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

Suzuki K Poulose
2024-01-10T11:41:25Z

Hi Itaru,

On 10/01/2024 05:40, Itaru Kitayama wrote:
> On Mon, Oct 02, 2023 at 01:43:11PM +0100, Suzuki K Poulose wrote:
>> Hi,
>>
>>
>>> 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
>>>
>>
>> We have updated the stack for Arm CCA Linux support to RMM-v1.0-EAC2 (See links)
>> We are not posting the patches for review yet, as we plan to update our
>> stack to support the latest RMM-v1.0 specification, which includes some
>> functional changes to support PSCI monitoring by the VMM along with other
>> minor changes. All relevant components are updated on a new branch "rmm-v1.0-eac2"
>> Guest-mem support is not included, but is in progress.
>>
>> Change log :
>> - KVM RMI support updated to v1.0-eac2, with optimisations to stage2 tear down
>> - Guest (Linux and kvm-unit-test) support for RSI compliant to v1.0-eac2
>> - SVE, PMU support for Realms
>>
>> kvmtool :
>> - Dropped no-compat and switched to --loglevel (merged upstream)
>> - Support for SVE, --sve-vl for vector length
>>
>>> 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 \
>>
>> As noted above, this is no longer required.
>>
>>> <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/
>>
>> EAC2 spec: https://developer.arm.com/documentation/den0137/1-0eac2/
>>>
>>> [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
>>
>> Update branch : cca-host/rmm-v1.0-eac2
>>
>>> Guest Support branch: cca-guest/rfc-v1
>>
>> Update branch : cca-guest/rmm-v1.0-eac2
>>
>> Combined tree for host and guest is also available at: "cca-full/rmm-v1.0-eac2"
>>
>>>
>>> [7] kvmtool support for Arm CCA
>>> https://gitlab.arm.com/linux-arm/kvmtool-cca cca/rfc-v1
>>
>> Update branch : cca/rmm-v1.0-eac2
>>
>>>
>>> [8] kvm-unit-tests support for Arm CCA
>>> https://gitlab.arm.com/linux-arm/kvm-unit-tests-cca cca/rfc-v1
>>>
>>
>> Update branch : cca/rmm-v1.0-eac2
>>
>>
>> Suzuki
>>
>>> [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@linux.intel.com
>>
>>
>>
>>
>>
>> Cc: Alexandru Elisei <alexandru.elisei@arm.com>
>> Cc: Andrew Jones <andrew.jones@linux.dev>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Chao Peng <chao.p.peng@linux.intel.com>
>> Cc: Christoffer Dall <christoffer.dall@arm.com>
>> Cc: Fuad Tabba <tabba@google.com>
>> Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
>> Cc: James Morse <james.morse@arm.com>
>> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
>> Cc: Joey Gouly <Joey.Gouly@arm.com>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Oliver Upton <oliver.upton@linux.dev>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Quentin Perret <qperret@google.com>
>> Cc: Sean Christopherson <seanjc@google.com>
>> Cc: Steven Price <steven.price@arm.com>
>> Cc: Thomas Huth <thuth@redhat.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Zenghui Yu <yuzenghui@huawei.com>
>> To: linux-coco@lists.linux.dev
>> To: kvmarm@lists.linux.dev
>> Cc: linux-arm-kernel@lists.infradead.org
>> To: linux-kernel@vger.kernel.org
>> To: kvm@vger.kernel.org
>
> Suzuki,
> Any update to the Arm CCA series (v3?) since last October?

Yes, we now have a version that supports the final RMM-v1.0
specification (RMM-v1.0-EAC5). We also have the UEFI EDK2 firmware
support for Guests in Realm world.

We are planning to post the changes for review in the v6.8-rc cycle. We
are trying to integrate the guest_mem support (available in v6.8-rc1) as
well as reusing some of the arm64 kvm generic interface for configuring
the Realm parameters (e.g., PMU, SVE_VL etc).

Here is a version that is missing the items mentioned above, based
on v6.7-rc4, if anyone would like to try.

Also, the easiest way to get the components built and model kick started
is using the shrinkwrap [6] tool, using the cca-3world configuration.
The tool pulls all the required software components, builds (including
the buildroot for rootfs) and can run a model using these built
components.

[0] Linux Repo:
Where: git@git.gitlab.arm.com:linux-arm/linux-cca.git
KVM Support branch: cca-host/rmm-v1.0-eac5
Linux Guest branch: cca-guest/rmm-v1.0-eac5
Full stack branch: cca-full/rmm-v1.0-eac5

[1] kvmtool Repo:
Where: git@git.gitlab.arm.com:linux-arm/kvmtool-cca.git
Branch: cca/rmm-v1.0-eac5

[2] kvm-unit-tests Repo:
Where: git@git.gitlab.arm.com:linux-arm/kvm-unit-tests-cca.git
Branch: cca/rmm-v1.0-eac5

[3] UEFI Guest firmware:
edk2: https://git.gitlab.arm.com/linux-arm/edk2-cca.git
revision: 2802_arm_cca_rmm-v1.0-eac5

edk2-platforms:
https://git.gitlab.arm.com/linux-arm/edk2-platforms-cca.git
revision: 2802_arm_cca_rmm-v1.0-eac5

[4] RMM Repo:
Where: https://git.trustedfirmware.org/TF-RMM/tf-rmm.git
tag : tf-rmm-v0.4.0

[5] TF-A repo:
Where: https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
Tag: v2.10

[6] https://shrinkwrap.docs.arm.com/en/latest/
config: cca-3world.yaml

Kind regards
Suzuki