无法从xrandr看到第二个虚拟监视器

我在OS X 10.11主机上运行Virtualbox 5.0.6上的Arch linux guest，并安装了最新的guest虚拟机添加件。我正在使用i3wm作为桌面。

我已经为我的VM添加了2个虚拟监视器，但在调用xrandr命令时只能看到其中一个。添加的客人是否与RandR或Xinerama兼容？

这xrandr是输出：

编辑

以下是与Virtualbox驱动程序相关的dmesg的摘录。我看不到任何加载错误。

[    3.925977] vboxguest: misc device minor 58, IRQ 20, I/O port d020, MMIO at 00000000f0400000 (size 0x400000)
[    3.925980] vboxguest: Successfully loaded version 5.0.6_OSE (interface 0x00010004)
[    3.926371] systemd[1]: Starting Load/Save Random Seed...
[    3.927860] systemd[1]: Starting Create Static Device Nodes in /dev...
[    3.929689] systemd[1]: Mounted Huge Pages File System.
[    3.949267] vboxsf: Successfully loaded version 5.0.6_OSE (interface 0x00010004)
[    3.960095] [drm] Initialized drm 1.1.0 20060810
[    3.961718] [drm] Initialized vboxvideo 1.0.0 20090303 for 0000:00:02.0 on minor 0

以下是与屏幕检测相关的Xorg.0.log摘录。最后三行有点令人不安，但他们说不在乎......

[  2129.737] (II) VBoxVideo(0): Creating default Display subsection in Screen section
        "Default Screen Section" for depth/fbbpp 24/32
[  2129.737] (==) VBoxVideo(0): Depth 24, (--) framebuffer bpp 32
[  2129.737] (--) VBoxVideo(0): Virtual size is 32766x32766 (pitch 32766)
[  2129.737] (**) VBoxVideo(0):  Built-in mode "800x600": 29.3 MHz (scaled from 0.0 MHz), 36.4 kHz, 60.0 Hz
[  2129.737] (II) VBoxVideo(0): Modeline "800x600"x0.0   29.31  800 802 804 806  600 602 604 606 (36.4 kHz b)
[  2129.737] (**) VBoxVideo(0):  Built-in mode "800x600": 29.3 MHz (scaled from 0.0 MHz), 36.4 kHz, 60.0 Hz
[  2129.737] (II) VBoxVideo(0): Modeline "800x600"x0.0   29.31  800 802 804 806  600 602 604 606 (36.4 kHz b)
[  2129.737] (II) VBoxVideo(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0
[  2129.737] (==) VBoxVideo(0): RGB weight 888
[  2129.737] (==) VBoxVideo(0): Default visual is TrueColor
[  2129.737] (==) VBoxVideo(0): Using gamma correction (1.0, 1.0, 1.0)
[  2129.737] (==) VBoxVideo(0): DPI set to (96, 96)
[  2129.737] (II) UnloadModule: "modesetting"
[  2129.737] (II) Unloading modesetting
[  2129.737] (--) Depth 24 pixmap format is 32 bpp
[  2129.830] (II) VBoxVideo(0): Requested monitor count: 1
[  2129.830] (II) VBoxVideo(0): Output VGA-0 using monitor section VGA-0
[  2129.830] (**) VBoxVideo(0): Option "PreferredMode" "1920x1080"
[  2129.830] (**) VBoxVideo(0): Option "Primary" "true"
[  2129.830] (II) VBoxVideo(0): Output VGA-0 using monitor section VGA-0
[  2129.830] (II) VBoxVideo(0): Printing probed modes for output VGA-0
[  2129.830] (II) VBoxVideo(0): Modeline "1920x1080"x60.0  125.50  1920 1922 1924 1926  1080 1082 1084 1086 (65.2 kHz U
Pb)
[  2129.830] (II) VBoxVideo(0): Modeline "800x600"x60.0   29.31  800 802 804 806  600 602 604 606 (36.4 kHz Pb)
[  2129.830] (II) VBoxVideo(0): Modeline "2560x1600"x60.0  247.26  2560 2562 2564 2566  1600 1602 1604 1606 (96.4 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "2560x1440"x60.0  222.63  2560 2562 2564 2566  1440 1442 1444 1446 (86.8 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "2048x1536"x60.0  190.04  2048 2050 2052 2054  1536 1538 1540 1542 (92.5 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1920x1600"x60.0  185.59  1920 1922 1924 1926  1600 1602 1604 1606 (96.4 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1600x1200"x60.0  116.21  1600 1602 1604 1606  1200 1202 1204 1206 (72.4 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1680x1050"x60.0  106.82  1680 1682 1684 1686  1050 1052 1054 1056 (63.4 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1400x1050"x60.0   89.08  1400 1402 1404 1406  1050 1052 1054 1056 (63.4 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1280x1024"x60.0   79.47  1280 1282 1284 1286  1024 1026 1028 1030 (61.8 kHz b
)
[  2129.830] (II) VBoxVideo(0): Modeline "1024x768"x60.0   47.83  1024 1026 1028 1030  768 770 772 774 (46.4 kHz b)
[  2129.830] (II) VBoxVideo(0): Modeline "800x600"x60.0   29.31  800 802 804 806  600 602 604 606 (36.4 kHz b)
[  2129.830] (II) VBoxVideo(0): Modeline "640x480"x60.0   18.84  640 642 644 646  480 482 484 486 (29.2 kHz b)
[  2129.830] (II) VBoxVideo(0): Output VGA-0 connected
[  2129.830] (II) VBoxVideo(0): Using user preference for initial modes
[  2129.830] (II) VBoxVideo(0): Output VGA-0 using initial mode 1920x1080
[  2129.830] (II) VBoxVideo(0): Using default gamma of (1.0, 1.0, 1.0) unless otherwise stated.
[  2129.830] (II) VBoxVideo(0): RandR 1.2 enabled, ignore the following RandR disabled message.
[  2129.831] (==) VBoxVideo(0): DPMS enabled
[  2129.831] (--) RandR disabled