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Armv8-R AArch64 AEM FVP Support in meta-arm-bsp
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===============================================
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Overview
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--------
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Fixed Virtual Platforms (FVP) are complete simulations of an Arm system,
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including processor, memory and peripherals. These are set out in a
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"programmer's view", which gives you a comprehensive model on which to build
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and test your software.
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The Armv8-R AEM FVP is a free of charge Armv8-R Fixed Virtual Platform. It
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supports the latest Armv8-R feature set.
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This BSP implements a reference stack for the AArch64 support in the R-class
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first announced with the Cortex-R82 processor:
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https://developer.arm.com/ip-products/processors/cortex-r/cortex-r82
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Fast Models Fixed Virtual Platforms (FVP) Reference Guide:
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https://developer.arm.com/docs/100966/latest
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BSP Support
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-----------
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The fvp-baser-aemv8r64 Yocto MACHINE supports the following BSP components,
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where either a standard or Real-Time Linux kernel (PREEMPT\_RT) can be built
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and run:
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- FVP_Base_AEMv8R: v11.20.15
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- boot-wrapper-aarch64: provides PSCI support
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- U-Boot: v2022.07 - provides UEFI services
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- Linux kernel: linux-yocto-5.15
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- Linux kernel with PREEMPT\_RT support: linux-yocto-rt-5.15
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Note that the Real-Time Linux kernel (PREEMPT\_RT) does not use the real-time
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architectural extensions of the Armv8-R feature set.
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High-Level Architecture
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-----------------------
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The diagram below shows the current boot flow:
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+---------------------------------------------------------------+
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| Linux kernel |
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+---------------------------------------------------------------+
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/|\ /|\
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| |
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| UEFI services |
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| PSCI services |
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\|/ |
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+----------------+ | S-EL1
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----| U-Boot |------------------------------|-----------
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+----------------+ | S-EL2
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/|\ |
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+--------------------------------------------------\|/----------+
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| +----------------+ +----------------+ |
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| boot-wrapper-aarch64 | Device tree | | PSCI handler | |
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| +----------------+ +----------------+ |
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+---------------------------------------------------------------+
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The firmware binary (generated as `linux-system.axf`) includes
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boot-wrapper-aarch64, the flattened device tree and U-Boot. U-Boot is configured
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to automatically detect a virtio block device and boot the UEFI payload at the
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path `/efi/boot/bootaa64.efi`. Using the standard build, the first partition
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contains a Grub image at this path, which boots the Linux kernel at `/Image` on
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the same partition. The second partition of the image contains the Linux root
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file system.
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There is no EL3 or non-secure world in the Armv8-R AArch64 architecture, so the
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reset vector starts boot-wrapper-aarch64 at S-EL2. Boot-wrapper-aarch64 is
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compiled with the `--enable-keep-el` flag, which causes it to boot U-Boot at
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S-EL2 too. U-Boot is compiled with the `CONFIG_ARMV8_SWITCH_TO_EL1` flag, which
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causes it to switch to S-EL1 before booting Linux.
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The bundled device tree is passed to U-Boot via register x0. U-Boot passes the
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same device tree to Linux via the UEFI system table.
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Power state management is provided by PSCI services in boot-wrapper-aarch64.
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Linux accesses the PSCI handler via HVC calls to S-EL2. U-Boot has been patched
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to prevent it from overriding the exception vector at S-EL2. The PSCI handler
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memory region is added to a `/memreserve/` node in the device tree.
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Please note that the final firmware architecture for the fvp-baser-aemv8r64 is
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not yet stabilized. The patches in this layer are provided for development and
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evaluation purposes only, and should not be used in production firmware.
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Quick start: Howto Build and Run
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--------------------------------
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### Host environment setup
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The following instructions have been tested on hosts running Ubuntu 18.04 and
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Ubuntu 20.04.
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Install the required packages for the build host:
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https://docs.yoctoproject.org/singleindex.html#required-packages-for-the-build-host
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Kas is a setup tool for bitbake based projects. The minimal supported version
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is 3.0, install it like so:
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pip3 install --user --upgrade kas
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For more details on kas, see https://kas.readthedocs.io/.
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To build the images for the fvp-baser-aemv8r64 machine, you also need to accept
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the EULA at
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https://developer.arm.com/downloads/-/arm-ecosystem-fvps/eula
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by setting the following environment variable:
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ARM_FVP_EULA_ACCEPT="True"
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**Note:** The host machine should have at least 50 GBytes of free disk space
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for the next steps to work correctly.
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### Fetch sources
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To fetch and build the ongoing development of the software stack follow the
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instructions on this document.
