Public bug reported:
Ubuntu 20.04 amd64. Originally thought this was virt-manager but tested
via virsh and found it appears to be caused by libvirt.
$ apt-cache policy libvirt-daemon virt-manager | grep -E '(^[^ ]|Installed)'
libvirt-daemon:
Installed: 6.0.0-0ubuntu8.14
virt-manager:
Installed: 1:2.2.1-3ubuntu2.1
$ virsh start 1804test
error: Failed to start domain 1804test
error: internal error: qemu unexpectedly closed the monitor:
2021-10-23T10:27:43.756117Z qemu-system-x86_64: -device
ide-cd,bus=ide.0,unit=1,drive=libvirt-1-format,id=ide0-0-1,bootindex=1,write-cache=on:
Failed to lock byte 100
Notice the "write-cache=on". In the domain definition it is set to
"none":
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw' cache='none'/>
<source
file='/srv/NAS/Sunny/Downloads/ISO/lubuntu-18.04-desktop-amd64.iso'/>
<target dev='hdb' bus='ide'/>
<readonly/>
<boot order='1'/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</disk>
I found that changing this (via virt-manager) sometimes does, and
sometimes does not, get reflected in the underlying call to qemu-system.
The reason for disabling caching is the ISOs are stored on an NFS file-
system and with caching the attempt to write-lock fails.
The full command-line captured as the machine was being started was:
/usr/bin/qemu-system-x86_64 -name guest=1804test,debug-threads=on
-S -object
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-23-1804test/master-key.aes
-machine pc-i440fx-focal,accel=kvm,usb=of
f,vmport=off,dump-guest-core=off -cpu
EPYC-Rome,x2apic=on,tsc-deadline=on,hypervisor=on,tsc-adjust=on,arch-capabilities=on,xsaves=on,cmp-legacy=on
,virt-ssbd=on,svme-addr-chk=on,rdctl-no=on,skip-l1dfl-vmentry=on,mds-no=on,pschange-mc-no=on,clwb=off,umip=off,rdpid=off,wbnoinvd=off,amd-stibp=of
f -m 4096 -overcommit mem-lock=off -smp 4,sockets=4,cores=1,threads=1 -uuid
7272b57e-3428-493c-b126-a7816af4f9e7 -no-user-config -nodefaults -char
dev socket,id=charmonitor,fd=31,server,nowait -mon
chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global
kvm-pit.lost_ti
ck_policy=delay -no-hpet -no-shutdown -global PIIX4_PM.disable_s3=1 -global
PIIX4_PM.disable_s4=1 -boot menu=on,strict=on -device ich9-usb-ehci1,i
d=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,masterb
us=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 -blockdev
{"driver":"file","filename":"/var/lib/libvirt/images/1804test.qcow2","node-name":"libvirt-2-storage",
"auto-read-only":true,"discard":"unmap"} -blockdev
{"node-name":"libvirt-2-format","read-only":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 -blockdev
{"driver":"file","filename":"/srv/NAS/Sunny/Downloads/
ISO/lubuntu-18.04-desktop-amd64.iso","node-name":"libvirt-1-storage","cache":{"direct":true,"no-flush":false},"auto-read-only":true,"discard":"unm
ap"} -blockdev
{"node-name":"libvirt-1-format","read-only":true,"cache":{"direct":true,"no-flush":false},"driver":"raw","file":"libvirt-1-storage"
} -device
ide-cd,bus=ide.0,unit=1,drive=libvirt-1-format,id=ide0-0-1,bootindex=1,write-cache=on
-netdev tap,fd=33,id=hostnet0 -device e1000,netdev
=hostnet0,id=net0,mac=52:54:00:c9:b5:59,bus=pci.0,addr=0x3 -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
-d
evice usb-tablet,id=input0,bus=usb.0,port=1 -spice
port=5900,addr=127.0.0.1,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 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -sandbox
on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny -msg
timestamp=on
The full domain definition:
<domain type='kvm'>
<name>1804test</name>
<uuid>7272b57e-3428-493c-b126-a7816af4f9e7</uuid>
<memory unit='KiB'>4194304</memory>
<currentMemory unit='KiB'>4194304</currentMemory>
<vcpu placement='static'>4</vcpu>
<os>
<type arch='x86_64' machine='pc-i440fx-focal'>hvm</type>
<bootmenu enable='yes'/>
</os>
<features>
<acpi/>
<apic/>
<vmport state='off'/>
</features>
<cpu mode='host-model' check='partial'/>
<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'/>
<source file='/var/lib/libvirt/images/1804test.qcow2'/>
<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' cache='none'/>
<source
file='/srv/NAS/Sunny/Downloads/ISO/lubuntu-18.04-desktop-amd64.iso'/>
<target dev='hdb' bus='ide'/>
<readonly/>
<boot order='1'/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</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>
<interface type='network'>
<mac address='52:54:00:c9:b5:59'/>
<source network='ipv6-open-routed'/>
<model type='e1000'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
</interface>
<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>
<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 type='address'/>
<image compression='off'/>
</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'/>
<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>
<memballoon model='virtio'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07'
function='0x0'/>
</memballoon>
</devices>
</domain>
** Affects: libvirt (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1948525
Title:
Alters Performance options > Cache mode causing start failure
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