在ext4文件系统，虚拟机关于Host I/O cache的启动警告

The virtual machine execution may run into an error condition as described below. We suggest that you take an appropriate action to avert the error.

The host I/O cache for at least one controller is disabled and the medium'$HOME/VirtualBox VMs/Mac OS X/Mac OS X.vdi' for this VM is located on an ext4 partition. There is a known Linux kernel bug which can lead to the corruption of the virtual disk image under these conditions.

Either enable the host I/O cache permanently in the VM settings or put the disk image and the snapshot folder onto a different file system.

The host I/O cache will now be enabled for this medium.

解决方法：

Settings -> Storage -> SATA Controller -> 勾选Use Host I/O cache

警告就可以消除了。