1QEMU virt Armv8-A 2================= 3 4Trusted Firmware-A (TF-A) implements the EL3 firmware layer for QEMU virt 5Armv8-A. BL1 is used as the BootROM, supplied with the -bios argument. 6When QEMU starts all CPUs are released simultaneously, BL1 selects a 7primary CPU to handle the boot and the secondaries are placed in a polling 8loop to be released by normal world via PSCI. 9 10BL2 edits the Flattened Device Tree, FDT, generated by QEMU at run-time to 11add a node describing PSCI and also enable methods for the CPUs. 12 13If ``ARM_LINUX_KERNEL_AS_BL33`` is set to 1 then this FDT will be passed to BL33 14via register x0, as expected by a Linux kernel. This allows a Linux kernel image 15to be booted directly as BL33 rather than using a bootloader. 16 17An ARM64 defconfig v5.5 Linux kernel is known to boot, FDT doesn't need to be 18provided as it's generated by QEMU. 19 20Current limitations: 21 22- Only cold boot is supported 23- No build instructions for QEMU\_EFI.fd and rootfs-arm64.cpio.gz 24- No instructions for how to load a BL32 (Secure Payload) 25 26``QEMU_EFI.fd`` can be dowloaded from 27http://snapshots.linaro.org/components/kernel/leg-virt-tianocore-edk2-upstream/latest/QEMU-KERNEL-AARCH64/RELEASE_GCC5/QEMU_EFI.fd 28 29Boot binaries, except BL1, are primarily loaded via semi-hosting so all 30binaries has to reside in the same directory as QEMU is started from. This 31is conveniently achieved with symlinks the local names as: 32 33- ``bl2.bin`` -> BL2 34- ``bl31.bin`` -> BL31 35- ``bl33.bin`` -> BL33 (``QEMU_EFI.fd``) 36- ``Image`` -> linux/arch/arm64/boot/Image 37 38To build: 39 40.. code:: shell 41 42 make CROSS_COMPILE=aarch64-none-elf- PLAT=qemu 43 44To start (QEMU v4.1.0): 45 46.. code:: shell 47 48 qemu-system-aarch64 -nographic -machine virt,secure=on -cpu cortex-a57 \ 49 -kernel Image \ 50 -append "console=ttyAMA0,38400 keep_bootcon root=/dev/vda2" \ 51 -initrd rootfs-arm64.cpio.gz -smp 2 -m 1024 -bios bl1.bin \ 52 -d unimp -semihosting-config enable,target=native 53