On 09/24/2013 02:49 AM, Hu Tao wrote: > 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. > Yeah I think that's what Jiri was proposing. > 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. > I think it was meant to be a libvirt approximation of -cpu host, but unfortunately the current implementation is less complete than -cpu host but has some of the same problems. Maybe _all_ of the same problems, but I'd have to look to see if libvirt does something special WRT host-model and migration. - Cole _______________________________________________ virt-tools-list mailing list virt-tools-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/virt-tools-list
