trim with sparse qcow2 image

OpenCore-Boot.sh

@@ -52,12 +52,14 @@ args=(
   -smbios type=2
   -device ich9-intel-hda -device hda-duplex
   -device ich9-ahci,id=sata
-  -drive id=OpenCoreBoot,if=none,snapshot=on,format=qcow2,file="$REPO_PATH/OpenCore/OpenCore.qcow2"
-  -device ide-hd,bus=sata.2,drive=OpenCoreBoot
+  # Setup SSD trim support to keep qcow2 image sparse
+  -blockdev driver=qcow2,node-name=OpenCoreBoot,file.filename="$REPO_PATH/OpenCore/OpenCore.qcow2",file.aio=threads,file.driver=file,discard=unmap,detect-zeroes=unmap
+  -device ide-hd,bus=sata.2,drive=OpenCoreBoot,id=oc,rotation_rate=1
   -device ide-hd,bus=sata.3,drive=InstallMedia
   -drive id=InstallMedia,if=none,file="$REPO_PATH/BaseSystem.img",format=raw
-  -drive id=MacHDD,if=none,file="$REPO_PATH/mac_hdd_ng.img",format=qcow2
-  -device ide-hd,bus=sata.4,drive=MacHDD
+  # Again, setup SSD trim so macOS disk qcow2 image remains sparse
+  -blockdev driver=qcow2,node-name=MacHDD,file.driver=file,file.filename="$REPO_PATH/mac_hdd_ng.img",file.aio=threads,discard=unmap,detect-zeroes=unmap
+  -device ide-hd,bus=sata.4,drive=MacHDD,id=macssd,rotation_rate=1
   # -netdev tap,id=net0,ifname=tap0,script=no,downscript=no -device virtio-net-pci,netdev=net0,id=net0,mac=52:54:00:c9:18:27
   -netdev user,id=net0,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=net0,id=net0,mac=52:54:00:c9:18:27
   # -netdev user,id=net0 -device vmxnet3,netdev=net0,id=net0,mac=52:54:00:c9:18:27  # Note: Use this line for High Sierra

README.md

@@ -158,7 +158,11 @@ processors work just fine (even for macOS Sonoma).
   qemu-img create -f qcow2 mac_hdd_ng.img 256G
   ```
 
-  NOTE: Create this HDD image file on a fast SSD/NVMe disk for best results.
+> [!NOTE]
+> Create this HDD image file on a fast SSD/NVMe disk for best results.
+> 
+> To enable TRIM support inside macOS, you must run: `sudo trimforce enable` from
+> _inside the VM_ after it boots.
 
 * Now you are ready to install macOS 🚀
 
@@ -235,6 +239,12 @@ work, patience, and a bit of luck (perhaps?).
 
 ### Post-Installation
 
+* Run `sudo trimforce enable` to enable TRIM support on the macOS hard drive.
+  - NOTE: This is important so the `qcow2` image remains sparse, and does not
+    keep growing in size, even after deleting files to free space in the VM.
+  - This is supported by QEMU's `qcow2` image format block driver through the
+    `discard=unmap,detect-zeroes=unmap` parameters.
+
 * See [networking notes](networking-qemu-kvm-howto.txt) on how to setup networking in your VM, outbound and also inbound for remote access to your VM via SSH, VNC, etc.
 
 * To passthrough GPUs and other devices, see [these notes](notes.md#gpu-passthrough-notes).

macOS-libvirt-Catalina.xml

@@ -61,16 +61,16 @@
   <devices>
     <emulator>/usr/bin/qemu-system-x86_64</emulator>
     <disk type='file' device='disk'>
-      <driver name='qemu' type='qcow2' cache='writeback' io='threads'/>
+      <driver name='qemu' type='qcow2' cache='writeback' io='threads' discard='unmap' detect_zeroes='unmap'/>
       <source file='/home/CHANGEME/OSX-KVM/OpenCore/OpenCore.qcow2'/>
-      <target dev='sda' bus='sata'/>
+      <target dev='sda' bus='sata' rotation_rate='1'/>
       <boot order='2'/>
       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
     </disk>
     <disk type='file' device='disk'>
-      <driver name='qemu' type='qcow2' cache='writeback' io='threads'/>
+      <driver name='qemu' type='qcow2' cache='writeback' io='threads' discard='unmap' detect_zeroes='unmap'/>
       <source file='/home/CHANGEME/OSX-KVM/mac_hdd_ng.img'/>
-      <target dev='sdb' bus='sata'/>
+      <target dev='sdb' bus='sata' rotation_rate='1'/>
       <boot order='1'/>
       <address type='drive' controller='0' bus='0' target='0' unit='1'/>
     </disk>