# 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)

- XRAM (4MB of on chip Accelerator RAM)

- DDR memory

- BBRAM (36 bytes of Battery-backed RAM)

- eFUSE (3072 bytes of one-time field-programmable bit array)

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

## BBRAM File Backend

BBRAM can have an optional file backend, which must be a seekable binary file with a size of 36 bytes or larger. A file with all binary 0s is a ‘blank’.

To add a file-backend for the BBRAM:

    -drive if=pflash,index=0,file=versal-bbram.bin,format=raw

To use a different index value, N, from default of 0, add:

    -global xlnx,bbram-ctrl.drive-index=N

## eFUSE File Backend

eFUSE can have an optional file backend, which must be a seekable binary file with a size of 3072 bytes or larger. A file with all binary 0s is a ‘blank’.

To add a file-backend for the eFUSE:

    -drive if=pflash,index=1,file=versal-efuse.bin,format=raw

To use a different index value, N, from default of 1, add:

    -global xlnx,efuse.drive-index=N

Warning

In actual physical Versal, BBRAM and eFUSE contain sensitive data. The QEMU device models do not encrypt nor obfuscate any data when holding them in models’ memory or when writing them to their file backends.

Thus, a file backend should be used with caution, and ‘format=luks’ is highly recommended (albeit with usage complexity).

Better yet, do not use actual product data when running guest image on this Xilinx Versal Virt board.