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Release 3 - UEFI

Changes Since Release 2 - SMP

  • Added U-Boot v2021.07 for UEFI support
  • 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

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:

  • boot-wrapper-aarch64: provides PSCI support
  • U-Boot: v2021.07: provides UEFI services
  • Linux kernel: linux-yocto-5.14

  • Linux kernel with PREEMPT_RT support: linux-yocto-rt-5.14

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:

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 meta-arm-bsp are provided for development and evaluation purposes only, and should not be used in production firmware.

Quick start: How to 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 2.6, install it like so:

$ pip3 install --user --upgrade kas

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

To build the images for fvp-base machine, you also need to:

  • Download the FVP_Base_AEMv8R_11.17_21.tgz  image AEM V8-R FVP Installer (Linux) package from Arm's website. You need to have an account and be logged in to be able to download it.
  • Set absolute path to the FVP_Base_AEMv8R_11.17_21.tgz  downloaded package in FVP_BASE_R_AEM_TARBALL_URI 
  • Accept EULA in FVP_BASE_R_ARM_EULA_ACCEPT 

The variables should be set like so:

$ FVP_BASE_R_AEM_TARBALL_URI="file:///absolute/path/to/FVP_Base_AEMv8R_11.17_21.tgz"
$ FVP_BASE_R_ARM_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 -b honister

Build

Building with the standard Linux kernel:

$ cd ~/fvp-baser-aemv8r64-build
$ export FVP_BASE_R_AEM_TARBALL_URI="file:///absolute/path/to/FVP_Base_AEMv8R_11.17_21.tgz"
$ export FVP_BASE_R_ARM_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 FVP_BASE_R_AEM_TARBALL_URI="file:///absolute/path/to/FVP_Base_AEMv8R_11.17_21.tgz"
$ export FVP_BASE_R_ARM_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
  • virtual 9p
  • virtio disk
  • virtio network
  • 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.