[libvirt] KVM live migration with libvirt

Zvi Dubitzky DUBI at il.ibm.com
Fri Apr 17 15:05:30 UTC 2009

while trying a live migration for KVM with libvirt I call virDomainMigrate
() with the following parameters

virDomainMigrate (localDomain,

The connection with the target VM was established ok

Still I get the following error:

libvir: QEMU error : invalid argument in only tcp URIs are supported for 
KVM migrations

looking at the code of qemu_driver.c /qemudDomainMigratePrepare2()   is 
see the following code (for version2 case):

        if (!STREQLEN (uri_in, "tcp:", 6)) {
            qemudReportError (dconn, NULL, NULL, VIR_ERR_INVALID_ARG,
                  "%s", _("only tcp URIs are supported for KVM 
            goto cleanup;

 why is  the strncmp using length 6 and not 4 . I think this is the reason 
for the failure . If I put a NULL af ter the  "tcp:"  then
I do not fail here (strncmp stop at the first NULL)  but I fail one step 
later  pasrsing the port because the NULL  terminates the string 

Do we need a fix here ?


Zvi Dubitzky 
Virtualization and System Architecture   Email:dubi at il.ibm.com
IBM Haifa Research Laboratory    Phone: +972-4-8296182
Haifa, 31905, ISRAEL 

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