https://en.wikipedia.org/wiki/Trim_%28computing%29], when the VM's filesystem
marks blocks as unused after deleting files, the controller will relay this
information to the storage, which will then shrink the disk image accordingly.
-For the guest to be able to issue _TRIM_ commands, you must either use a
-*VirtIO SCSI* (or *VirtIO SCSI Single*) controller or set the *SSD emulation*
-option on the drive. Note that *Discard* is not supported on *VirtIO Block*
-drives.
+For the guest to be able to issue _TRIM_ commands, you must enable the *Discard*
+option on the drive. Some guest operating systems may also require the
+*SSD Emulation* flag to be set. Note that *Discard* on *VirtIO Block* drives is
+only supported on guests using Linux Kernel 5.0 or higher.
If you would like a drive to be presented to the guest as a solid-state drive
rather than a rotational hard disk, you can set the *SSD emulation* option on
which enables high performance, low-latency display mirroring between
host and guest.
+[[qm_audio_device]]
+Audio Device
+~~~~~~~~~~~~
+
+To add an audio device run the following command:
+
+----
+qm set <vmid> -audio0 device=<device>
+----
+
+Supported audio devices are:
+
+* `ich9-intel-hda`: Intel HD Audio Controller, emulates ICH9
+* `intel-hda`: Intel HD Audio Controller, emulates ICH6
+* `AC97`: Audio Codec '97, useful for older operating systems like Windows XP
+
+NOTE: The audio device works only in combination with SPICE. Remote protocols
+like Microsoft's RDP have options to play sound. To use the physical audio
+device of the host use device passthrough (see
+xref:qm_pci_passthrough[PCI Passthrough] and
+xref:qm_usb_passthrough[USB Passthrough]).
+
[[qm_startup_and_shutdown]]
Automatic Start and Shutdown of Virtual Machines
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~