I just installed gnome-boxes in the current Ubuntu 20.04, created a VM and installed Linux in it (Ubuntu 20.04 and then Mint 19.3) and upon restart the VM doesn't come up again and trying to start it manually results in an immediate failure.

System info:
Description:	Ubuntu Focal Fossa (development branch)
Release:	20.04

Package info:
gnome-boxes:
  Zainstalowana: 3.36.0-1
  Kandydująca:   3.36.0-1
  Tabela wersji:
 *** 3.36.0-1 500
        500 http://pl.archive.ubuntu.com/ubuntu focal/universe amd64 Packages
        100 /var/lib/dpkg/status

Gnome Boxes Log:

Broker URL: qemu+unix:///session
Domain: boxes-unknown
UUID: 5f17c636-e353-4772-84fb-c45b2a30a2b7
Persistent: yes
Cpu time: 0
Memory: 2128991 KiB
Max memory: 8076596 KiB
CPUs: 4
State: GVIR_DOMAIN_STATE_SHUTOFF

Domain config:
------------------------------------------------------------
<domain type="kvm">
  <name>boxes-unknown</name>
  <uuid>5f17c636-e353-4772-84fb-c45b2a30a2b7</uuid>
  <title>linuxmint-19</title>
  <metadata>
    <boxes:gnome-boxes xmlns:boxes="https://wiki.gnome.org/Apps/Boxes">
      <os-state>installed</os-state>
      <media>/home/domin/Pobrane/linuxmint-19.3-cinnamon-64bit.iso</media>
    </boxes:gnome-boxes>
  </metadata>
  <memory unit="KiB">2128991</memory>
  <currentMemory unit="KiB">2128991</currentMemory>
  <vcpu placement="static">4</vcpu>
  <os firmware="bios">
    <type arch="x86_64" machine="pc-i440fx-focal">hvm</type>
    <boot dev="hd"/>
  </os>
  <features>
    <acpi/>
    <apic/>
  </features>
  <cpu mode="host-passthrough" check="none">
    <topology sockets="1" cores="2" threads="2"/>
  </cpu>
  <clock offset="utc">
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="pit" tickpolicy="delay"/>
    <timer name="hpet" present="no"/>
  </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" cache="writeback"/>
      <source file="/home/domin/.local/share/gnome-boxes/images/boxes-unknown"/>
      <target dev="hda" bus="ide"/>
      <address type="drive" controller="0" bus="0" target="0" unit="0"/>
    </disk>
    <disk type="file" device="cdrom">
      <driver name="qemu" type="raw"/>
      <source file="/home/domin/Pobrane/linuxmint-19.3-cinnamon-64bit.iso" startupPolicy="optional"/>
      <target dev="hdc" bus="ide"/>
      <readonly/>
      <address type="drive" controller="0" bus="1" target="0" unit="0"/>
    </disk>
    <controller type="usb" index="0" model="ich9-ehci1">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x7"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci1">
      <master startport="0"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x0" multifunction="on"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci2">
      <master startport="2"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x1"/>
    </controller>
    <controller type="usb" index="0" model="ich9-uhci3">
      <master startport="4"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x05" function="0x2"/>
    </controller>
    <controller type="pci" index="0" model="pci-root"/>
    <controller type="ide" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x01" function="0x1"/>
    </controller>
    <controller type="virtio-serial" index="0">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x06" function="0x0"/>
    </controller>
    <controller type="ccid" index="0">
      <address type="usb" bus="0" port="1"/>
    </controller>
    <interface type="user">
      <mac address="52:54:00:36:6a:1b"/>
      <model type="rtl8139"/>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x03" function="0x0"/>
    </interface>
    <smartcard mode="passthrough" type="spicevmc">
      <address type="ccid" controller="0" slot="0"/>
    </smartcard>
    <serial type="pty">
      <target type="isa-serial" port="0">
        <model name="isa-serial"/>
      </target>
    </serial>
    <console type="pty">
      <target type="serial" port="0"/>
    </console>
    <channel type="spicevmc">
      <target type="virtio" name="com.redhat.spice.0"/>
      <address type="virtio-serial" controller="0" bus="0" port="1"/>
    </channel>
    <channel type="spiceport">
      <source channel="org.spice-space.webdav.0"/>
      <target type="virtio" name="org.spice-space.webdav.0"/>
      <address type="virtio-serial" controller="0" bus="0" port="2"/>
    </channel>
    <input type="mouse" bus="ps2"/>
    <input type="keyboard" bus="ps2"/>
    <graphics type="spice">
      <listen type="none"/>
      <image compression="off"/>
      <gl enable="no"/>
    </graphics>
    <sound model="ich6">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x04" function="0x0"/>
    </sound>
    <video>
      <model type="qxl" ram="65536" vram="65536" vgamem="16384" heads="1" primary="yes">
        <acceleration accel3d="no"/>
      </model>
      <address type="pci" domain="0x0000" bus="0x00" slot="0x02" function="0x0"/>
    </video>
    <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>
    <redirdev bus="usb" type="spicevmc">
      <address type="usb" bus="0" port="4"/>
    </redirdev>
    <redirdev bus="usb" type="spicevmc">
      <address type="usb" bus="0" port="5"/>
    </redirdev>
    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x00" slot="0x07" function="0x0"/>
    </memballoon>
  </devices>
</domain>
------------------------------------------------------------

