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

Jonathan Cameron
2023-07-14T16:28:44Z

On Fri, 14 Jul 2023 16:03:37 +0100
Suzuki K Poulose <suzuki.poulose@arm.com> 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@arm.com> 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@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: 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: kvmarm@lists.cs.columbia.edu
> >> Cc: linux-arm-kernel@lists.infradead.org
> >> To: linux-kernel@vger.kernel.org
> >> To: kvm@vger.kernel.org
> >>
> >> _______________________________________________
> >> linux-arm-kernel mailing list
> >> linux-arm-kernel@lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >
>
>