libvirt users - Feb 2022 - Hugepages -- "Memory backend 'pc.ram' not found"

On 2/21/22 17:12, Charles Polisher wrote:

Hey, please the list on CC for benefit of others, e.g. when somebody
runs into the same problem they can find the discussion in the archive.
> On 2/21/22 01:54, Michal Pr?vozn?k wrote:
> 
>> On 2/20/22 04:07, Charles Polisher wrote:
>>> Hello,
>>>
>>> After defining hugepages, as documented at
>>> https://libvirt.org/formatdomain.html#memory-backing ,
>>> when I start the guest, I get a dialogue
>>> box that says:
>>>
>>> ???? Error starting domain: internal error: qemu unexpectedly
>>> ???? closed the monitor: 2022-02-20T01:10:36.520955Z
>>> ???? qemu-system-x86_64: Memory backend 'pc.ram' not found
>>> ???? Traceback (most recent call last):
>>> ?? ? ? File
"/usr/share/virt-manager/virtManager/asyncjob.py", line 65,
>>> in cb_wrapper
>>> ?? ?? ?? callback(asyncjob, *args, **kwargs)
>>> ?? ? ? File
"/usr/share/virt-manager/virtManager/asyncjob.py", line 101,
>>> in tmpcb
>>> ?? ? ? ? callback(*args, **kwargs)
>>> ?????? File
>>>
"/usr/share/virt-manager/virtManager/object/libvirtobject.py", line
57,
>>> in newfn
>>> ???????? ret = fn(self, *args, **kwargs)
>>> ?????? File
"/usr/share/virt-manager/virtManager/object/domain.py", line
>>> 1329, in startup
>>> ?? ? ? ? self._backend.create()
>>> ?????? File
"/usr/lib64/python3.9/site-packages/libvirt.py", line 1353,
>>> in create
>>> ?? ? ? ? raise libvirtError('virDomainCreate() failed'
>>>
>>> After backing out changes, guest starts normally.
>>> I searched online for the error message, but found nothing useful.
>>> The hypervisor is running libvirtd (libvirt) 7.8.0 and QEMU
emulator
>>> version 6.1.0,
>>> both build from source. I've got plenty of hugepages available.
>>> The domain's XML definition is attached.
>> Hey, can you share your domain XML and the generated cmd line? The
>> latter should be found in /var/log/libvirt/qemu/$domain.log
>>
>> Thanks,
>> Michal
> 
> Thanks for your reply. As requested, the domain XML:
> 
> ??? <domain type="kvm">
> ????? <name>slacky-0</name>
> ????? <uuid>4a67eb39-9b92-8b8a-97ba-7e1250d56b07</uuid>
> ????? <title>slacky-0</title>
> ????? <description>elided</description>
> ????? <memory unit="KiB">4194304</memory>
> ????? <currentMemory
unit="KiB">4194304</currentMemory>
> ????? <memoryBacking>
> ??????? <hugepages>
> ????????? <page size="4194304" unit="KiB"/>
This does not look correct. This is on x86_64 and there is no such size
for hugepages, only 2MiB and 1GiB.
