I have a Windows 10 Pro virtual machine using KVM. It is set up through virt-manager using the latest version of libvirt and QEMU. All of this is running on Manjaro Linux 20. Manjaro defaults to using PulseAudio for its audio output (at least for Manjaro 20). I was wondering if there is a way to use PulseAudio with libvirt/QEMU/KVM to have an audio pass-through from the guest OS to the host. Meaning that anything that is playing in the Guest OS will need to be heard through the default output device in Manjaro Linux. First, I tried setting environment variables to set it up, but that didn't work, and it also is deprecated past QEMU 4.1 (I am using 5.1.) Then, I tried using this tutorial, which ended up somehow bricking Manjaro, and I had to reinstall. I am currently using the default Spice server through virt-manager. I have heard that the Spice server introduces lots of overhead, and I can't afford that. I need every CPU cycle, and if PulseAudio is already running, I may as well use it. My libvirt XML config WITHOUT the Spice server is as follows:
<domain type="kvm">
<name>windows10pro</name>
<uuid>1916e748-a979-40b7-b9d3-ff1b9a16155e</uuid>
<metadata>
<libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
<libosinfo:os id="http://microsoft.com/win/10"/>
</libosinfo:libosinfo>
</metadata>
<memory unit="KiB">16777216</memory>
<currentMemory unit="KiB">16777216</currentMemory>
<vcpu placement="static">4</vcpu>
<os>
<type arch="x86_64" machine="pc-q35-5.1">hvm</type>
<loader readonly="yes" type="pflash">/usr/share/edk2-ovmf/x64/OVMF_CODE.fd</loader>
<nvram>/var/lib/libvirt/qemu/nvram/windows10pro_VARS.fd</nvram>
<boot dev="hd"/>
</os>
<features>
<acpi/>
<apic/>
<hyperv>
<relaxed state="on"/>
<vapic state="on"/>
<spinlocks state="on" retries="8191"/>
<vendor_id state="on" value="none"/>
</hyperv>
<kvm>
<hidden state="on"/>
</kvm>
<vmport state="off"/>
</features>
<cpu mode="host-passthrough" check="partial" migratable="on">
<topology sockets="1" dies="1" cores="4" threads="1"/>
<feature policy="disable" name="hypervisor"/>
</cpu>
<clock offset="localtime">
<timer name="rtc" tickpolicy="catchup"/>
<timer name="pit" tickpolicy="delay"/>
<timer name="hpet" present="no"/>
<timer name="hypervclock" present="yes"/>
</clock>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<pm>
<suspend-to-mem enabled="no"/>
<suspend-to-disk enabled="no"/>
</pm>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<disk type="file" device="disk">
<driver name="qemu" type="qcow2"/>
<source file="/var/lib/libvirt/images/windows10pro.qcow2"/>
<target dev="vda" bus="virtio"/>
<address type="pci" domain="0x0000" bus="0x04" slot="0x00" function="0x0"/>
</disk>
<controller type="usb" index="0" model="qemu-xhci" ports="15">
<address type="pci" domain="0x0000" bus="0x02" slot="0x00" function="0x0"/>
</controller>
<controller type="sata" index="0">
<address type="pci" domain="0x0000" bus="0x00" slot="0x1f" function="0x2"/>
</controller>
<controller type="pci" index="0" model="pcie-root"/>
<controller type="pci" index="1" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="1" port="0x10"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0" multifunction="on"/>
</controller>
<controller type="pci" index="2" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="2" port="0x11"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x1"/>
</controller>
<controller type="pci" index="3" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="3" port="0x12"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x2"/>
</controller>
<controller type="pci" index="4" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="4" port="0x13"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x3"/>
</controller>
<controller type="pci" index="5" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="5" port="0x14"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x4"/>
</controller>
<controller type="pci" index="6" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="6" port="0x15"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x5"/>
</controller>
<controller type="pci" index="7" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="7" port="0x8"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x0" multifunction="on"/>
</controller>
<controller type="pci" index="8" model="pcie-root-port">
<model name="pcie-root-port"/>
<target chassis="8" port="0x9"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x1"/>
</controller>
<controller type="pci" index="9" model="pcie-to-pci-bridge">
<model name="pcie-pci-bridge"/>
<address type="pci" domain="0x0000" bus="0x08" slot="0x00" function="0x0"/>
</controller>
<controller type="virtio-serial" index="0">
<address type="pci" domain="0x0000" bus="0x03" slot="0x00" function="0x0"/>
</controller>
<interface type="network">
<mac address="52:54:00:fe:e2:a2"/>
<source network="default"/>
<model type="e1000e"/>
<address type="pci" domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
</interface>
<input type="tablet" bus="usb">
<address type="usb" bus="0" port="1"/>
</input>
<input type="mouse" bus="ps2"/>
<input type="keyboard" bus="ps2"/>
<hostdev mode="subsystem" type="pci" managed="yes">
<source>
<address domain="0x0000" bus="0x01" slot="0x00" function="0x0"/>
</source>
<address type="pci" domain="0x0000" bus="0x06" slot="0x00" function="0x0"/>
</hostdev>
<hostdev mode="subsystem" type="pci" managed="yes">
<source>
<address domain="0x0000" bus="0x01" slot="0x00" function="0x1"/>
</source>
<address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
</hostdev>
<hostdev mode="subsystem" type="usb" managed="yes">
<source>
<vendor id="0x1b1c"/>
<product id="0x1b49"/>
</source>
<address type="usb" bus="0" port="4"/>
</hostdev>
<hostdev mode="subsystem" type="usb" managed="yes">
<source>
<vendor id="0x264a"/>
<product id="0x1011"/>
</source>
<address type="usb" bus="0" port="5"/>
</hostdev>
<redirdev bus="usb" type="spicevmc">
<address type="usb" bus="0" port="2"/>
</redirdev>
<redirdev bus="usb" type="spicevmc">
<address type="usb" bus="0" port="3"/>
</redirdev>
<memballoon model="virtio">
<address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
</memballoon>
</devices>
</domain>
This is more of a comment, really...
I don't use libvirt myself, but as far as I can tell there aren't any audio devices in your config.
Here are the qemu command line options I use for guest (Win10 and others) audio output to PulseAudio output on -machine q35 :
-device ich9-intel-hda,addr=1f.1
-audiodev pa,id=snd0
-device hda-output,audiodev=snd0
Basically, audiodev pa is the host's PulseAudio, and device hda-output is a line-out device on the guest (which is routed through audiodev=snd0). ...And hda-output requires an ich9-intel-hda bus to connect to.
...I'd expect virt-manager to allow this type of setup.