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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
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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
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Fetch the meta-arm repository into a build directory:
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mkdir -p ~/fvp-baser-aemv8r64-build
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cd ~/fvp-baser-aemv8r64-build
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git clone https://git.yoctoproject.org/git/meta-arm
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### Build
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Building with the standard Linux kernel:
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cd ~/fvp-baser-aemv8r64-build
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export ARM_FVP_EULA_ACCEPT="True"
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kas build meta-arm/kas/fvp-baser-aemv8r64-bsp.yml
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Building with the Real-Time Linux kernel (PREEMPT\_RT):
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cd ~/fvp-baser-aemv8r64-build
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export ARM_FVP_EULA_ACCEPT="True"
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kas build meta-arm/kas/fvp-baser-aemv8r64-rt-bsp.yml
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### Run
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To run an image after the build is done with the standard Linux kernel:
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kas shell --keep-config-unchanged \
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meta-arm/kas/fvp-baser-aemv8r64-bsp.yml \
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--command "../layers/meta-arm/scripts/runfvp \
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--console "
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To run an image after the build is done with the Real-Time Linux kernel
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(PREEMPT\_RT):
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kas shell --keep-config-unchanged \
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meta-arm/kas/fvp-baser-aemv8r64-rt-bsp.yml \
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--command "../layers/meta-arm/scripts/runfvp \
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--console "
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**Note:** The terminal console login is `root` without password.
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To finish the fvp emulation, you need to close the telnet session:
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- Escape to telnet console with ``ctrl+]``.
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- Run ``quit`` to close the session.
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### Networking
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The FVP is configured by default to use "user-mode networking", which simulates
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an IP router and DHCP server to avoid additional host dependencies and
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networking configuration. Outbound connections work automatically, e.g. by
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running:
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wget www.arm.com
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Inbound connections require an explicit port mapping from the host. By default,
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port 8022 on the host is mapped to port 22 on the FVP, so that the following
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command will connect to an ssh server running on the FVP:
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ssh root@localhost -p 8022
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Note that user-mode networking does not support ICMP, so `ping` will not work.
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For more information about user-mode networking, please see
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https://developer.arm.com/documentation/100964/1117/Introduction-to-Fast-Models/User-mode-networking?lang=en
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### File sharing between host and fvp
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It is possible to share a directory between the host machine and the fvp using
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the virtio P9 device component included in the kernel. To do so, create a
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directory to be mounted from the host machine:
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mkdir /path/to/host-mount-dir
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Then, add the following parameter containing the path to the directory when
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launching the model:
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--parameter 'bp.virtiop9device.root_path=/path/to/host-mount-dir'
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e.g. for the standard Linux kernel:
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kas shell --keep-config-unchanged \
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meta-arm/kas/fvp-baser-aemv8r64-bsp.yml \
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--command "../layers/meta-arm/scripts/runfvp \
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--console -- --parameter \
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'bp.virtiop9device.root_path=/path/to/host-mount-dir'"
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Once you are logged into the fvp, the host directory can be mounted in a
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directory on the model using the following command:
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mount -t 9p -o trans=virtio,version=9p2000.L FM /path/to/fvp-mount-dir
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Devices supported in the kernel
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-------------------------------
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- serial
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- virtio 9p
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- virtio disk
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- virtio network
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- virtio rng
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- watchdog
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- rtc
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Known Issues and Limitations
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----------------------------
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- Only PSCI CPU\_ON and CPU\_OFF functions are supported
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- Linux kernel does not support booting from secure EL2 on Armv8-R AArch64
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- Linux KVM does not support Armv8-R AArch64
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- Device DMA memory cache-coherence issue: the FVP `cache_state_modelled`
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parameter will affect the cache coherence behavior of peripherals’ DMA. When
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users set `cache_state_modelled=1`, they also have to set
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`cci400.force_on_from_start=1` to force the FVP to enable snooping on upstream
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ports.
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Change Log
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----------
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- Enabled the ability for U-Boot to apply device tree overlays
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- Fixed bug in U-Boot that caused changes to the `memory` node in the device
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tree to be ignored.
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- Added boot-wrapper-aarch64 support for booting SMP payloads at S-EL2.
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- Enabled testimage support by default.
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- Added virtio\_rng to improve random number generation.
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- Added U-Boot v2022.01 for UEFI support.
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- Updated Linux kernel version from 5.14 to 5.15 for both standard and
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Real-Time (PREEMPT\_RT) builds.
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- Updated boot-wrapper-aarch64 revision and added support for booting U-Boot.
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- Included boot-wrapper-aarch64 PSCI services in `/memreserve/` region.
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- Fixed the counter frequency initialization in boot-wrapper-aarch64.
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- Configured the FVP to use the default RAM size of 4 Gb
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- Fixed PL011 and SP805 register sizes in the device tree.
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- Added virtio\_net User Networking mode by default and removed instructions
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about tap networking setup.
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- Updated Linux kernel version from 5.10 to 5.14 for both standard and
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Real-Time (PREEMPT\_RT) builds.
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- Enabled SMP support via boot-wrapper-aarch64 providing the PSCI CPU\_ON and
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CPU\_OFF functions.
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- Introduced Armv8-R64 compiler flags.
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- Added Linux PREEMPT\_RT support via linux-yocto-rt-5.10.
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- Added support for file sharing with the host machine using Virtio P9.
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- Added support for runfvp.
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- Added performance event support (PMU) in the Linux device tree.
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- Introduced the fvp-baser-aemv8r64 machine and its BSP composed of
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boot-wrapper-aarch64 and linux-yocto-5.10 supporting serial, virtio disk,
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virtio network, watchdog and rtc.
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