[RFC] Support for Arm CCA VMs on Linux
Itaru Kitayama
itaru.kitayama at linux.dev
Tue Jan 9 21:40:01 PST 2024
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 at arm.com>
> Cc: Andrew Jones <andrew.jones at linux.dev>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Chao Peng <chao.p.peng at linux.intel.com>
> Cc: Christoffer Dall <christoffer.dall at arm.com>
> Cc: Fuad Tabba <tabba at google.com>
> Cc: Jonathan Cameron <jonathan.cameron at huawei.com>
> Cc: James Morse <james.morse at arm.com>
> Cc: Jean-Philippe Brucker <jean-philippe at linaro.org>
> Cc: Joey Gouly <Joey.Gouly at arm.com>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Oliver Upton <oliver.upton at linux.dev>
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Quentin Perret <qperret at google.com>
> Cc: Sean Christopherson <seanjc at google.com>
> Cc: Steven Price <steven.price at arm.com>
> Cc: Thomas Huth <thuth at redhat.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Zenghui Yu <yuzenghui at huawei.com>
> To: linux-coco at lists.linux.dev
> To: kvmarm at lists.linux.dev
> Cc: linux-arm-kernel at lists.infradead.org
> To: linux-kernel at vger.kernel.org
> To: kvm at vger.kernel.org
Suzuki,
Any update to the Arm CCA series (v3?) since last October?
Thanks,
Itaru.
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