> ??????? </hugepages>
> ????? </memoryBacking>
> ????? <vcpu placement="static">2</vcpu>
> ????? <os>
> ??????? <type arch="x86_64"
machine="pc-i440fx-5.1">hvm</type>
> ??????? <bootmenu enable="no"/>
> ????? </os>
> ????? <features>
> ??????? <acpi/>
> ??????? <apic/>
> ??????? <pae/>
> ????? </features>
> ????? <cpu mode="custom" match="exact"
check="none">
> ??????? <model fallback="forbid">kvm64</model>
> ????? </cpu>
> ????? <clock offset="utc"/>
> ????? <on_poweroff>destroy</on_poweroff>
> ????? <on_reboot>restart</on_reboot>
> ????? <on_crash>restart</on_crash>
> ????? <devices>
> ??????? <emulator>/usr/bin/qemu-system-x86_64</emulator>
> ??????? <disk type="file" device="cdrom">
> ????????? <driver name="qemu" type="raw"/>
> ????????? <target dev="hdc" bus="ide"/>
> ????????? <readonly/>
> ????????? <address type="drive" controller="0"
bus="1" target="0"
> unit="0"/>
> ??????? </disk>
> ??????? <disk type="file" device="disk">
> ????????? <driver name="qemu" type="qcow2"
cache="writethrough"/>
> ????????? <source
file="/mnt/nvme1/VIRTUAL_MACHINES/slacky-0.qcow2"/>
> ????????? <target dev="vda" bus="virtio"/>
> ????????? <boot order="1"/>
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x09"
> function="0x0"/>
> ??????? </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="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="0x07"
> function="0x0"/>
> ??????? </controller>
> ??????? <controller type="scsi" index="0"
model="virtio-scsi">
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x08"
> function="0x0"/>
> ??????? </controller>
> ??????? <controller type="pci" index="0"
model="pci-root"/>
> ??????? <interface type="network">
> ????????? <mac address="52:54:00:c3:93:40"/>
> ????????? <source network="default"/>
> ????????? <model type="virtio"/>
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x03"
> function="0x0"/>
> ??????? </interface>
> ??????? <serial type="file">
> ????????? <source path="/tmp/myconsoleoutput.txt"/>
> ????????? <target type="isa-serial" port="0">
> ??????????? <model name="isa-serial"/>
> ????????? </target>
> ??????? </serial>
> ??????? <console type="file">
> ????????? <source path="/tmp/myconsoleoutput.txt"/>
> ????????? <target type="serial" port="0"/>
> ??????? </console>
> ??????? <input type="tablet" bus="usb">
> ????????? <address type="usb" bus="0"
port="1"/>
> ??????? </input>
> ??????? <input type="mouse" bus="ps2"/>
> ??????? <input type="keyboard" bus="ps2"/>
> ??????? <graphics type="spice" autoport="yes"
listen="127.0.0.1">
> ????????? <listen type="address"
address="127.0.0.1"/>
> ??????? </graphics>
> ??????? <sound model="ich9">
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x04"
> function="0x0"/>
> ??????? </sound>
> ??????? <audio id="1" type="spice"/>
> ??????? <video>
> ????????? <model type="qxl" ram="65536"
vram="65536" vgamem="16384"
> heads="1" primary="yes"/>
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x02"
> function="0x0"/>
> ??????? </video>
> ??????? <memballoon model="virtio">
> ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x06"
> function="0x0"/>
> ??????? </memballoon>
> ????? </devices>
> ??? </domain>
> 
> 
> And the guest log with the generated command line:
> 
> ??? 2022-02-20 01:13:12.985+0000: starting up libvirt version: 7.8.0,
> qemu version: 6.1.0, kernel: 5.15.19, hostname: godzilla.peecee3.com
> ??? LC_ALL=C \
> ??? PATH=/sbin:/usr/sbin:/bin:/usr/bin \
> ??? HOME=/var/lib/libvirt/qemu/domain-34-slacky-0 \
> XDG_DATA_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.local/share \
> ??? XDG_CACHE_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.cache \
> XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.config \
> ??? /usr/bin/qemu-system-x86_64 \
> ??? -name guest=slacky-0,process=qemu:slacky-0,debug-threads=on \
> ??? -S \
> ??? -object
>
'{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/var/lib/libvirt/qemu/domain-34-slacky-0/master-key.aes"}'
> \
> ??? -machine
> pc-i440fx-5.1,accel=kvm,usb=off,dump-guest-core=off,memory-backend=pc.ram \
So this instructs qemu to use a memory device wih id='pc.ram' as the
default/generic memory for the guest..
> ??? -cpu kvm64 \
> ??? -m 4096 \
> ??? -overcommit mem-lock=off \
.. but we never generate such device. Here libvirt should have generated
-object memory-backend-file,id=pc.ram,path=/hugepages/...

And I think I know why. Let me post a patch.
