1# QEMU Arm Virt Tutorial - liteos_a 2 3## 1. Overview 4 5The `arm_virt/` directory contains code that has been verified on the QEMU Arm Virt platform for adapting to OpenHarmony kernel\_liteos\_a. The code includes the driver and board configurations. 6 7The Arm Virt platform is a `qemu-system-arm` target device that simulates a general-purpose board running on the Arm architecture. 8The board whose **machine** is **virt** in QEMU is configurable. For example, you can select the core type and quantity, memory size, and security extensions when configuring the board. 9 10This tutorial guides you through the configuration of a board based on the Cortex-A7 architecture, with one CPU, extended secure features, Generic Interrupt Controller versions 2 (GICv2), and 1 GB memory. 11The system memory is hardcoded to 64 MB. 12 13## 2. Setting Up the Environment 14 15For details, see [Environment Setup](https://gitee.com/openharmony/docs/blob/master/en/device-dev/quick-start/Readme-EN.md). 16 17## 3. Obtaining the Source Code 18 19For details, see [Source Code Acquisition](https://gitee.com/openharmony/docs/blob/HEAD/en/device-dev/get-code/sourcecode-acquire.md). 20 21## 4. Building the Source Code 22 23In the root directory of the obtained source code, run the following command: 24 25``` 26hb set 27``` 28 29Select `qemu_small_system_demo` under **ohemu**. 30 31Run the following build command: 32 33``` 34hb build 35``` 36 37After this command is executed, the result files are generated in out/arm_virt/qemu_small_system_demo/ directory. 38 39## 5. Running an Image in QEMU 40 41a) If `qemu-system-arm` has not been installed, install it. For details, see [Qemu Installation](https://gitee.com/openharmony/device_qemu/blob/HEAD/README.md). 42 43Note: The introduced functions have been tested on the target machine of virt-5.1, but are not available for all QEMU versions. Therefore, you must ensure that the qemu-system-arm version is 5.1 or later. 44 45b) Create and run an image. 46 47After the source code is built, the **qemu-run** script is generated in the root directory of the code. You can run the script to create and run an image as prompted. 48 49Run `./qemu-run --help` to get help. 50 51Simulated network interface is wireless card wlan0, but has no real wifi functions. By default, the network will not be automatically configured if no parameter is specified. 52 53If the image file **out/smallmmc.img** exists, the image will not be re-created by default. MMC image mainly for rootfs and userfs. The 1st partition is rootfs, 2nd is userfs and mounted at /userdata, 3rd is for user data and mounted at /userdata. 54 55c) Exit QEMU. 56 57Press `Ctrl-A + x` to exit the QEMU virtual environment. 58 59## 6. gdb debug 60 61Install `gdb-multiarch` package: 62``` 63sudo apt install gdb-multiarch 64``` 65Then, 66``` 67cd ohos/vendor/ohemu/qemu_small_system_demo/kernel_configs 68vim debug.config 69``` 70 71Modify `LOSCFG_CC_STACKPROTECTOR_ALL=y` to: 72 73``` 74# LOSCFG_CC_STACKPROTECTOR_ALL is not set 75LOSCFG_COMPILE_DEBUG=y 76``` 77 78Save and exit, recompile under OHOS root directory: 79 80``` 81hb build -f 82``` 83 84In a window to enter the command: 85 86``` 87./qemu-run -g 88``` 89 90In another window to enter the command: 91 92``` 93gdb-multiarch out/arm_virt/qemu_small_system_demo/OHOS_Image 94(gdb) target remote localhost:1234 95``` 96 97More GDB related debugging can refer to [GDB instruction manual](https://sourceware.org/gdb/current/onlinedocs/gdb). 98 99## 7. Example 100 101- [Transferring Parameters to the Kernel](example.md#sectiondebug) 102 103- [Transferring Files Using MMC Images](example.md#sectionfatfs) 104 105- [Adding a Hello World Program](example.md#addhelloworld) 106 107- [Running the Graphic Demo](example.md#simple_ui_demo) 108 109- [Observe dsoftbus Discovery](example.md#dsoftbus_discover) 110 111- [Hack A Sample Desktop](example.md#desktop) 112 113## FAQ: 1141. How do I locate a network configuration problem? 