QEMU log:
------------------------------------------------------------
2020-03-29 10:09:39.231+0000: starting up libvirt version: 6.0.0, package: 0ubuntu6 (Christian Ehrhardt <email address hidden> Fri, 20 Mar 2020 10:34:19 +0100), qemu version: 4.2.0Debian 1:4.2-3ubuntu4, kernel: 5.4.0-18-generic, hostname: pupiaque3-ubuntu
LC_ALL=C \
PATH=/home/domin/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/jvm/java-8-oracle/bin:/usr/lib/jvm/java-8-oracle/db/bin:/usr/lib/jvm/java-8-oracle/jre/bin \
HOME=/home/domin \
USER=domin \
LOGNAME=domin \
XDG_CACHE_HOME=/home/domin/.config/libvirt/qemu/lib/domain-5-boxes-unknown/.cache \
QEMU_AUDIO_DRV=spice \
/usr/bin/qemu-system-x86_64 \
-name guest=boxes-unknown,debug-threads=on \
-S \
-object secret,id=masterKey0,format=raw,file=/home/domin/.config/libvirt/qemu/lib/domain-5-boxes-unknown/master-key.aes \
-machine pc-i440fx-focal,accel=kvm,usb=off,dump-guest-core=off \
-cpu host \
-m 2080 \
-overcommit mem-lock=off \
-smp 4,sockets=1,cores=2,threads=2 \
-uuid 5f17c636-e353-4772-84fb-c45b2a30a2b7 \
-no-user-config \
-nodefaults \
-chardev socket,id=charmonitor,fd=27,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc,driftfix=slew \
-global kvm-pit.lost_tick_policy=delay \
-no-hpet \
-no-reboot \
-global PIIX4_PM.disable_s3=1 \
-global PIIX4_PM.disable_s4=1 \
-boot menu=on,strict=on \
-device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x5.0x7 \
-device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x5 \
-device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x5.0x1 \
-device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x5.0x2 \
-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x6 \
-device usb-ccid,id=ccid0,bus=usb.0,port=1 \
-blockdev '{"driver":"file","filename":"/home/domin/.local/share/gnome-boxes/images/boxes-unknown","node-name":"libvirt-2-storage","cache":{"direct":false,"no-flush":false},"auto-read-only":true,"discard":"unmap"}' \
-blockdev '{"node-name":"libvirt-2-format","read-only":false,"cache":{"direct":false,"no-flush":false},"driver":"qcow2","file":"libvirt-2-storage","backing":null}' \
-device ide-hd,bus=ide.0,unit=0,drive=libvirt-2-format,id=ide0-0-0,bootindex=2,write-cache=on \
-blockdev '{"driver":"file","filename":"/home/domin/Pobrane/linuxmint-19.3-cinnamon-64bit.iso","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
-blockdev '{"node-name":"libvirt-1-format","read-only":true,"driver":"raw","file":"libvirt-1-storage"}' \
-device ide-cd,bus=ide.1,unit=0,drive=libvirt-1-format,id=ide0-1-0,bootindex=1 \
-netdev user,id=hostnet0 \
-device rtl8139,netdev=hostnet0,id=net0,mac=52:54:00:36:6a:1b,bus=pci.0,addr=0x3 \
-chardev spicevmc,id=charsmartcard0,name=smartcard \
-device ccid-card-passthru,chardev=charsmartcard0,id=smartcard0,bus=ccid0.0 \
-chardev pty,id=charserial0 \
-device isa-serial,chardev=charserial0,id=serial0 \
-chardev spicevmc,id=charchannel0,name=vdagent \
-device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.spice.0 \
-chardev spiceport,id=charchannel1,name=org.spice-space.webdav.0 \
-device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=org.spice-space.webdav.0 \
-spice port=0,disable-ticketing,image-compression=off,seamless-migration=on \
-device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,vram64_size_mb=0,vgamem_mb=16,max_outputs=1,bus=pci.0,addr=0x2 \
-device intel-hda,id=sound0,bus=pci.0,addr=0x4 \
-device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 \
-chardev spicevmc,id=charredir0,name=usbredir \
-device usb-redir,chardev=charredir0,id=redir0,bus=usb.0,port=2 \
-chardev spicevmc,id=charredir1,name=usbredir \
-device usb-redir,chardev=charredir1,id=redir1,bus=usb.0,port=3 \
-chardev spicevmc,id=charredir2,name=usbredir \
-device usb-redir,chardev=charredir2,id=redir2,bus=usb.0,port=4 \
-chardev spicevmc,id=charredir3,name=usbredir \
-device usb-redir,chardev=charredir3,id=redir3,bus=usb.0,port=5 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
2020-03-29 10:09:39.231+0000: Domain id=5 is tainted: host-cpu
char device redirected to /dev/pts/0 (label charserial0)
2020-03-29T10:24:26.393831Z qemu-system-x86_64: warning: Spice: display-channel.c:2437:display_channel_validate_surface: canvas address is 0x7fc02cea8b18 for 0 (and is NULL)
2020-03-29T10:24:26.394302Z qemu-system-x86_64: warning: Spice: display-channel.c:2439:display_channel_validate_surface: failed on 0
2020-03-29 10:24:38.773+0000: shutting down, reason=shutdown
2020-03-29 10:24:38.850+0000: shutting down, reason=failed
2020-03-29 10:24:41.094+0000: shutting down, reason=failed
------------------------------------------------------------