Re: [RFC] Support for Arm CCA VMs on Linux

[Jonathan Cameron]

On Fri, 14 Jul 2023 16:03:37 +0100
Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:

> Hi Jonathan
> 
> On 14/07/2023 14:46, Jonathan Cameron wrote:
> > On Fri, 27 Jan 2023 11:22:48 +0000
> > Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > 
> > 
> > Hi Suzuki,
> > 
> > Looking at this has been on the backlog for a while from our side and we are finally
> > getting to it.  So before we dive in and given it's been 6 months, I wanted to check
> > if you expect to post a new version shortly or if there is a rebased tree available?  
> 
> Thanks for your interest. We have been updating our trees to the latest
> RMM specification (v1.0-eac2 now) and also rebasing Linux/KVM on top of
> v6.5-rc1. We will post this as soon as we have all the components ready
> (and the TF-RMM). At the earliest, this would be around early September.
> 
> That said, the revised version will have the following changes :
>   - Changes to the Stage2 management
>   - Changes to RMM memory management for Realm
>   - PMU/SVE support
> 
> Otherwise, most of the changes remain the same (e.g., UABI). Happy to
> hear feedback on those areas.

Hi Suzuki,

Thanks for the update.  If there is any chance of visibility of changes
via a git tree etc that would be great in the meantime.  If not, such is life
and I'll try to wait patiently :) + we'll review the existing code.