> ??? -smp 2,sockets=2,cores=1,threads=1 \
> ??? -uuid 4a67eb39-9b92-8b8a-97ba-7e1250d56b07 \
> ??? -no-user-config \
> ??? -nodefaults \
> ??? -chardev socket,id=charmonitor,fd=34,server=on,wait=off \
> ??? -mon chardev=charmonitor,id=monitor,mode=control \
> ??? -rtc base=utc \
> ??? -no-shutdown \
> ??? -boot menu=off,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-scsi-pci,id=scsi0,bus=pci.0,addr=0x8 \
> ??? -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x7 \
> ??? -device ide-cd,bus=ide.1,unit=0,id=ide0-1-0 \
> ??? -blockdev
>
'{"driver":"file","filename":"/mnt/nvme1/VIRTUAL_MACHINES/slacky-0.qcow2","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":false},"auto-read-only":true,"discard":"unmap"}'
> \
> ??? -blockdev
>
'{"node-name":"libvirt-1-format","read-only":false,"cache":{"direct":false,"no-flush":false},"driver":"qcow2","file":"libvirt-1-storage","backing":null}'
> \
> ??? -device
>
virtio-blk-pci,bus=pci.0,addr=0x9,drive=libvirt-1-format,id=virtio-disk0,bootindex=1,write-cache=off
> \
> ??? -netdev tap,fd=58,id=hostnet0,vhost=on,vhostfd=60 \
> ??? -device
>
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:c3:93:40,bus=pci.0,addr=0x3
> \
> ??? -add-fd set=3,fd=62 \
> ??? -chardev file,id=charserial0,path=/dev/fdset/3,append=on \
> ??? -device isa-serial,chardev=charserial0,id=serial0 \
> ??? -device usb-tablet,id=input0,bus=usb.0,port=1 \
> ??? -audiodev id=audio1,driver=spice \
> ??? -spice
> port=5901,addr=127.0.0.1,disable-ticketing=on,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 ich9-intel-hda,id=sound0,bus=pci.0,addr=0x4 \
> ??? -device
> hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0,audiodev=audio1 \
> ??? -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 \
> ??? -msg timestamp=on
> ??? 2022-02-20T01:13:13.136602Z qemu-system-x86_64: Memory backend
> 'pc.ram' not found
> ??? 2022-02-20 01:13:13.186+0000: shutting down, reason=failed
> 
> Again, thank you!
Michal

On 2/22/22 00:25, Michal Pr?vozn?k wrote:
> On 2/21/22 17:12, Charles Polisher wrote:
>
> Hey, please the list on CC for benefit of others, e.g. when somebody
> runs into the same problem they can find the discussion in the archive.
Oops... unintentional.
>> On 2/21/22 01:54, Michal Pr?vozn?k wrote:
>>> On 2/20/22 04:07, Charles Polisher wrote:
>>>> Hello,
>>>>
>>>> After defining hugepages, as documented at
>>>> https://libvirt.org/formatdomain.html#memory-backing ,
>>>> when I start the guest, I get a dialogue
>>>> box that says:
>>>>
>>>>  ???? Error starting domain: internal error: qemu unexpectedly
>>>>  ???? closed the monitor: 2022-02-20T01:10:36.520955Z
>>>>  ???? qemu-system-x86_64: Memory backend 'pc.ram' not
found
>>>>  ???? Traceback (most recent call last):
>>>>  ?? ? ? File
"/usr/share/virt-manager/virtManager/asyncjob.py", line 65,
>>>> in cb_wrapper
>>>>  ?? ?? ?? callback(asyncjob, *args, **kwargs)
>>>>  ?? ? ? File
"/usr/share/virt-manager/virtManager/asyncjob.py", line 101,
>>>> in tmpcb
>>>>  ?? ? ? ? callback(*args, **kwargs)
>>>>  ?????? File
>>>>
"/usr/share/virt-manager/virtManager/object/libvirtobject.py", line
57,
>>>> in newfn
>>>>  ???????? ret = fn(self, *args, **kwargs)
>>>>  ?????? File
"/usr/share/virt-manager/virtManager/object/domain.py", line
>>>> 1329, in startup
>>>>  ?? ? ? ? self._backend.create()
>>>>  ?????? File
"/usr/lib64/python3.9/site-packages/libvirt.py", line 1353,
>>>> in create
>>>>  ?? ? ? ? raise libvirtError('virDomainCreate() failed'
>>>>
>>>> After backing out changes, guest starts normally.
>>>> I searched online for the error message, but found nothing
useful.
>>>> The hypervisor is running libvirtd (libvirt) 7.8.0 and QEMU
emulator
>>>> version 6.1.0,
>>>> both build from source. I've got plenty of hugepages
available.
>>>> The domain's XML definition is attached.
