[vbox-dev] Question regarding USB support under VirtualBOX

Hans Petter Selasky hselasky at c2i.net
Sun Jan 23 08:36:49 PST 2011


During usage of VirtualBOX under FreeBSD 8.2, I've noticed that the VM 
sometimes crashes if the USB string descriptors or other descriptors cannot be 
read or the device itself cannot be created, because the device is not 

From what I can understand VirtualBox USB enumeration has two stages:

1) Identifying devices
2) Probing devices

There is no guarantee that identified devices won't disappear until they are 
probed. Should the FreeBSD USB layer in this case return fake status values, 
to avoid VirtualBOX from asserting.

3) Reading any USB descriptor could theoretically fail at any time. The USB 
1/2 specification specifies the STALL message, and there can be bus errors 
aswell. Who is responsible for hiding these failures, so that the VirtualBOX 
machine does not assert()?


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