Jonathan

> 
> 
> Kind regards
> Suzuki
> 
> > 
> > Jonathan
> >      
> >> We are happy to announce the early RFC version of the Arm
> >> Confidential Compute Architecture (CCA) support for the Linux
> >> stack. The intention is to seek early feedback in the following areas:
> >>   * KVM integration of the Arm CCA
> >>   * KVM UABI for managing the Realms, seeking to generalise the operations
> >>     wherever possible with other Confidential Compute solutions.
> >>     Note: This version doesn't support Guest Private memory, which will be added
> >>     later (see below).
> >>   * Linux Guest support for Realms
> >>
> >> Arm CCA Introduction
> >> =====================
> >>
> >> The Arm CCA is a reference software architecture and implementation that builds
> >> on the Realm Management Extension (RME), enabling the execution of Virtual
> >> machines, while preventing access by more privileged software, such as hypervisor.
> >> The Arm CCA allows the hypervisor to control the VM, but removes the right for
> >> access to the code, register state or data that is used by VM.
> >> More information on the architecture is available here[0].
> >>
> >>      Arm CCA Reference Software Architecture
> >>
> >>          Realm World    ||    Normal World   ||  Secure World  ||
> >>                         ||        |          ||                ||
> >>   EL0 x-------x         || x----x | x------x ||                ||
> >>       | Realm |         || |    | | |      | ||                ||
> >>       |       |         || | VM | | |      | ||                ||
> >>   ----|  VM*  |---------||-|    |---|      |-||----------------||
> >>       |       |         || |    | | |  H   | ||                ||
> >>   EL1 x-------x         || x----x | |      | ||                ||
> >>           ^             ||        | |  o   | ||                ||
> >>           |             ||        | |      | ||                ||
> >>   ------- R*------------------------|  s  -|---------------------
> >>           S             ||          |      | ||                ||
> >>           I             ||          |  t   | ||                ||
> >>           |             ||          |      | ||                ||
> >>           v             ||          x------x ||                ||
> >>   EL2    RMM*           ||              ^    ||                ||
> >>           ^             ||              |    ||                ||
> >>   ========|=============================|========================
> >>           |                             | SMC
> >>           x--------- *RMI* -------------x
> >>
> >>   EL3                   Root World
> >>                         EL3 Firmware
> >>   ===============================================================
> >> Where :
> >>   RMM - Realm Management Monitor
> >>   RMI - Realm Management Interface
> >>   RSI - Realm Service Interface
> >>   SMC - Secure Monitor Call
> >>
> >> RME introduces a new security state "Realm world", in addition to the
> >> traditional Secure and Non-Secure states. The Arm CCA defines a new component,
> >> Realm Management Monitor (RMM) that runs at R-EL2. This is a standard piece of
> >> firmware, verified, installed and loaded by the EL3 firmware (e.g, TF-A), at
> >> system boot.
> >>
> >> The RMM provides standard interfaces - Realm Management Interface (RMI) - to the
> >> Normal world hypervisor to manage the VMs running in the Realm world (also called
> >> Realms in short). These are exposed via SMC and are routed through the EL3
> >> firmwre.
> >> The RMI interface includes:
> >>    - Move a physical page from the Normal world to the Realm world
> >>    - Creating a Realm with requested parameters, tracked via Realm Descriptor (RD)
> >>    - Creating VCPUs aka Realm Execution Context (REC), with initial register state.
> >>    - Create stage2 translation table at any level.
> >>    - Load initial images into Realm Memory from normal world memory
> >>    - Schedule RECs (vCPUs) and handle exits
> >>    - Inject virtual interrupts into the Realm
> >>    - Service stage2 runtime faults with pages (provided by host, scrubbed by RMM).
> >>    - Create "shared" mappings that can be accessed by VMM/Hyp.
> >>    - Reclaim the memory allocated for the RAM and RTTs (Realm Translation Tables)
> >>
> >> However v1.0 of RMM specifications doesn't support:
> >>   - Paging protected memory of a Realm VM. Thus the pages backing the protected
> >>     memory region must be pinned.
> >>   - Live migration of Realms.
> >>   - Trusted Device assignment.
> >>   - Physical interrupt backed Virtual interrupts for Realms
> >>
> >> RMM also provides certain services to the Realms via SMC, called Realm Service
> >> Interface (RSI). These include:
> >>   - Realm Guest Configuration.
> >>   - Attestation & Measurement services
> >>   - Managing the state of an Intermediate Physical Address (IPA aka GPA) page.
> >>   - Host Call service (Communication with the Normal world Hypervisor)
> >>
> >> The specifications for the RMM software is currently at *v1.0-Beta2* and the
> >> latest version is available here [1].
> >>
> >> The Trusted Firmware foundation has an implementation of the RMM - TF-RMM -
> >> available here [3].
> >>
> >> Implementation
> >> =================
> >>
> >> This version of the stack is based on the RMM specification v1.0-Beta0[2], with
> >> following exceptions :
> >>    - TF-RMM/KVM currently doesn't support the optional features of PMU,
> >>       SVE and Self-hosted debug (coming soon).
> >>    - The RSI_HOST_CALL structure alignment requirement is reduced to match
> >>       RMM v1.0 Beta1
