Cannot get sound in Qemu/KVM vm

[Unknown]

Hello. I have a Parabola linux x64 host and a Parabola Linux 32-bit
guest. Parabola is an Arch-based distro. I also have a Windows 7 x64
guest that lacks audio. 

lspci in the
host tells me that I have an Intel 100 Series/C230 Series Chipset
Family HD Audio Controller and an NVIDIA GM107 High Def Audio
Controller.

The host always has sound. The guest used to have sound, but I'd
continually lose sound after a few days until I restarted the VM. Then
the guest lost sound completely; I don't know why. Media players,
youtube videos, etc. seem to play normally, but I simply cannot hear
anything, with or without headphones. Alsa and pulseaudio are installed
in the guest.

I've tried setting QEMU_AUDIO_DRV (to alsa) on the host. I've tried
all of the sound device settings in libvirt (ICH6, ICH9, and AC97).
I've tried deleting pulseaudio from the guest. I've tried maxing out the
volume on both the guest (with alsamixer and pavucontrol) and the host
(with alsamixer).

Any suggestions? I have read that audio is some sort of ongoing problem
with KVM. Is this true?