[Qemu-devel] [Bug 1123975] Re: QEmu 1.3.90 cannot restore a 1.1.2 live snapshot

[Francois Gouget]

> And one more thing -- from what to what are you trying to migrate?

I believe kvm is being used in both cases, though the command is
different with QEmu 1.3.90. I have redone tests where I kept libvirt set
to 1.0.2 and only switched between QEmu 1.1.2 and 1.3.90 to minimize the
changes. So here the only difference is 'apt-get install -t experimental
qemu'.

Here is what 'ps aux' shows me:

libvirt 1.0.2-2 + QEmu 1.1.2

127      12841 92.7  4.6 1078272 189128 ?      Sl   00:45  10:46
/usr/bin/kvm -name fgtbwinxp -S -M pc-1.1 -cpu
Penryn,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme
-enable-kvm -m 768 -smp 2,sockets=2,cores=1,threads=1 -uuid e624f2c9
-80fd-26c7-a38a-0f0e49b6b719 -no-user-config -nodefaults -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/fgtbwinxp.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime
-no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive
file=/mnt/storage1/qemu/fgtbwinxp.img,if=none,id=drive-
ide0-0-0,format=qcow2,cache=writeback -device ide-
hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive
if=none,id=drive-ide0-1-0,readonly=on,format=raw -device ide-
cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev
tap,fd=23,id=hostnet0 -device
rtl8139,netdev=hostnet0,id=net0,mac=52:54:00:c7:0e:97,bus=pci.0,addr=0x3
-chardev pty,id=charserial0 -device isa-
serial,chardev=charserial0,id=serial0 -device usb-tablet,id=input0 -vnc
127.0.0.1:0 -vga vmware -device intel-hda,id=sound0,bus=pci.0,addr=0x4
-device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device virtio-
balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -loadvm wtb

With libvirt 1.0.2-2 + QEmu 1.3.90
127      18709 39.7  0.8 1075732 35304 ?       Sl   01:39   0:05 
qemu-system-x86_64 -machine accel=kvm:tcg -name fgtbwinxp -S -M pc-1.1 -cpu 
Penryn,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme
 -m 768 -smp 2,sockets=2,cores=1,threads=1 -uuid 
e624f2c9-80fd-26c7-a38a-0f0e49b6b719 -no-user-config -nodefaults -chardev 
socket,id=charmonitor,path=/var/lib/libvirt/qemu/fgtbwinxp.monitor,server,nowait
 -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime 
-no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive 
file=/mnt/storage1/qemu/fgtbwinxp.img,if=none,id=drive-ide0-0-0,format=qcow2,cache=writeback
 -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 
-drive if=none,id=drive-ide0-1-0,readonly=on,format=raw -device 
ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev 
tap,fd=23,id=hostnet0 -device 
rtl8139,netdev=hostnet0,id=net0,mac=52:54:00:c7:0e:97,bus=pci.0,addr=0x3 
-chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 
-device usb-tablet,id=input0 -vnc 127.0.0.1:0 -vga vmware -device 
intel-hda,id=sound0,bus=pci.0,addr=0x4 -device 
hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 -device 
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -loadvm wtb


There's a wrinkle I missed in my original report: the behavior is different 
depending on whether the VM is already running or not.

$ virsh --connect qemu:///system destroy fgtbwinxp
$ virsh --connect qemu:///system snapshot-revert fgtbwinxp wtb;echo $?
0
# This command looks like it succeeds but in fact I see the VM booting Windows. 
So either the live state was not restored at all or it crashed before 
virt-viewer could connect.
$ virsh --connect qemu:///system snapshot-revert fgtbwinxp wtb;echo $?
error: operation failed: Error -22 while loading VM state
1


> But at any rate, I never recommended any sort of cross-version migration
> as in practice, despite countless efforts spent to make it to work, it
> almost always does NOT work.

Ouch. I expect to end up with about 50 live snapshots. It would be
pretty annoying to have to redo all of them every time I upgrade QEmu /
KVM :-(

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https://bugs.launchpad.net/bugs/1123975

Title:
  QEmu 1.3.90 cannot restore a 1.1.2 live snapshot

Status in QEMU:
  New

Bug description:
  I have upgraded to QEmu 1.3.90 (Debian 1.4.0~rc0+dfsg-1exp) but now
  when I try to restore a live snapshot made in QEmu 1.1.2 (Debian
  1.1.2+dfsg-5) I get the following message:

  virsh # snapshot-revert fgtbbuild wtb
  error: operation failed: Error -22 while loading VM state

  I have test VMs with live snapshots coreresponding to different
  testing configurations. So I typically revert the VMs in one of the
  live snapshots and run the tests. It would be pretty annoying to have
  to recreate all these live snapshots any time I upgrade QEmu.

  
  ipxe-qemu                              1.0.0+git-20120202.f6840ba-3
  qemu                                   1.4.0~rc0+dfsg-1exp
  qemu-keymaps                           1.4.0~rc0+dfsg-1exp
  qemu-kvm                               1.4.0~rc0+dfsg-1exp
  qemu-system                            1.4.0~rc0+dfsg-1exp
  qemu-system-arm                        1.4.0~rc0+dfsg-1exp
  qemu-system-common                     1.4.0~rc0+dfsg-1exp
  qemu-system-mips                       1.4.0~rc0+dfsg-1exp
  qemu-system-misc                       1.4.0~rc0+dfsg-1exp
  qemu-system-ppc                        1.4.0~rc0+dfsg-1exp
  qemu-system-sparc                      1.4.0~rc0+dfsg-1exp
  qemu-system-x86                        1.4.0~rc0+dfsg-1exp
  qemu-user                              1.4.0~rc0+dfsg-1exp
  qemu-utils                             1.4.0~rc0+dfsg-1exp
  libvirt-bin                            1.0.2-1
  libvirt-dev                            1.0.2-1
  libvirt-doc                            1.0.2-1
  libvirt-glib-1.0-0                     0.1.2-1
  libvirt0                               1.0.2-1
  libvirtodbc0                           6.1.4+dfsg1-5

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