[Qemu-devel] Are VM snapshots on Ubuntu host compatible with Fedora host?

[David Barrett <dbarrett@quinthar.com>]

Should I be able to use "loadvm" on one computer to load a VM snapshot 
created with "savevm" on another?

Essentially, I've got my image working great on a local box (dual CPU 
Ubuntu), and  I've got qemu working on one of my servers (quad CPU 
Fedora Core 4), so I've uploaded the guest image to the server and tried 
to start it.  Unfortunately, it reliably spits out the following:

 > qemu -nographic -serial vc -smb qemu -kernel-kqemu -localtime -m 512 
-monitor stdio -loadvm boot winxp.qcow2

(qemu) qemu: warning: error while loading state for instance 0x0 of 
device 'ram'
qemu: fatal: triple fault
EAX=000676c8 EBX=ffdff000 ECX=ffdffc50 EDX=e0010031
ESI=80559320 EDI=80559580 EBP=ffdff980 ESP=805508d4
EIP=806f372a EFL=00010202 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0023 00000000 ffffffff 00cff300
CS =0008 00000000 ffffffff 00cffb00
SS =0010 00000000 ffffffff 00cff300
DS =0023 00000000 ffffffff 00cff300
FS =0030 ffdff000 00001fff ff40f3df
GS =0000 00000000 00000000 00000000
LDT=0000 00000000 00000000 00008000
TR =0028 80042000 000020ab 80008904
GDT=     8003f000 000003ff
IDT=     8003f400 000007ff
CR0=e001003b CR2=8003f440 CR3=00039000 CR4=000006d8
CCS=00000015 CCD=00000000 CCO=EFLAGS
FCW=027f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 
XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 
XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 
XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 
XMM07=00000000000000000000000000000000

If I take out the "-loadvm boot" clause, it loads fine (well, it uses 
100% CPU, but that's a different matter).  And I can see that the 
snapshot is actually there:

(qemu) info snapshots
Snapshot devices: ide0-hd0
Snapshot list (from ide0-hd0):
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         boot                    97M 2008-03-07 19:04:46   01:24:45.824
(qemu)

But it consistently crashes when I attempt to load the VM, whether using 
"-loadvm" at the command line or "loadvm" from the monitor.  Similarly, 
I can save/load *new* snapshots just fine:

(qemu) savevm blah
(qemu) info snapshots
Snapshot devices: ide0-hd0
Snapshot list (from ide0-hd0):
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         boot                    97M 2008-03-07 19:04:46   01:24:45.824
2         blah                   2.8M 2008-03-19 19:06:16   00:01:02.286
(qemu) loadvm blah
(qemu)

What I'm wondering is:

1) Is this supposed to work?  Or are VM snapshots saved on one host 
unable to be loaded on another?

2) Do you have any tips for how to fix the above problem?  I've tried an 
old patch that I found from the list that looked promising, but didn't help:

http://www.mail-archive.com/kvm-devel@lists.sourceforge.net/msg01624.html

Thanks!

-david