[Qemu-devel] Bug (?) vl.c/qemu_loadvm() said "qemu: warning: instance" restoring from LUN/partition

[Daniel Schwager]

Hi list,

we use fedora-core8-xen linux, which is based 
on the qemu-0.9.0-5.fc8  and uses 
a qemue device_model (/usr/lib64/xen/bin/qemu-dm).

If I try to restore a saved domain, all works fine,
if the save-file is a plain file on the filesystem.

If I restore a domain from a LUN (e.g. /dev/sdb1), which
has MORE space than the filesize from the "xm save /tmp/file",
I got a lot of errors (about in /var/log/xen/qemu-dm.<PID>.log:
....
qemu: warning: instance 0x0 of device '' not present in current VM
qemu: warning: instance 0x0 of device '' not present in current VM
qemu: warning: instance 0x0 of device '' not present in current VM
qemu: warning: instance 0x0 of device '' not present in current VM
qemu: warning: instance 0x0 of device '' not present in current VM
.....
        
address@hidden xen]# grep "qemu: warning: instance 0x0 of device"  
qemu-dm.9747.log |wc -l
47875

 address@hidden xen]# ls -lah qemu-dm.9747.log
-rw-r--r-- 1 root root 3.1M 2008-02-22 21:41 qemu-dm.9747.log


You can also reproduce this bug by creating a save file
        xm save <domain-id> /tmp/file

and append some additional space to it
        dd if=/dev/zero of=/tmp/zero bs=1k count=100
        cat /tmp/file /tmp/zero > /tmp/filezero

and restore the domain 
        xm restore /tmp/filezero

and look at qemu-dm.PID.log.


Saving to LVM-Luns or iscsi-published LUN's is maybe a usecase for some people
e.g. for me (-:

Is this a bug or should you scan/interpret the save-file to the EOF ?

Could I restore from a LUN without errors ?

What's the minimum size of the LUN saving the domain to. 
I guess domain_memory + 15.899MB ... is it ?

Regards

Danny


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