[libvirt] Local qemu migration

[Daniel P. Berrange]

On Tue, Nov 04, 2014 at 10:49:44AM -0500, Cole Robinson wrote:
> On 11/04/2014 10:43 AM, Marc-André Lureau wrote:
> >Hi,
> >
> >Attempting to migration from session to system qemu fails because of the
> >following checks in  qemuMigrationCookieXMLParse():
> >
> >    if (STREQ(mig->remoteHostname, mig->localHostname)) {
> >         virReportError(VIR_ERR_INTERNAL_ERROR,
> >                        _("Attempt to migrate guest to the same host %s"),
> >                        mig->remoteHostname);
> >         goto error;
> >     }
> >....
> >     if (memcmp(mig->remoteHostuuid, mig->localHostuuid, VIR_UUID_BUFLEN) == 0) {
> >         virReportError(VIR_ERR_INTERNAL_ERROR,
> >                        _("Attempt to migrate guest to the same host %s"),
> >                        tmp);
> >         goto error;
> >
> >Is there a technical limitation for this error? If not, could it be overriden
> >with an additional flag?
> 
> Trying to prevent migrating to the same libvirtd instance which would
> historically deadlock in libvirt's qemu driver. But migrating session ->
> system shouldn't suffer from that problem, so maybe it should be smarter.
> 
> Maybe with the more fine grained locking these days we can actually make
> localhost migration work? Would be useful for testing

Nope, there's stuff that's on the filesystem that is tied to the QEMU
process and that would clash when migrating as you have two copies of
the same VM running at the sme time.

Regards,
Daniel
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