Re: [PATCH RFC 1/3] firmware: arm_firme: introduce arm_firme driver

[Kohei Enju <enju.kohei@fujitsu.com>]

On 10/22 14:17, Yeoreum Yun wrote:
> On Thu, Oct 22, 2026 at 06:48:49PM +0900, Kohei Enju wrote:
> > On 10/19 15:14, Yeoreum Yun wrote:
> > > The Realm Management Extension (FEAT_RME) is part of Arm Confidential
> > > Compute Architecture (CCA) and enables support for dynamic, attestable
> > > trusted execution environments ("Realms") on Arm systems.
> > > 
> > > Realm management flows depend on EL3 firmware for operations such as
> > > Realm construction, resource allocation and isolation, and attestation
> > > of initial Realm state.
> > > 
> > > The FIRME defines standard interfaces provided by EL3 firmware to
> > > satisfy these dependencies. These interfaces include:
> > > 
> > >   - Granule Protection Table management
> > >   - IDE key management for PCIe and CXL Root Ports
> > >   - Memory Encryption Context management
> > >   - Attestation token management
> > >   - Integrated device management
> > > 
> > > Each group of interfaces forms a FIRME service. A base FIRME service
> > > is also defined to provide common concepts, service discovery, and
> > > feature discovery across services.
> > > 
> > > FIRME interfaces are implemented at the EL3 boundary between the
> > > Non-secure, Realm, and Secure states. They may also be used on systems
> > > without FEAT_RME, for example to provide firmware-based attestation or
> > > security services.
> > > 
> > > arm_firme driver provides the common FIRME framework and service discovery
> > > support for client drivers using below FIRME services:
> > > 
> > >   - Base service.
> > >   - Attestation token management.
> > > 
> > > Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> > 
> > Does this series assume that the kernel is running in EL2 implicitly?
> > 
> > The FIRME spec says:
> >   An implementation of one or more FIRME services at a valid Exception level boundary between EL3 and the
> >   highest Exception level in a different Security state is called a FIRME instance.
> > 
> > and I think only NS-EL2 can call FIRME interfaces as a NS FIRME
> > instance, right?
> 
> Yeap. but it doens't forbid calling the FIRME from EL1 too.

I see. Then it's okay.

> As a just example, when the host running with pkvm, it could use
> where kernel running as EL1.

Thanks for the clarification, Yeoreum.

Thanks,
Kohei

> 
> [...]
> 
> -- 
> Sincerely,
> Yeoreum Yun