>>> Hey, can you share your domain XML and the generated cmd line? The
>>> latter should be found in /var/log/libvirt/qemu/$domain.log
>>>
>>> Thanks,
>>> Michal
>> Thanks for your reply. As requested, the domain XML:
>>
>>  ??? <domain type="kvm">
>>  ????? <name>slacky-0</name>
>>  ????? <uuid>4a67eb39-9b92-8b8a-97ba-7e1250d56b07</uuid>
>>  ????? <title>slacky-0</title>
>>  ????? <description>elided</description>
>>  ????? <memory unit="KiB">4194304</memory>
>>  ????? <currentMemory
unit="KiB">4194304</currentMemory>
>>  ????? <memoryBacking>
>>  ??????? <hugepages>
>>  ????????? <page size="4194304" unit="KiB"/>
>>
>> This does not look correct. This is on x86_64 and there is no such size
>> for hugepages, only 2MiB and 1GiB.
Interesting. I had originally specified a different page size
and units (probably GiB), but "virsh edit" rewrote the value
after I completed the edit, with the result above.
>>  ??????? </hugepages>
>>  ????? </memoryBacking>
>>  ????? <vcpu placement="static">2</vcpu>
>>  ????? <os>
>>  ??????? <type arch="x86_64"
machine="pc-i440fx-5.1">hvm</type>
>>  ??????? <bootmenu enable="no"/>
>>  ????? </os>
>>  ????? <features>
>>  ??????? <acpi/>
>>  ??????? <apic/>
>>  ??????? <pae/>
>>  ????? </features>
>>  ????? <cpu mode="custom" match="exact"
check="none">
>>  ??????? <model fallback="forbid">kvm64</model>
>>  ????? </cpu>
>>  ????? <clock offset="utc"/>
>>  ????? <on_poweroff>destroy</on_poweroff>
>>  ????? <on_reboot>restart</on_reboot>
>>  ????? <on_crash>restart</on_crash>
>>  ????? <devices>
>>  ??????? <emulator>/usr/bin/qemu-system-x86_64</emulator>
>>  ??????? <disk type="file" device="cdrom">
>>  ????????? <driver name="qemu" type="raw"/>
>>  ????????? <target dev="hdc" bus="ide"/>
>>  ????????? <readonly/>
>>  ????????? <address type="drive" controller="0"
bus="1" target="0"
>> unit="0"/>
>>  ??????? </disk>
>>  ??????? <disk type="file" device="disk">
>>  ????????? <driver name="qemu" type="qcow2"
cache="writethrough"/>
>>  ????????? <source
file="/mnt/nvme1/VIRTUAL_MACHINES/slacky-0.qcow2"/>
>>  ????????? <target dev="vda" bus="virtio"/>
>>  ????????? <boot order="1"/>
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x09"
>> function="0x0"/>
>>  ??????? </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="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="0x07"
>> function="0x0"/>
>>  ??????? </controller>
>>  ??????? <controller type="scsi" index="0"
model="virtio-scsi">
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x08"
>> function="0x0"/>
>>  ??????? </controller>
>>  ??????? <controller type="pci" index="0"
model="pci-root"/>
>>  ??????? <interface type="network">
>>  ????????? <mac address="52:54:00:c3:93:40"/>
>>  ????????? <source network="default"/>
>>  ????????? <model type="virtio"/>
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x03"
>> function="0x0"/>
>>  ??????? </interface>
>>  ??????? <serial type="file">
>>  ????????? <source path="/tmp/myconsoleoutput.txt"/>
>>  ????????? <target type="isa-serial"
port="0">
>>  ??????????? <model name="isa-serial"/>
>>  ????????? </target>
>>  ??????? </serial>
>>  ??????? <console type="file">
>>  ????????? <source path="/tmp/myconsoleoutput.txt"/>
>>  ????????? <target type="serial" port="0"/>
>>  ??????? </console>
>>  ??????? <input type="tablet" bus="usb">
>>  ????????? <address type="usb" bus="0"
port="1"/>
>>  ??????? </input>
>>  ??????? <input type="mouse" bus="ps2"/>
>>  ??????? <input type="keyboard" bus="ps2"/>
>>  ??????? <graphics type="spice" autoport="yes"
listen="127.0.0.1">
>>  ????????? <listen type="address"
address="127.0.0.1"/>
>>  ??????? </graphics>
>>  ??????? <sound model="ich9">
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x04"
>> function="0x0"/>
>>  ??????? </sound>