> >>    - RMI/RSI version numbers do not match the RMM spec. This will be
> >>      resolved once the spec/implementation is complete, across TF-RMM+Linux stack.
> >>
> >> We plan to update the stack to support the latest version of the RMMv1.0 spec
> >> in the coming revisions.
> >>
> >> This release includes the following components :
> >>
> >>   a) Linux Kernel
> >>       i) Host / KVM support - Support for driving the Realms via RMI. This is
> >>       dependent on running in the Kernel at EL2 (aka VHE mode). Also provides
> >>       UABI for VMMs to manage the Realm VMs. The support is restricted to 4K page
> >>       size, matching the Stage2 granule supported by RMM. The VMM is responsible
> >>       for making sure the guest memory is locked.
> >>
> >>         TODO: Guest Private memory[10] integration - We have been following the
> >>         series and support will be added once it is merged upstream.
> >>       
> >>       ii) Guest support - Support for a Linux Kernel to run in the Realm VM at
> >>       Realm-EL1, using RSI services. This includes virtio support (virtio-v1.0
> >>       only). All I/O are treated as non-secure/shared.
> >>   
> >>   c) kvmtool - VMM changes required to manage Realm VMs. No guest private memory
> >>      as mentioned above.
> >>   d) kvm-unit-tests - Support for running in Realms along with additional tests
> >>      for RSI ABI.
> >>
> >> Running the stack
> >> ====================
> >>
> >> To run/test the stack, you would need the following components :
> >>
> >> 1) FVP Base AEM RevC model with FEAT_RME support [4]
> >> 2) TF-A firmware for EL3 [5]
> >> 3) TF-A RMM for R-EL2 [3]
> >> 4) Linux Kernel [6]
> >> 5) kvmtool [7]
> >> 6) kvm-unit-tests [8]
> >>
> >> Instructions for building the firmware components and running the model are
> >> available here [9]. Once, the host kernel is booted, a Realm can be launched by
> >> invoking the `lkvm` commad as follows:
> >>
> >>   $ lkvm run --realm 				 \
> >> 	 --measurement-algo=["sha256", "sha512"] \
> >> 	 --disable-sve				 \
> >> 	 <normal-vm-options>
> >>
> >> Where:
> >>   * --measurement-algo (Optional) specifies the algorithm selected for creating the
> >>     initial measurements by the RMM for this Realm (defaults to sha256).
> >>   * GICv3 is mandatory for the Realms.
> >>   * SVE is not yet supported in the TF-RMM, and thus must be disabled using
> >>     --disable-sve
> >>
> >> You may also run the kvm-unit-tests inside the Realm world, using the similar
> >> options as above.
> >>
> >>
> >> Links
> >> ============
> >>
> >> [0] Arm CCA Landing page (See Key Resources section for various documentations)
> >>      https://www.arm.com/architecture/security-features/arm-confidential-compute-architecture
> >>
> >> [1] RMM Specification Latest
> >>      https://developer.arm.com/documentation/den0137/latest
> >>
> >> [2] RMM v1.0-Beta0 specification
> >>      https://developer.arm.com/documentation/den0137/1-0bet0/
> >>
> >> [3] Trusted Firmware RMM - TF-RMM
> >>      https://www.trustedfirmware.org/projects/tf-rmm/
> >>      GIT: https://git.trustedfirmware.org/TF-RMM/tf-rmm.git
> >>
> >> [4] FVP Base RevC AEM Model (available on x86_64 / Arm64 Linux)
> >>      https://developer.arm.com/Tools%20and%20Software/Fixed%20Virtual%20Platforms
> >>
> >> [5] Trusted Firmware for A class
> >>      https://www.trustedfirmware.org/projects/tf-a/
> >>
> >> [6] Linux kernel support for Arm-CCA
> >>      https://gitlab.arm.com/linux-arm/linux-cca
> >>      Host Support branch:	cca-host/rfc-v1
> >>      Guest Support branch:	cca-guest/rfc-v1
> >>
> >> [7] kvmtool support for Arm CCA
> >>      https://gitlab.arm.com/linux-arm/kvmtool-cca cca/rfc-v1
> >>
> >> [8] kvm-unit-tests support for Arm CCA
> >>      https://gitlab.arm.com/linux-arm/kvm-unit-tests-cca  cca/rfc-v1
> >>
> >> [9] Instructions for Building Firmware components and running the model, see
> >>      section 4.19.2 "Building and running TF-A with RME"
> >>      https://trustedfirmware-a.readthedocs.io/en/latest/components/realm-management-extension.html#building-and-running-tf-a-with-rme
> >>
> >> [10] fd based Guest Private memory for KVM
> >>     https://lkml.kernel.org/r/20221202061347.1070246-1-chao.p.peng@xxxxxxxxxxxxxxx
> >>
> >> Cc: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> >> Cc: Andrew Jones <andrew.jones@xxxxxxxxx>
> >> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> >> Cc: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> >> Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
> >> Cc: Fuad Tabba <tabba@xxxxxxxxxx>
> >> Cc: James Morse <james.morse@xxxxxxx>
> >> Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> >> Cc: Joey Gouly <Joey.Gouly@xxxxxxx>
> >> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> >> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> >> Cc: Oliver Upton <oliver.upton@xxxxxxxxx>
> >> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >> Cc: Quentin Perret <qperret@xxxxxxxxxx>
> >> Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> >> Cc: Steven Price <steven.price@xxxxxxx>
> >> Cc: Thomas Huth <thuth@xxxxxxxxxx>
> >> Cc: Will Deacon <will@xxxxxxxxxx>
> >> Cc: Zenghui Yu <yuzenghui@xxxxxxxxxx>
> >> To: linux-coco@xxxxxxxxxxxxxxx
> >> To: kvmarm@xxxxxxxxxxxxxxx
> >> Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
> >> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> >> To: linux-kernel@xxxxxxxxxxxxxxx
> >> To: kvm@xxxxxxxxxxxxxxx
> >>
> >> _______________________________________________
> >> linux-arm-kernel mailing list
> >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel  
> >   
> 
>