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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
- No build instructions for QEMU\_EFI.fd and rootfs-arm64.cpio.gz
- No instructions for how to load a BL32 (Secure Payload)
``QEMU_EFI.fd`` can be dowloaded from
http://snapshots.linaro.org/components/kernel/leg-virt-tianocore-edk2-upstream/latest/QEMU-KERNEL-AARCH64/RELEASE_GCC5/QEMU_EFI.fd
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 v4.1.0):
.. code:: shell
qemu-system-aarch64 -nographic -machine virt,secure=on -cpu cortex-a57 \
-kernel Image \
-append "console=ttyAMA0,38400 keep_bootcon root=/dev/vda2" \
-initrd rootfs-arm64.cpio.gz -smp 2 -m 1024 -bios bl1.bin \
-d unimp -semihosting-config enable,target=native
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