QEMU virt Armv8-A
=================

Trusted Firmware-A (TF-A) implements the EL3 firmware layer for QEMU virt
Armv8-A. BL1 is used as the BootROM, supplied with the -bios argument.
When QEMU starts all CPUs are released simultaneously, BL1 selects a
primary CPU to handle the boot and the secondaries are placed in a polling
loop to be released by normal world via PSCI.

BL2 edits the Flattened Device Tree, FDT, generated by QEMU at run-time to
add a node describing PSCI and also enable methods for the CPUs.

If ``ARM_LINUX_KERNEL_AS_BL33`` is set to 1 then this FDT will be passed to BL33
via register x0, as expected by a Linux kernel. This allows a Linux kernel image
to be booted directly as BL33 rather than using a bootloader.

An ARM64 defconfig v5.5 Linux kernel is known to boot, FDT doesn't need to be
provided as it's generated by QEMU.

Current limitations:

-  Only cold boot is supported

Getting non-TF images
---------------------

``QEMU_EFI.fd`` can be downloaded from
http://snapshots.linaro.org/components/kernel/leg-virt-tianocore-edk2-upstream/latest/QEMU-KERNEL-AARCH64/RELEASE_GCC5/QEMU_EFI.fd

or, can be built as follows:

.. code:: shell

    git clone https://github.com/tianocore/edk2.git
    cd edk2
    git submodule update --init
    make -C BaseTools
    source edksetup.sh
    export GCC5_AARCH64_PREFIX=aarch64-linux-gnu-
    build -a AARCH64 -t GCC5 -p ArmVirtPkg/ArmVirtQemuKernel.dsc

````

Then, you will get ``Build/ArmVirtQemuKernel-AARCH64/DEBUG_GCC5/FV/QEMU_EFI.fd``

Please note you do not need to use GCC 5 in spite of the environment variable
``GCC5_AARCH64_PREFIX``.

The rootfs can be built by using Buildroot as follows:

.. code:: shell

    git clone git://git.buildroot.net/buildroot.git
    cd buildroot
    make qemu_aarch64_virt_defconfig
    utils/config -e BR2_TARGET_ROOTFS_CPIO
    utils/config -e BR2_TARGET_ROOTFS_CPIO_GZIP
    make olddefconfig
    make

Then, you will get ``output/images/rootfs.cpio.gz``.

Booting via semi-hosting option
-------------------------------

Boot binaries, except BL1, are primarily loaded via semi-hosting so all
binaries has to reside in the same directory as QEMU is started from. This
is conveniently achieved with symlinks the local names as:

-  ``bl2.bin`` -> BL2
-  ``bl31.bin`` -> BL31
-  ``bl33.bin`` -> BL33 (``QEMU_EFI.fd``)
-  ``Image`` -> linux/arch/arm64/boot/Image

To build:

.. code:: shell

    make CROSS_COMPILE=aarch64-none-elf- PLAT=qemu

To start (QEMU v5.0.0):

.. code:: shell

    qemu-system-aarch64 -nographic -machine virt,secure=on -cpu cortex-a57  \
        -kernel Image                           \
        -append "console=ttyAMA0,38400 keep_bootcon"   \
        -initrd rootfs.cpio.gz -smp 2 -m 1024 -bios bl1.bin   \
        -d unimp -semihosting-config enable,target=native

Booting via flash based firmware
--------------------------------

An alternate approach to deploy a full system stack on QEMU is to load the
firmware via a secure flash device.  This involves concatenating ``bl1.bin`` and
``fip.bin`` to create a boot ROM that is flashed onto secure FLASH0 with the
``-bios`` option.

For example, to test the following firmware stack:


-  BL32 - ``bl32.bin`` -> ``tee-header_v2.bin``
-  BL32 Extra1 - ``bl32_extra1.bin`` -> ``tee-pager_v2.bin``
-  BL32 Extra2 - ``bl32_extra2.bin`` -> ``tee-pageable_v2.bin``
-  BL33 - ``bl33.bin`` -> ``QEMU_EFI.fd`` (EDK II)
-  ``Image`` -> linux/arch/arm64/boot/Image


1.  Compile TF-A

  .. code:: shell

