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OpenBMC/meta-arm/meta-arm-bsp/documentation/fvp-baser-aemv8r64.md
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2026-04-23 17:07:55 +08:00

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Armv8-R AArch64 AEM FVP Support in meta-arm-bsp

Overview

Fixed Virtual Platforms (FVP) are complete simulations of an Arm system, including processor, memory and peripherals. These are set out in a "programmer's view", which gives you a comprehensive model on which to build and test your software.

The Armv8-R AEM FVP is a free of charge Armv8-R Fixed Virtual Platform. It supports the latest Armv8-R feature set.

This BSP implements a reference stack for the AArch64 support in the R-class first announced with the Cortex-R82 processor: https://developer.arm.com/ip-products/processors/cortex-r/cortex-r82

Fast Models Fixed Virtual Platforms (FVP) Reference Guide: https://developer.arm.com/docs/100966/latest

BSP Support

The fvp-baser-aemv8r64 Yocto MACHINE supports the following BSP components, where either a standard or Real-Time Linux kernel (PREEMPT_RT) can be built and run:

  • FVP_Base_AEMv8R: v11.20.15
  • boot-wrapper-aarch64: provides PSCI support
  • U-Boot: v2022.07 - provides UEFI services
  • Linux kernel: linux-yocto-5.15
  • Linux kernel with PREEMPT_RT support: linux-yocto-rt-5.15

Note that the Real-Time Linux kernel (PREEMPT_RT) does not use the real-time architectural extensions of the Armv8-R feature set.

High-Level Architecture

The diagram below shows the current boot flow:

+---------------------------------------------------------------+
|                         Linux kernel                          |
+---------------------------------------------------------------+
           /|\                                     /|\
            |                                       |
            | UEFI services                         |
            |                         PSCI services |
           \|/                                      |
    +----------------+                              |     S-EL1
----|     U-Boot     |------------------------------|-----------
    +----------------+                              |     S-EL2
           /|\                                      |
            |                                       |
            |                                       |
            |                                       |
+--------------------------------------------------\|/----------+
|                        +----------------+ +----------------+  |
|  boot-wrapper-aarch64  |  Device tree   | |  PSCI handler  |  |
|                        +----------------+ +----------------+  |
+---------------------------------------------------------------+

The firmware binary (generated as linux-system.axf) includes boot-wrapper-aarch64, the flattened device tree and U-Boot. U-Boot is configured to automatically detect a virtio block device and boot the UEFI payload at the path /efi/boot/bootaa64.efi. Using the standard build, the first partition contains a Grub image at this path, which boots the Linux kernel at /Image on the same partition. The second partition of the image contains the Linux root file system.

There is no EL3 or non-secure world in the Armv8-R AArch64 architecture, so the reset vector starts boot-wrapper-aarch64 at S-EL2. Boot-wrapper-aarch64 is compiled with the --enable-keep-el flag, which causes it to boot U-Boot at S-EL2 too. U-Boot is compiled with the CONFIG_ARMV8_SWITCH_TO_EL1 flag, which causes it to switch to S-EL1 before booting Linux.

The bundled device tree is passed to U-Boot via register x0. U-Boot passes the same device tree to Linux via the UEFI system table.

Power state management is provided by PSCI services in boot-wrapper-aarch64. Linux accesses the PSCI handler via HVC calls to S-EL2. U-Boot has been patched to prevent it from overriding the exception vector at S-EL2. The PSCI handler memory region is added to a /memreserve/ node in the device tree.

Please note that the final firmware architecture for the fvp-baser-aemv8r64 is not yet stabilized. The patches in this layer are provided for development and evaluation purposes only, and should not be used in production firmware.

Quick start: Howto Build and Run

Host environment setup

The following instructions have been tested on hosts running Ubuntu 18.04 and Ubuntu 20.04. Install the required packages for the build host: https://docs.yoctoproject.org/singleindex.html#required-packages-for-the-build-host

Kas is a setup tool for bitbake based projects. The minimal supported version is 3.0, install it like so:

pip3 install --user --upgrade kas

For more details on kas, see https://kas.readthedocs.io/.

To build the images for the fvp-baser-aemv8r64 machine, you also need to accept the EULA at https://developer.arm.com/downloads/-/arm-ecosystem-fvps/eula by setting the following environment variable:

ARM_FVP_EULA_ACCEPT="True"

Note: The host machine should have at least 50 GBytes of free disk space for the next steps to work correctly.

Fetch sources

To fetch and build the ongoing development of the software stack follow the instructions on this document.

