[gnome-boxes/discard-unmap-for-virtio-blk: 3/3] vm-configurator: Pass discard "unmap" to virtio-blk disks

[Felipe Borges <felipeborges src gnome org>]

commit e52101c9de6c350cd15ab537547e44558bf154b0
Author: Felipe Borges <felipeborges gnome org>
Date:   Mon Nov 2 15:35:36 2020 +0100

    vm-configurator: Pass discard "unmap" to virtio-blk disks
    
    Ever since QEMU 4.0, virtio-blk disks have discard support[0]. For
    this reason, we don't need to migrate to virtio-scsi[1] to benefit from
    discard support.
    
    See also https://chrisirwin.ca/posts/discard-with-kvm-2020/
    
    [0] https://bugzilla.redhat.com/1672680
    [1] https://bugzilla.redhat.com/1152037
    
    Fixes #35

 src/vm-configurator.vala | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/src/vm-configurator.vala b/src/vm-configurator.vala
index ee8cf133..f2a50bb8 100644
--- a/src/vm-configurator.vala
+++ b/src/vm-configurator.vala
@@ -343,16 +343,21 @@ public static void set_target_media_config (Domain         domain,
         var disk = new DomainDisk ();
         disk.set_type (DomainDiskType.FILE);
         disk.set_guest_device_type (DomainDiskGuestDeviceType.DISK);
-        disk.set_driver_name ("qemu");
-        disk.set_driver_format (DomainDiskFormat.QCOW2);
         disk.set_source (target_path);
-        disk.set_driver_cache (DomainDiskCacheType.WRITEBACK);
+
+        var driver = new DomainDiskDriver ();
+        driver.set_name ("qemu");
+        driver.set_format (DomainDiskFormat.QCOW2);
+        driver.set_cache (DomainDiskCacheType.WRITEBACK);
+        disk.set_driver (driver);
 
         var dev_letter_str = ((char) (dev_index + 97)).to_string ();
         if (install_media.supports_virtio_disk || install_media.supports_virtio1_disk) {
             debug ("Using virtio controller for the main disk");
             disk.set_target_bus (DomainDiskBus.VIRTIO);
             disk.set_target_dev ("vd" + dev_letter_str);
+
+            driver.set_discard (DomainDiskDriverDiscard.UNMAP);
         } else {
             if (install_media.prefers_q35) {
                 debug ("Using SATA controller for the main disk");