### Qemu RISC-V virt HOWTO

#### 1. Brief introduction
`riscv32_virt/` subdirectory contains part of the OpenHarmony LiteOS demonstration support for Qemu risc-v virt Platform,
here called *riscv32_virt*.
RISC-V Virtual platform is a `qemu-system-riscv32` machine target that provides emulation
for a generic, riscv-based board.

Introduced functionality adds support for RISC-V (1 CPU with security extensions), 128MB memory virtual platform.

Note: System memory size is hard-coded to 128MB.

#### 2. Setting up environment

[Setting up a development environment](https://gitee.com/openharmony/docs/blob/HEAD/en/device-dev/quick-start/quickstart-lite-env-setup.md)

[Compiler install:gcc_riscv32](https://gitee.com/openharmony/docs/blob/HEAD/en/device-dev/quick-start/quickstart-lite-steps-hi3861-setting.md#section34435451256),
Note: [Downloadable directly](https://repo.huaweicloud.com/harmonyos/compiler/gcc_riscv32/7.3.0/linux/gcc_riscv32-linux-7.3.0.tar.gz)

#### 3. Code acquisition

[Code acquisition](https://gitee.com/openharmony/docs/blob/HEAD/en/device-dev/get-code/sourcecode-acquire.md)

Note: One can use `repo` to fetch code in a straightforward manner.

#### 4. Building from sources

In the root directory of the obtained source code, run the following command:

```
hb set
```

Select `qemu_riscv_mini_system_demo` under **ohemu**.

Run the following build command:

```
hb build
```

This will build `OHOS_Image` for Qemu RISC-V virt machine.

After build is finished, the resulting image can be found in:
```
out/riscv32_virt/qemu_riscv_mini_system_demo/
```

#### 5. Running image in Qemu

a) If not installed, please install `qemu-system-riscv32`
For details, please refer to the HOWTO: [Qemu installation](https://gitee.com/openharmony/device_qemu/blob/HEAD/README.md)

b) Run

(1) qemu version < 5.0.0

```
cd device/qemu/riscv32_virt
qemu-system-riscv32 -machine virt -m 128M -kernel ../../../out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image -nographic -append "root=dev/vda or console=ttyS0"
```

(2). qemu version >= 5.0.0

Run the `./qemu-run --help` command. The following information is displayed:

```
Usage: ./qemu-run [OPTION]...
Run a OHOS image in qemu according to the options.

    Options:

    -e, --exec file_name     kernel exec file name
    -n, --net-enable         enable net
    -l, --local-desktop      no VNC
    -g, --gdb                enable gdb for kernel
    -t, --test               test mode, exclusive with -g
    -h, --help               print help info

    By default, the kernel exec file is: out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image,
    and net will not be enabled, gpu enabled and waiting for VNC connection at port 5920.
```
By default, the network will not be automatically configured if no parameter is specified, and the default kernel exec file will be used.
If you want to use other kernel exec file, please try `./qemu-run -e [file_name]` to change it.

#### 6. gdb debug

```
cd device/qemu/riscv32_virt
vim liteos_m/config.gni
```

In the modified `board_opt_flags` compiler options:

```
board_opt_flags = []
```

to:

```
board_opt_flags = [ "-g" ]
```

Save and exit, recompile under OHOS root directory:

```
hb build -f
```

In a window to enter the command:

```
./qemu-run -g
```

In another window to enter the command:

```
riscv32-unknown-elf-gdb out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image
(gdb) target remote localhost:1234
(gdb) b main
```

More GDB related debugging can refer to [GDB instruction manual](https://sourceware.org/gdb/current/onlinedocs/gdb).

## 7. Example

- [Transferring Files Using FAT Images](example.md#sectionfatfs)

# Qemu RISC-V virt 教程

## 1. 简介
`riscv32_virt/` 子目录包含部分Qemu RISC-V虚拟化平台验证的OpenHarmony kernel\_liteos\_m的代码，目录名为*riscv32_virt*。
RISC-V 虚拟化平台是一个 `qemu-system-riscv32` 的目标设备，通过它来模拟一个通用的、基于RISC-V架构的单板。

这次模拟的配置是：RISC-V架构，1个CPU，128M内存。

提示: 系统内存硬编码为128MB。

## 2. 环境搭建

[环境搭建](https://gitee.com/openharmony/docs/blob/HEAD/zh-cn/device-dev/quick-start/quickstart-lite-env-setup.md)

[编译器安装:gcc_riscv32](https://gitee.com/openharmony/docs/blob/HEAD/zh-cn/device-dev/quick-start/quickstart-lite-steps-hi3861-setting.md#section34435451256),
提示: [可直接下载](https://repo.huaweicloud.com/harmonyos/compiler/gcc_riscv32/7.3.0/linux/gcc_riscv32-linux-7.3.0.tar.gz)

## 3. 获取源码

[代码获取](https://gitee.com/openharmony/docs/blob/HEAD/zh-cn/device-dev/get-code/sourcecode-acquire.md)

提示: 可以使用 `repo` 命令来获取源码。

## 4. 源码构建

在已经获取的源码根目录，请输入：

```
hb set
```

选择ohemu下的`qemu_riscv_mini_system_demo`选项。


然后执行构建命令如下：

```
hb build
```

这个命令构建会产生 `OHOS_Image` 的镜像文件。

在构建完成之后，对应的镜像文件在如下目录：
```
out/riscv32_virt/qemu_riscv_mini_system_demo/
```

## 5. 在Qemu中运行镜像

a) 如果没有安装 `qemu-system-riscv32` ，安装请参考链接:[Qemu安装指导](https://gitee.com/openharmony/device_qemu/blob/HEAD/README_zh.md)

b) 运行

(1). qemu 版本 < 5.0.0

```
cd device/qemu/riscv32_virt
qemu-system-riscv32 -machine virt -m 128M -kernel ../../../out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image -nographic -append "root=dev/vda or console=ttyS0"
```

(2). qemu 版本 >= 5.0.0

执行`./qemu-run --help`提示如下：

```
Usage: qemu-run [OPTION]...
Run a OHOS image in qemu according to the options.

    Options:

    -e, --exec file_name     kernel exec file name
    -n, --net-enable         enable net
    -l, --local-desktop      no VNC
    -g, --gdb                enable gdb for kernel
    -t, --test               test mode, exclusive with -g
    -h, --help               print help info

    By default, the kernel exec file is: out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image,
    and net will not be enabled, gpu enabled and waiting for VNC connection at port 5920.
```
默认不加参数的情况下，网络不会自动配置，并使用默认镜像文件，若需更改默认镜像文件，可以利用 `./qemu-run -e [file_name]` 指定

## 6. gdb调试

```
cd device/qemu/riscv32_virt
vim liteos_m/config.gni
```

将 `board_opt_flags` 中的

```
board_opt_flags = []
```

编译选项修改为:

```
board_opt_flags = [ "-g" ]
```

保存并退出，在OHOS根目录重新编译:

```
hb build -f
```

在一个窗口中输入命令：

```
./qemu-run -g
```

在另一个窗口中输入命令：

```
riscv32-unknown-elf-gdb out/riscv32_virt/qemu_riscv_mini_system_demo/OHOS_Image
(gdb) target remote localhost:1234
(gdb) b main
```

更多gdb相关的调试可以查阅：[gdb指导手册](https://sourceware.org/gdb/current/onlinedocs/gdb)。

## 7. 用法示例

- [用FAT映像传递文件](example.md#sectionfatfs)