>>  ??????? <audio id="1" type="spice"/>
>>  ??????? <video>
>>  ????????? <model type="qxl" ram="65536"
vram="65536" vgamem="16384"
>> heads="1" primary="yes"/>
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x02"
>> function="0x0"/>
>>  ??????? </video>
>>  ??????? <memballoon model="virtio">
>>  ????????? <address type="pci" domain="0x0000"
bus="0x00" slot="0x06"
>> function="0x0"/>
>>  ??????? </memballoon>
>>  ????? </devices>
>>  ??? </domain>
>>
>>
>> And the guest log with the generated command line:
>>
>>  ??? 2022-02-20 01:13:12.985+0000: starting up libvirt version: 7.8.0,
>> qemu version: 6.1.0, kernel: 5.15.19, hostname: godzilla.peecee3.com
>>  ??? LC_ALL=C \
>>  ??? PATH=/sbin:/usr/sbin:/bin:/usr/bin \
>>  ??? HOME=/var/lib/libvirt/qemu/domain-34-slacky-0 \
>> XDG_DATA_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.local/share \
>>  ??? XDG_CACHE_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.cache \
>> XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain-34-slacky-0/.config \
>>  ??? /usr/bin/qemu-system-x86_64 \
>>  ??? -name guest=slacky-0,process=qemu:slacky-0,debug-threads=on \
>>  ??? -S \
>>  ??? -object
>>
'{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/var/lib/libvirt/qemu/domain-34-slacky-0/master-key.aes"}'
>> \
>>  ??? -machine
>>
pc-i440fx-5.1,accel=kvm,usb=off,dump-guest-core=off,memory-backend=pc.ram \
> So this instructs qemu to use a memory device wih id='pc.ram' as
the
> default/generic memory for the guest..
>
>>  ??? -cpu kvm64 \
>>  ??? -m 4096 \
>>  ??? -overcommit mem-lock=off \
> .. but we never generate such device. Here libvirt should have generated
> -object memory-backend-file,id=pc.ram,path=/hugepages/...
>
> And I think I know why. Let me post a patch.
>
>>  ??? -smp 2,sockets=2,cores=1,threads=1 \
>>  ??? -uuid 4a67eb39-9b92-8b8a-97ba-7e1250d56b07 \
>>  ??? -no-user-config \
>>  ??? -nodefaults \
>>  ??? -chardev socket,id=charmonitor,fd=34,server=on,wait=off \
>>  ??? -mon chardev=charmonitor,id=monitor,mode=control \
>>  ??? -rtc base=utc \
>>  ??? -no-shutdown \
>>  ??? -boot menu=off,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-scsi-pci,id=scsi0,bus=pci.0,addr=0x8 \
>>  ??? -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x7 \
>>  ??? -device ide-cd,bus=ide.1,unit=0,id=ide0-1-0 \
>>  ??? -blockdev
>>
'{"driver":"file","filename":"/mnt/nvme1/VIRTUAL_MACHINES/slacky-0.qcow2","node-name":"libvirt-1-storage","cache":{"direct":false,"no-flush":false},"auto-read-only":true,"discard":"unmap"}'
>> \
>>  ??? -blockdev
>>
'{"node-name":"libvirt-1-format","read-only":false,"cache":{"direct":false,"no-flush":false},"driver":"qcow2","file":"libvirt-1-storage","backing":null}'
>> \
>>  ??? -device
>>
virtio-blk-pci,bus=pci.0,addr=0x9,drive=libvirt-1-format,id=virtio-disk0,bootindex=1,write-cache=off
>> \
>>  ??? -netdev tap,fd=58,id=hostnet0,vhost=on,vhostfd=60 \
>>  ??? -device
>>
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:c3:93:40,bus=pci.0,addr=0x3
>> \
>>  ??? -add-fd set=3,fd=62 \
>>  ??? -chardev file,id=charserial0,path=/dev/fdset/3,append=on \
>>  ??? -device isa-serial,chardev=charserial0,id=serial0 \
>>  ??? -device usb-tablet,id=input0,bus=usb.0,port=1 \
>>  ??? -audiodev id=audio1,driver=spice \
>>  ??? -spice
>> port=5901,addr=127.0.0.1,disable-ticketing=on,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 ich9-intel-hda,id=sound0,bus=pci.0,addr=0x4 \
>>  ??? -device
>> hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0,audiodev=audio1 \
>>  ??? -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 \
>>  ??? -msg timestamp=on
>>  ??? 2022-02-20T01:13:13.136602Z qemu-system-x86_64: Memory backend
>> 'pc.ram' not found
>>  ??? 2022-02-20 01:13:13.186+0000: shutting down, reason=failed
>>
>> Again, thank you!
>>
>> Michal
Many thanks!