# loongson3 virt generic platform (`virt`)

The `virt` machine use gpex host bridge, and there are some emulated devices on virt board, such as loongson7a RTC device, IOAPIC device, ACPI device and so on.

## Supported devices

The `virt` machine supports:

- Gpex host bridge

- Ls7a RTC device

- Ls7a IOAPIC device

- ACPI GED device

- Fw_cfg device

- PCI/PCIe devices

- Memory device

- CPU device. Type: la464.

## CPU and machine Type

The `qemu-system-loongarch64` provides emulation for virt machine. You can specify the machine type `virt` and cpu type `la464`.

## Boot options

We can boot the LoongArch virt machine by specifying the uefi bios, initrd, and linux kernel. And those source codes and binary files can be accessed by following steps.

1. Build qemu-system-loongarch64:

    ./configure --target-list="loongarch64-softmmu"
    make -j8

2. Set cross tools:

    wget https://github.com/loongson/build-tools/releases/download/2022.09.06/loongarch64-clfs-6.3-cross-tools-gcc-glibc.tar.xz
    tar -vxf loongarch64-clfs-6.3-cross-tools-gcc-glibc.tar.xz  -C /opt
    export PATH=/opt/cross-tools/bin:$PATH
    export LD_LIBRARY_PATH=/opt/cross-tools/lib:$LD_LIBRARY_PATH
    export LD_LIBRARY_PATH=/opt/cross-tools/loongarch64-unknown-linux-gnu/lib/:$LD_LIBRARY_PATH

Note: You need get the latest cross-tools at https://github.com/loongson/build-tools

3. Build BIOS:

   See: https://github.com/tianocore/edk2/tree/master/OvmfPkg/LoongArchVirt#readme

Note: To build the release version of the bios, set --buildtarget=RELEASE,

  the bios file path: Build/LoongArchQemu/RELEASE_GCC5/FV/QEMU_EFI.fd

4. Build kernel:

    git clone https://github.com/loongson/linux.git
    cd linux
    git checkout loongarch-next
    make ARCH=loongarch CROSS_COMPILE=loongarch64-unknown-linux-gnu- loongson3_defconfig
    make ARCH=loongarch CROSS_COMPILE=loongarch64-unknown-linux-gnu- -j32

Note: The branch of linux source code is loongarch-next.

  the kernel file: arch/loongarch/boot/vmlinuz.efi

5. Get initrd:

> You can use busybox tool and the linux modules to make a initrd file. Or you can access the binary files: https://github.com/yangxiaojuan-loongson/qemu-binary

    git clone https://github.com/yangxiaojuan-loongson/qemu-binary

Note: the initrd file is ramdisk

6. Booting LoongArch:

    $ ./build/qemu-system-loongarch64 -machine virt -m 4G -cpu la464 \
        -smp 1 -bios QEMU_EFI.fd -kernel vmlinuz.efi -initrd ramdisk \
        -serial stdio   -monitor telnet:localhost:4495,server,nowait \
        -append "root=/dev/ram rdinit=/sbin/init console=ttyS0,115200" \
        --nographic