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

On Tue, Mar 25, 2014 at 04:42:25PM +0100, Stefan Bader wrote: > 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... I expect those pretty much all need to be fixed

Regards, Daniel