Re: [libvirt] libxl: Issues with virt-manager when used to manager Xen domains

On 25.03.2014 16:36, Daniel P. Berrange wrote: > On Tue, Mar 25, 2014 at 04:22:54PM +0100, Stefan Bader wrote: >> This started off with some regression testing after going forward to Xen-4.4. We >> currently would pair that with a libvirt version 1.2.2 and right now operations >> through virsh seem to be working (mostly) well. But when using virt-manager (not >> the most up-to-date versions but some combinations that quite likely will occur >> (0.9.1 and 0.9.5)) there are some issues. >> >> Two symptoms seem to be caused by the same underlying problem which is caused by >> the way virt-manager interacts with libvirt. That seems to be that virt-manager >> acquires a reference to virDomainPtr only once and then uses that for subsequent >> call. This is a problem because both virDomainPtr object and virDomainObjPtr >> objects contains a domid but only the latter gets updated. >> >> So both, creating a new guest (which must be a define step and then use the >> handle to start the guest) as well as rebooting a guest cause problems for >> virt-manager. Mainly because of libxlDomainGetInfo() which retrieves the >> virDomainObjPtr for a given virDommainPtr. Then checks the domain object to be >> active or not but uses the domid from the domain to call into libxl: >> >> if (!(vm = libxlDomObjFromDomain(dom))) >> goto cleanup; >> ... >> if (!virDomainObjIsActive(vm)) { >> info->cpuTime = 0; >> info->memory = vm->def->mem.cur_balloon; >> info->maxMem = vm->def->mem.max_balloon; >> } else { >> if (libxl_domain_info(priv->ctx, &d_info, dom->id) != 0) { >> >> This fails either with dom->id being -1 (still) or using the old id from before >> the reboot. A dirty hack seems to avoid this: > > Yep, this is a pretty commonly hit problem. The solution is to *never* > access dom->id in the driver code at all. eg In this code snippet above > you could use vm->def->id instead which should be up to date. OK, it just seems for something that should not be done, it is done plenty of times in the libxl_driver codebase right now. At least pause and unpause seem to do the same...