      make CROSS_COMPILE=aarch64-linux-gnu- PLAT=qemu BL32=bl32.bin \
          BL32_EXTRA1=bl32_extra1.bin BL32_EXTRA2=bl32_extra2.bin \
          BL33=bl33.bin BL32_RAM_LOCATION=tdram SPD=opteed all fip

  Or, alternatively, to build with TBBR enabled, as well as, BL31 and BL32 encrypted with
  test key:

  .. code:: shell

      make CROSS_COMPILE=aarch64-linux-gnu- PLAT=qemu BL32=bl32.bin \
          BL32_EXTRA1=bl32_extra1.bin BL32_EXTRA2=bl32_extra2.bin \
          BL33=bl33.bin BL32_RAM_LOCATION=tdram SPD=opteed all fip \
          MBEDTLS_DIR=<path-to-mbedtls-repo> TRUSTED_BOARD_BOOT=1 \
          GENERATE_COT=1 DECRYPTION_SUPPORT=aes_gcm FW_ENC_STATUS=0 \
          ENCRYPT_BL31=1 ENCRYPT_BL32=1

2.  Concatenate ``bl1.bin`` and ``fip.bin`` to create the boot ROM

  .. code:: shell

      dd if=build/qemu/release/bl1.bin of=flash.bin bs=4096 conv=notrunc
      dd if=build/qemu/release/fip.bin of=flash.bin seek=64 bs=4096 conv=notrunc

3.  Launch QEMU

  .. code:: shell

      qemu-system-aarch64 -nographic -machine virt,secure=on
          -cpu cortex-a57  -kernel Image   \
          -append 'console=ttyAMA0,38400 keep_bootcon'  \
          -initrd rootfs.cpio.gz -smp 2 -m 1024 -bios flash.bin   \
          -d unimp

The ``-bios`` option abstracts the loading of raw bare metal binaries into flash
or ROM memory. QEMU loads the binary into the region corresponding to
the hardware's entrypoint, from which the binary is executed upon a platform
"reset". In addition to this, it places the information about the kernel
provided with option ``-kernel``, and the RamDisk provided with ``-initrd``,
into the firmware configuration ``fw_cfg``. In this setup, EDK II is responsible
for extracting and launching these from ``fw_cfg``.

.. note::
    QEMU may be launched with or without ACPI (``-acpi``/``-no-acpi``). In
    either case, ensure that the kernel build options are aligned with the
    parameters passed to QEMU.

Running QEMU in OpenCI
-----------------------

Linaro's continuous integration platform OpenCI supports running emulated tests
on QEMU. The tests are kicked off on Jenkins and deployed through the Linaro
Automation and Validation Architecture `LAVA`_.

There are a set of Linux boot tests provided in OpenCI. They rely on prebuilt
`binaries`_ for UEFI, the kernel, root file system, as well as, any other TF-A
dependencies, and are run as part of the OpenCI TF-A `daily job`_. To run them
manually, a `builder`_ job may be triggered with the test configuration
``qemu-boot-tests``.


You may see the following warning repeated several times in the boot logs:

.. code:: shell

    pflash_write: Write to buffer emulation is flawed

Please ignore this as it is an unresolved `issue in QEMU`_, it is an internal
QEMU warning that logs flawed use of "write to buffer".

.. note::
    For more information on how to trigger jobs in OpenCI, please refer to
    Linaro's CI documentation, which explains how to trigger a `manual job`_.

.. _binaries: https://downloads.trustedfirmware.org/tf-a/linux_boot/
.. _daily job: https://ci.trustedfirmware.org/view/TF-A/job/tf-a-main/
.. _builder: https://ci.trustedfirmware.org/view/TF-A/job/tf-a-builder/
.. _LAVA: https://tf.validation.linaro.org/
.. _manual job: https://tf-ci-users-guide.readthedocs.io/en/latest/#manual-job-trigger
.. _issue in QEMU: https://git.qemu.org/?p=qemu.git;a=blob;f=hw/block/pflash_cfi01.c;h=0cbc2fb4cbf62c9a033b8dd89012374ff74ed610;hb=refs/heads/master#l500