When I've used virtual machines, they emulate or virtualize one or two common sound cards. To the guest OS, the virtual machine's emulated sound card looks like an *actual* sound card. So the guest OS uses a driver for the emulated sound card, not the actual hardware on the real computer. As far as the guest OS is concerned, the virtual hardware IS the actual hardware. The virtual machine software takes care of translating between the virtual sound card in the virtual machine and the actual sound card in the physical computer. The Alsa driver in the guest OS should be the one for the virtualized sound card, not the sound used by the host OS.
Maybe we're all saying the same thing.