To fetch and build the version 1 (single core) find instructions at https://community.arm.com/developer/tools-software/oss-platforms/w/docs/633/release-1-single-core

To fetch and build the version 2 (linux smp) find instructions at https://community.arm.com/developer/tools-software/oss-platforms/w/docs/634/release-2---smp

Fetch the meta-arm repository into a build directory:

mkdir -p ~/fvp-baser-aemv8r64-build
cd ~/fvp-baser-aemv8r64-build
git clone https://git.yoctoproject.org/git/meta-arm

Build

Building with the standard Linux kernel:

cd ~/fvp-baser-aemv8r64-build
export ARM_FVP_EULA_ACCEPT="True"
kas build meta-arm/kas/fvp-baser-aemv8r64-bsp.yml

Building with the Real-Time Linux kernel (PREEMPT_RT):

cd ~/fvp-baser-aemv8r64-build
export ARM_FVP_EULA_ACCEPT="True"
kas build meta-arm/kas/fvp-baser-aemv8r64-rt-bsp.yml

Run

To run an image after the build is done with the standard Linux kernel:

kas shell --keep-config-unchanged \
   meta-arm/kas/fvp-baser-aemv8r64-bsp.yml \
       --command "../layers/meta-arm/scripts/runfvp \
       --console "

To run an image after the build is done with the Real-Time Linux kernel (PREEMPT_RT):

kas shell --keep-config-unchanged \
   meta-arm/kas/fvp-baser-aemv8r64-rt-bsp.yml \
       --command "../layers/meta-arm/scripts/runfvp \
       --console "

Note: The terminal console login is root without password.

To finish the fvp emulation, you need to close the telnet session:

  • Escape to telnet console with ctrl+].
  • Run quit to close the session.

Networking

The FVP is configured by default to use "user-mode networking", which simulates an IP router and DHCP server to avoid additional host dependencies and networking configuration. Outbound connections work automatically, e.g. by running:

wget www.arm.com

Inbound connections require an explicit port mapping from the host. By default, port 8022 on the host is mapped to port 22 on the FVP, so that the following command will connect to an ssh server running on the FVP:

ssh root@localhost -p 8022

Note that user-mode networking does not support ICMP, so ping will not work. For more information about user-mode networking, please see https://developer.arm.com/documentation/100964/1117/Introduction-to-Fast-Models/User-mode-networking?lang=en

File sharing between host and fvp

It is possible to share a directory between the host machine and the fvp using the virtio P9 device component included in the kernel. To do so, create a directory to be mounted from the host machine:

mkdir /path/to/host-mount-dir

Then, add the following parameter containing the path to the directory when launching the model:

--parameter 'bp.virtiop9device.root_path=/path/to/host-mount-dir'

e.g. for the standard Linux kernel:

kas shell --keep-config-unchanged \
   meta-arm/kas/fvp-baser-aemv8r64-bsp.yml \
       --command "../layers/meta-arm/scripts/runfvp \
       --console -- --parameter \
       'bp.virtiop9device.root_path=/path/to/host-mount-dir'"

Once you are logged into the fvp, the host directory can be mounted in a directory on the model using the following command:

mount -t 9p -o trans=virtio,version=9p2000.L FM /path/to/fvp-mount-dir

Devices supported in the kernel

  • serial
  • virtio 9p
  • virtio disk
  • virtio network
  • virtio rng
  • watchdog
  • rtc

Known Issues and Limitations

  • Only PSCI CPU_ON and CPU_OFF functions are supported
  • Linux kernel does not support booting from secure EL2 on Armv8-R AArch64
  • Linux KVM does not support Armv8-R AArch64
  • Device DMA memory cache-coherence issue: the FVP cache_state_modelled parameter will affect the cache coherence behavior of peripherals’ DMA. When users set cache_state_modelled=1, they also have to set cci400.force_on_from_start=1 to force the FVP to enable snooping on upstream ports.

Change Log

  • Enabled the ability for U-Boot to apply device tree overlays
  • Fixed bug in U-Boot that caused changes to the memory node in the device tree to be ignored.
  • Added boot-wrapper-aarch64 support for booting SMP payloads at S-EL2.
  • Enabled testimage support by default.
  • Added virtio_rng to improve random number generation.
  • Added U-Boot v2022.01 for UEFI support.
  • Updated Linux kernel version from 5.14 to 5.15 for both standard and Real-Time (PREEMPT_RT) builds.
  • Updated boot-wrapper-aarch64 revision and added support for booting U-Boot.
  • Included boot-wrapper-aarch64 PSCI services in /memreserve/ region.
  • Fixed the counter frequency initialization in boot-wrapper-aarch64.
  • Configured the FVP to use the default RAM size of 4 Gb
  • Fixed PL011 and SP805 register sizes in the device tree.
  • Added virtio_net User Networking mode by default and removed instructions about tap networking setup.
  • Updated Linux kernel version from 5.10 to 5.14 for both standard and Real-Time (PREEMPT_RT) builds.
  • Enabled SMP support via boot-wrapper-aarch64 providing the PSCI CPU_ON and CPU_OFF functions.
  • Introduced Armv8-R64 compiler flags.
  • Added Linux PREEMPT_RT support via linux-yocto-rt-5.10.
  • Added support for file sharing with the host machine using Virtio P9.
  • Added support for runfvp.
  • Added performance event support (PMU) in the Linux device tree.
  • Introduced the fvp-baser-aemv8r64 machine and its BSP composed of boot-wrapper-aarch64 and linux-yocto-5.10 supporting serial, virtio disk, virtio network, watchdog and rtc.
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