115 116 Manually configure a host network bridge. For Linux, run the following commands: 117 118 ``` 119 sudo modprobe tun tap 120 sudo ip link add br0 type bridge 121 sudo ip address add 10.0.2.2/24 dev br0 122 sudo ip link set dev br0 up 123 124 # The following commands can be commented out after being executed: 125 sudo mkdir -p /etc/qemu 126 echo 'allow br0' | sudo tee -a /etc/qemu/bridge.conf 127 ``` 128 129 Run the **ip addr** command to check the configuration. If **br0** does not exist or the value in the angle brackets is **DOWN**, check the configuration commands again. 130 131 ``` 132 5: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 133 link/ether 2e:52:52:0e:21:44 brd ff:ff:ff:ff:ff:ff 134 inet 10.0.2.2/24 scope global br0 135 valid_lft forever preferred_lft forever 136 ``` 137 138 If software such as Docker has been installed in the system, the system firewall may prevent the bridge from accessing the system. Run the following command: 139 140 `cat /proc/sys/net/bridge/bridge-nf-call-iptables` 141 142 **1** is displayed. Run the following command to allow the access from the network bridge: 143 144 ``` 145 echo 0 | sudo tee /proc/sys/net/bridge/bridge-nf-call-iptables 146 ``` 147 148 Note: The system is hardcoded to **10.0.2.0/24** for the sub-network, **10.0.2.2** for the gateway, and random IP address. Use different MAC addresses, IP addresses, and flash, MMC images for different client instances. The MAC address can be transferred using the QEMU command line. The IP address can be adjusted in the OHOS command line, for example, using `ifconfig wlan0 inet 10.0.2.30` or other methods. 149 1502. How do I troubleshoot the error when running `qemu-system-arm`? 151 152 The commands and parameters in the **qemu-run** script are as follows: 153 154 ``` 155 qemu-system-arm -M virt,gic-version=2,secure=on -cpu cortex-a7 -smp cpus=1 -m 1G \ 156 -bios out/arm_virt/qemu_small_system_demo/OHOS_Image.bin \ 157 -drive if=none,file=out/smallmmc.img,format=raw,id=mmc 158 -device virtio-blk-device,drive=mmc \ 159 -netdev bridge,id=net0 \ 160 -device virtio-net-device,netdev=net0,mac=12:22:33:44:55:66 \ 161 -device virtio-gpu-device,xres=960,yres=480 \ 162 -device virtio-tablet-device \ 163 -device virtio-rng-device \ 164 -vnc :20 \ 165 -s -S \ 166 -global virtio-mmio.force-legacy=false 167 ``` 168 169 ``` 170 -M Virtual machine type, ARM virt, GICv2, and extended security features 171 -cpu CPU model 172 -smp SMP setting, single core 173 -m Maximum memory size that can be used by the virtual machines 174 -drive if=none Block device image setting 175 -netdev [optional] NIC bridge type 176 -device virtio-blk-device Block device 177 -device virtio-net-device [optional] NIC device 178 -device virtio-gpu-device GPU device 179 -device virtio-tablet-device Input device 180 -device virtio-rng-device Random generator device 181 -vnc: 20 [recommend] Remote desktop connection, port 5920 182 -s -S [optional] gdb single step debug 183 -global QEMU configuration parameter, which cannot be changed 184 ``` 185 186 If the error message "failed to parse default acl file" is displayed when **qemu-run** is executed: 187 188 The error may be caused by the QEMU configuration file path, which varies with the QEMU installation mode. The default QEMU configuration file path is: 189 190 - **/usr/local/qemu/etc/qemu** if QEMU is installed from the source code. 191 192 - **/ect/qemu/** if QEMU is installed by using a Linux distribution installation tool. 193 194 Determine the configuration file path and run the following command: 195 196 ``` 197 echo 'allow br0' | sudo tee -a <Configuration file path> 198 ``` 199 200 2013. What do I do if there is no output after QEMU of LTS 1.1.0 is executed? 202 203 The LTS code has a kernel startup defect. You can try to resolve the problem by referring to the following: 204 205 https://gitee.com/openharmony/kernel_liteos_a/pulls/324 206 207 2084. VNC window has no cursor? 209 210 Virtio-tablet is an emulated tablet input device. Neither QEMU captures nor the virtual machine displays it. The cursor is displayed by VNC client. Please check VNC client options.