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

[Michael Tokarev]

Ok, so this is migration from qemu-kvm 1.1 to qemu 1.3.  This officially
does not work because the two uses different memory layout.

There is a way to make this work from old qemu-kvm to new qemu, by
patching new qemu, but this introduces incompatibilities in other areas.

Hopefully there will be no more "major" transitions like this in the
future (I mean from qemu-kvm to qemu), so there's a chance that
snapshots made with 1.3 and up will be forward-compatible.

While this bugreport is filed with debian versions in mind, we in debian
especially did not apply any changes to upstream qemu in this area, --
as history shows, any attempt to "fix" this "downstream" only makes
things worse.

** Summary changed:

- QEmu 1.3.90 cannot restore a 1.1.2 live snapshot
+ QEmu 1.3+ cannot restore a 1.1- live snapshot made in qemu-kvm

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

Title:
  QEmu 1.3+ cannot restore a 1.1- live snapshot made in qemu-kvm

Status in QEMU:
  Confirmed

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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