# Xilinx Versal Virt (`xlnx-versal-virt`)

Xilinx Versal is a family of heterogeneous multi-core SoCs (System on Chip) that combine traditional hardened CPUs and I/O peripherals in a Processing System (PS) with runtime programmable FPGA logic (PL) and an Artificial Intelligence Engine (AIE).

More details here: https://www.xilinx.com/products/silicon-devices/acap/versal.html

The family of Versal SoCs share a single architecture but come in different parts with different speed grades, amounts of PL and other differences.

The Xilinx Versal Virt board in QEMU is a model of a virtual board (does not exist in reality) with a virtual Versal SoC without I/O limitations. Currently, we support the following cores and devices:

Implemented CPU cores:

- 2 ACPUs (ARM Cortex-A72)

Implemented devices:

- Interrupt controller (ARM GICv3)

- 2 UARTs (ARM PL011)

- An RTC (Versal built-in)

- 2 GEMs (Cadence MACB Ethernet MACs)

- 8 ADMA (Xilinx zDMA) channels

- 2 SD Controllers

- OCM (256KB of On Chip Memory)

- DDR memory

QEMU does not yet model any other devices, including the PL and the AI Engine.

Other differences between the hardware and the QEMU model:

- QEMU allows the amount of DDR memory provided to be specified with the `-m` argument. If a DTB is provided on the command line then QEMU will edit it to include suitable entries describing the Versal DDR memory ranges.

- QEMU provides 8 virtio-mmio virtio transports; these start at address `0xa0000000` and have IRQs from 111 and upwards.

## Running

If the user provides an Operating System to be loaded, we expect users to use the `-kernel` command line option.

Users can load firmware or boot-loaders with the `-device loader` options.

When loading an OS, QEMU generates a DTB and selects an appropriate address where it gets loaded. This DTB will be passed to the kernel in register x0.

If there’s no `-kernel` option, we generate a DTB and place it at 0x1000 for boot-loaders or firmware to pick it up.

If users want to provide their own DTB, they can use the `-dtb` option. These DTBs will have their memory nodes modified to match QEMU’s selected ram_size option before they get passed to the kernel or FW.

When loading an OS, we turn on QEMU’s PSCI implementation with SMC as the PSCI conduit. When there’s no `-kernel` option, we assume the user provides EL3 firmware to handle PSCI.

A few examples:

Direct Linux boot of a generic ARM64 upstream Linux kernel:

    $ qemu-system-aarch64 -M xlnx-versal-virt -m 2G \
        -serial mon:stdio -display none \
        -kernel arch/arm64/boot/Image \
        -nic user -nic user \
        -device virtio-rng-device,bus=virtio-mmio-bus.0 \
        -drive if=none,index=0,file=hd0.qcow2,id=hd0,snapshot \
        -drive file=qemu_sd.qcow2,if=sd,index=0,snapshot \
        -device virtio-blk-device,drive=hd0 -append root=/dev/vda

Direct Linux boot of PetaLinux 2019.2:

    $ qemu-system-aarch64  -M xlnx-versal-virt -m 2G \
        -serial mon:stdio -display none \
        -kernel petalinux-v2019.2/Image \
        -append "rdinit=/sbin/init console=ttyAMA0,115200n8 earlycon=pl011,mmio,0xFF000000,115200n8" \
        -net nic,model=cadence_gem,netdev=net0 -netdev user,id=net0 \
        -device virtio-rng-device,bus=virtio-mmio-bus.0,rng=rng0 \
        -object rng-random,filename=/dev/urandom,id=rng0

Boot PetaLinux 2019.2 via ARM Trusted Firmware (2018.3 because the 2019.2 version of ATF tries to configure the CCI which we don’t model) and U-boot:

    $ qemu-system-aarch64 -M xlnx-versal-virt -m 2G \
        -serial stdio -display none \
        -device loader,file=petalinux-v2018.3/bl31.elf,cpu-num=0 \
        -device loader,file=petalinux-v2019.2/u-boot.elf \
        -device loader,addr=0x20000000,file=petalinux-v2019.2/Image \
        -nic user -nic user \
        -device virtio-rng-device,bus=virtio-mmio-bus.0,rng=rng0 \
        -object rng-random,filename=/dev/urandom,id=rng0

Run the following at the U-Boot prompt:

    Versal>
    fdt addr $fdtcontroladdr
    fdt move $fdtcontroladdr 0x40000000
    fdt set /timer clock-frequency <0x3dfd240>
    setenv bootargs "rdinit=/sbin/init maxcpus=1 console=ttyAMA0,115200n8 earlycon=pl011,mmio,0xFF000000,115200n8"
    booti 20000000 - 40000000
    fdt addr $fdtcontroladdr

Boot Linux as DOM0 on Xen via U-Boot:

    $ qemu-system-aarch64 -M xlnx-versal-virt -m 4G \
        -serial stdio -display none \
        -device loader,file=petalinux-v2019.2/u-boot.elf,cpu-num=0 \
        -device loader,addr=0x30000000,file=linux/2018-04-24/xen \
        -device loader,addr=0x40000000,file=petalinux-v2019.2/Image \
        -nic user -nic user \
        -device virtio-rng-device,bus=virtio-mmio-bus.0,rng=rng0 \
        -object rng-random,filename=/dev/urandom,id=rng0

Run the following at the U-Boot prompt:

    Versal>
    fdt addr $fdtcontroladdr
    fdt move $fdtcontroladdr 0x20000000
    fdt set /timer clock-frequency <0x3dfd240>
    fdt set /chosen xen,xen-bootargs "console=dtuart dtuart=/uart@ff000000 dom0_mem=640M bootscrub=0 maxcpus=1 timer_slop=0"
    fdt set /chosen xen,dom0-bootargs "rdinit=/sbin/init clk_ignore_unused console=hvc0 maxcpus=1"
    fdt mknode /chosen dom0
    fdt set /chosen/dom0 compatible "xen,multiboot-module"
    fdt set /chosen/dom0 reg <0x00000000 0x40000000 0x0 0x03100000>
    booti 30000000 - 20000000

Boot Linux as Dom0 on Xen via ARM Trusted Firmware and U-Boot:

    $ qemu-system-aarch64 -M xlnx-versal-virt -m 4G \
        -serial stdio -display none \
        -device loader,file=petalinux-v2018.3/bl31.elf,cpu-num=0 \
        -device loader,file=petalinux-v2019.2/u-boot.elf \
        -device loader,addr=0x30000000,file=linux/2018-04-24/xen \
        -device loader,addr=0x40000000,file=petalinux-v2019.2/Image \
        -nic user -nic user \
        -device virtio-rng-device,bus=virtio-mmio-bus.0,rng=rng0 \
        -object rng-random,filename=/dev/urandom,id=rng0

Run the following at the U-Boot prompt:

    Versal>
    fdt addr $fdtcontroladdr
    fdt move $fdtcontroladdr 0x20000000
    fdt set /timer clock-frequency <0x3dfd240>
    fdt set /chosen xen,xen-bootargs "console=dtuart dtuart=/uart@ff000000 dom0_mem=640M bootscrub=0 maxcpus=1 timer_slop=0"
    fdt set /chosen xen,dom0-bootargs "rdinit=/sbin/init clk_ignore_unused console=hvc0 maxcpus=1"
    fdt mknode /chosen dom0
    fdt set /chosen/dom0 compatible "xen,multiboot-module"
    fdt set /chosen/dom0 reg <0x00000000 0x40000000 0x0 0x03100000>
    booti 30000000 - 20000000