On Mon, Sep 23, 2013 at 02:30:53PM -0400, Cole Robinson wrote: > On 09/23/2013 07:17 AM, Hu Tao wrote: > > On Tue, Apr 23, 2013 at 05:20:12PM +0200, Jiri Denemark wrote: > >> On Tue, Apr 23, 2013 at 10:47:58 -0400, Cole Robinson wrote: > >>> On 04/23/2013 08:06 AM, Martin Kletzander wrote: > >>>> On 04/23/2013 01:56 PM, Guannan Ren wrote: > >>>>> On 04/23/2013 07:37 PM, Martin Kletzander wrote: > >>>>>> On 04/20/2013 10:09 PM, Cole Robinson wrote: > >>>>>>> On 04/18/2013 03:47 AM, Guannan Ren wrote: > >>>>>>>> v1 to v2: > >>>>>>>> removed UPDATE_CPU flag checking > >>>>>>>> renamed helper function name from reset() to clear_attrs() > >>>>>>>> change the check box to be labeled 'Use host CPU model' > >>>>>>>> remove the lightbulb icon, use tooltip instead > >>>>>>>> reword the tooltip from Cole's > >>>>>>>> remove the WARN image icon from UI > >>>>>>>> > >>>>>>>> Add a checkbox for 'host-model' mode and removed 'Copy host CPU > >>>>>>>> configuration' > >>>>>>>> button. > >>>>>>>> > >>>>>> Sorry for not catching this thread earlier, but IIUC, the 'host-model' > >>>>>> doesn't make up for the button. XML is saved with 'host-model' then, > >>>>>> right? > >>>>>> > >>>>>> Unfortunately, I can't see that easily right now as git virt-manager > >>>>>> consistently crashes for me on all VMs and bare metal as well and I made > >>>>>> that one of my priorities in order to speed up the bug hunt on it. > >>>>>> > >>>>> > >>>>> Martin, I am using virt-manager git head now, it seems fine for me. > >>>>> Is there anything wrong about 'host-model', I can't quite follow you > >>>>> here. > >>>>> > >>>>> Guannan > >>>>> > >>>> > >>>> I was just wondering if dropping the button isn't a bad idea, some guest > >>>> OS might have problems when it is ran on different CPU, which is what > >>>> might happen with host-model after destroy/start, but would be avoided > >>>> with 'Copy host configuration'. I'm not saying 'host-model' is wrong, > >>>> we definitely want the support for that. > >>>> > >>> > >>> Hmm, how would host-model change CPU between destroy/start... like a libvirt > >>> update supporting more flags? I didn't think about that, and it is > >>> problematic. Libvirt goes to great lengths to try and preserve hardware config > >>> for a VM across libvirt updates, host-model potentially throws that out the > >>> window... > >>> > >>> Unless there's some clever way of getting around that it makes me think > >>> host-model just doesn't fit in the UI. Trying to explain all the nuances of > >>> this stuff in the current UI is impossible, so until we come up with something > >>> different we should go with the safest bet, which is only providing the old > >>> button press behavior. > >> > >> I agree that currently copying host CPU XML into guest CPU is safest > >> than using host-model (which is just a shortcut for it but the config is > >> not preserved after domain shutdown). However, host-model will be > >> improved (hopefully soon) to provide more. And I think we (libvirt) > >> should come up with something that would preserve the configuration, > >> too. > > > > If we preserve cpu configurations when host-model is specified, what to > > do with situations where the preserved configurations are different with > > what host-model gets? > > > > - VM is copied to another host with a different cpu. The new cpu may > > have all features in preserved configurations, or may not. Using > > preserved configurations may fail to start VM. > > > > - VM is migrated to another host with a different cpu. Same as above. > > > > Yes, without host-model handling those bits for us, virt-manager would need to > explicitly handle it. Thankfully libvirt already has APIs that could help us > here. But really I'm less concerned with cross host, non-uniform hardware > migration compatibility than I am with a libvirt upgrade implicitly changing > guest hardware. > > > - libvirt is updated to support more flags. It's better to update the > > preserved configuration. > > > > If libvirt supports more flags, we update libvirt, restart VM, guest sees the > CPU is different... wouldn't this cause Windows reactivation? Not tested. But the main concern is that guest should not be affected by changes caused by host-model during migration, libvirt update, etc., right? It seems that we have only one option left, use preserved configuration in such cases, which effectively makes host-model a one-time definition and turns it into custom mode at the first time, which is almost like the ``copy host CPU configuration'' button, which is already there. I'm wondering the purpose of host-model when it was firstly introduced. Handling preserved configuration in libvirt will probably make host-model a different thing, thus brings compatibility issues. _______________________________________________ virt-tools-list mailing list virt-tools-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/virt-tools-list
