Couldn't mine bitcoins in the VM

I finally got around to trying to mine bitcoins using the Radeon HD 7870 GHz Edition that is VGA-Passthroughed to a Windows 7 VM.  I couldn't get Miner-src to use the GPU.  It did offer to use the CPU, but I didn't bother trying to get that to work.  I should try it out and see what the Xen CPU mining overhead is, but I haven't.  It would be nice to get the 7870 to GPU mine, but its not that important to me.