 03:21:46PM +0100, Marc Zyngier wrote:
> > On Thu, 07 May 2026 15:13:06 +0100,
> > Sebastian Ene <sebastianene at google.com> wrote:
> > > 
> > > On Thu, May 07, 2026 at 02:36:46PM +0100, Marc Zyngier wrote:
> > > > On Thu, 07 May 2026 11:48:46 +0100,
> > > > Sebastian Ene <sebastianene at google.com> wrote:
> > > > > 
> > > > > On Wed, May 06, 2026 at 05:29:22PM +0100, Marc Zyngier wrote:
> > > > > 
> > > > > Hello Marc,
> > > > > 
> > > > > > [+ Sudeep]
> > > > > > 
> > > > > > On Fri, 01 May 2026 12:44:48 +0100,
> > > > > > Sebastian Ene <sebastianene at google.com> wrote:
> > > > > > > 
> > > > > > > Remove the FFA_NOTIFICATION* calls from the blocklist used by the pKVM
> > > > > > > FF-A proxy. This restriction was preventing the use of asynchronous
> > > > > > > signaling mechanisms defined by the Arm FF-A specification to
> > > > > > > communicate with the secure services.
> > > > > > > While these calls are markes as optional, there is no reason why the
> > > > > > > hypervisor proxy would block them because:
> > > > > > > 
> > > > > > > 1. Host is the Sole Non-Secure Endpoint: The Host operates as the
> > > > > > >    only Non-Secure VM ID (VM ID 0) recognized by the Secure World.
> > > > > > 
> > > > > > Where is this enforced?
> > > > > > 
> > > > > 
> > > > > There is no enforcement in place in the hypervisor since we don't proxy
> > > > > FF-A from guest VMs, there is only one non-secure user of this which is the host.
> > > > 
> > > > And again: what makes that VM ID 0? Why can't the host pick VM ID 32
> > > > and use that?
> > > > 
> > > 
> > > The host discovers its id through the FFA_ID_GET and TZ returns 0 in
> > 
> > Does it? How do you verify this?
> > 
>  
> It is written in the spec under 13.10 FFA_ID_GET ("ID value 0 must be
> returned at the Non-secure physical FF-A instance").

Sorry for chiming in late on this thread. Yes the spec states the above.
However, I am not sure how the host FF-A driver instance with pKVM FF-A
proxy needs to be categorised. I assume it plays a role of Non-secure physical
FF-A instance.

-- 
Regards,
Sudeep