# KVM虚拟机vnc远程访问鼠标偏移修复

在使用KVM运行的虚拟机，当VNC客户端连接服务器，例如Windows桌面，会发现实际鼠标移动和桌面上的鼠标移动不协调，且有偏移。

解决的方法是在启动guest的时候，qemu加上参数`-usb –usbdevice tablet`，例如：

```
qemu-kvm -smp 4 -m 2048 -hda /images/Win7.img -usb -usbdevice tablet
```

这个方法在Xen和KVM中都是通用的。

在Xen启动guest，配置中添加如下两行：

```
usb=1 
usbdevice='tablet'
```

如果是采用libvirtd启动虚拟机，在虚拟机的xml配置的`<input type='mouse' bus='ps2'/>`项前面中添加如下配置：

```markup
    <input type='tablet' bus='usb'>
        <alias name='input0'/>
    </input>
    <input type='mouse' bus='ps2'/>
```

然后重新启动虚拟机（不需要destroy，只需要shutdown然后start），在终端中检查qemu进程，可以看到参数如下：

```
/usr/bin/qemu-kvm -name win2016 -kvmdev /dev/kvm0 -S -machine pc-i440fx-2.1,accel=kvm,usb=off ... -device usb-tablet,id=input0 ...
```

## 参考

* [Xen/KVM中解决鼠标移动问题](http://smilejay.com/2012/06/xen-kvm-cursor-movement/)
* [VNCViewer连接KVM虚机鼠标不同步问题](https://blog.csdn.net/submorino/article/details/40982807)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://huataihuang.gitbook.io/cloud-atlas-draft/virtual/kvm/startup/in_action/kvm_vnc_mouse.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.