Bug 1183869

Meet a issue like this bug, i guess maybe will be fix after this bug have been fixed:

1.prepare a vm have cpu settings like this:

  <cpu mode='host-passthrough'>
  </cpu>

2.
# virsh start test3
Domain test3 started

3.# virsh dumpxml test3 > test3.xml

4.change disk path to /tmp/test3.img
# vim test3.xml 

5.# virsh save test3 test3.save --xml test3.xml

Domain test3 saved to test3.save

[root@lhuang ~]# virsh restore test3.save --xml test3.xml
error: Failed to restore domain from test3.save
error: unsupported configuration: Target CPU model <null> does not match source Opteron_G5

Patches proposed upstream:

https://www.redhat.com/archives/libvir-list/2015-February/msg00687.html

And moving to POST:

commit cf2d4c603c37a58c7c6cacc87f0e78b45903ae7c
Author:     Michal Privoznik <mprivozn>
AuthorDate: Thu Feb 19 13:54:53 2015 +0100
Commit:     Michal Privoznik <mprivozn>
CommitDate: Wed Feb 25 09:28:54 2015 +0100

    qemu: Use correct flags for ABI stability check in SaveImageUpdateDef
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1183869
    
    Soo. you've successfully started yourself a domain. And since you want
    to use it on your host exclusively you are confident enough to
    passthrough the host CPU model, like this:
    
      <cpu mode='host-passthrough'/>
    
    Then, after a while, you want to save the domain into a file (e.g.
    virsh save dom dom.save). And here comes the trouble. The file consist
    of two parts: Libvirt header (containing domain XML among other
    things), and qemu migration data. Now, the domain XML in the header is
    formatted using special flags (VIR_DOMAIN_XML_SECURE |
    VIR_DOMAIN_XML_UPDATE_CPU | VIR_DOMAIN_XML_INACTIVE |
    VIR_DOMAIN_XML_MIGRATABLE).
    
    Then, on your way back from the bar, you think of changing something
    in the XML in the saved file (we have a command for it after all), say
    listen address for graphics console. So you successfully type in the
    command:
    
      virsh save-image-edit dom.save
    
    Change all the bits, and exit the editor. But instead of success
    you're left with sad error message:
    
      error: unsupported configuration: Target CPU model <null> does not
      match source Pentium Pro
    
    Sigh. Digging into the code you see lines, where we check for ABI
    stability. The new XML you've produced is compared with the old one
    from the saved file to see if qemu ABI will break or not. Wait, what?
    We are using different flags to parse the XML you've provided so we
    were just lucky it worked in some cases? Yep, that's right.
    
    Signed-off-by: Michal Privoznik <mprivozn>

commit c75f42f3318463b0555edac333c8f20d54b4d5dc
Author:     Ján Tomko <jtomko>
AuthorDate: Fri Feb 27 11:55:40 2015 +0100
Commit:     Ján Tomko <jtomko>
CommitDate: Fri Feb 27 12:01:31 2015 +0100

    Really fix XML formatting flags in SaveImageUpdateDef
    
    Commit cf2d4c6 used a logical or instead of bitwise or,
    effectively passing 1, that is VIR_DOMAIN_XML_INACTIVE.
    
    This was caught by a warning when building with clang.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1183869

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index e9aa0b5..e282464 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -5734,7 +5734,7 @@ qemuDomainSaveImageUpdateDef(virQEMUDriverPtr driver,
 
     if (!(newdef_migr = qemuDomainDefCopy(driver,
                                           newdef,
-                                          QEMU_DOMAIN_FORMAT_LIVE_FLAGS ||
+                                          QEMU_DOMAIN_FORMAT_LIVE_FLAGS |
                                           VIR_DOMAIN_XML_MIGRATABLE)))
         goto cleanup;


v1.2.13-rc2-6-gc75f42f

Verify this bug with libvirt-1.2.15-2.el7.x86_64:

1. a vm with host-passthrough cpu:

# virsh dumpxml test3
...
  <cpu mode='host-passthrough'>
    <numa>
      <cell id='0' cpus='0' memory='512000' unit='KiB'/>
      <cell id='1' cpus='1' memory='512000' unit='KiB'/>
    </numa>
  </cpu>
...

2. save it:

# virsh save test3 test3.save

Domain test3 saved to test3.save


3. use save-image-edit to change something:

# virsh save-image-dumpxml test3.save

  <cpu mode='host-passthrough'>
    <feature policy='require' name='bmi1'/>
    <feature policy='require' name='perfctr_nb'/>
    <feature policy='require' name='perfctr_core'/>
    <feature policy='require' name='topoext'/>
    <feature policy='require' name='nodeid_msr'/>
    <feature policy='require' name='tce'/>
    <feature policy='require' name='lwp'/>
    <feature policy='require' name='wdt'/>
    <feature policy='require' name='skinit'/>
    <feature policy='require' name='ibs'/>
    <feature policy='require' name='osvw'/>
    <feature policy='require' name='cr8legacy'/>
    <feature policy='require' name='extapic'/>
    <feature policy='require' name='cmp_legacy'/>
    <feature policy='require' name='fxsr_opt'/>
    <feature policy='require' name='mmxext'/>
    <feature policy='require' name='osxsave'/>
    <feature policy='require' name='monitor'/>
    <feature policy='require' name='ht'/>
    <feature policy='require' name='vme'/>
    <numa>
      <cell id='0' cpus='0' memory='512000' unit='KiB'/>
      <cell id='1' cpus='1' memory='512000' unit='KiB'/>
    </numa>
  </cpu>

# virsh save-image-edit test3.save
State file test3.save edited.

4. recheck the xml after edit the save file:

# virsh save-image-dumpxml test3.save


  <cpu mode='host-passthrough'>
    <feature policy='require' name='bmi1'/>
    <feature policy='require' name='perfctr_nb'/>
    <feature policy='require' name='perfctr_core'/>
    <feature policy='require' name='topoext'/>
    <feature policy='require' name='nodeid_msr'/>
    <feature policy='require' name='tce'/>
    <feature policy='require' name='lwp'/>
    <feature policy='require' name='wdt'/>
    <feature policy='require' name='skinit'/>
    <feature policy='require' name='ibs'/>
    <feature policy='require' name='osvw'/>
    <feature policy='require' name='cr8legacy'/>
    <feature policy='require' name='extapic'/>
    <feature policy='require' name='cmp_legacy'/>
    <feature policy='require' name='fxsr_opt'/>
    <feature policy='require' name='mmxext'/>
    <feature policy='require' name='osxsave'/>
    <feature policy='require' name='monitor'/>
    <feature policy='require' name='ht'/>
    <feature policy='require' name='vme'/>
    <numa>
      <cell id='0' cpus='0' memory='512000' unit='KiB'/>
      <cell id='1' cpus='1' memory='512000' unit='KiB'/>
    </numa>
  </cpu>

5. restore the guest and guest can start:

# virsh restore test3.save
Domain restored from test3.save

6. also test with --xml with save/restore works well

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2202.html