|Summary:||RFE: default to cpu host-model (when it's ready)|
|Product:||[Community] Virtualization Tools||Reporter:||Cole Robinson <crobinso>|
|Component:||virt-manager||Assignee:||Cole Robinson <crobinso>|
|Status:||CLOSED UPSTREAM||QA Contact:|
|Version:||unspecified||CC:||awilliam, berrange, crobinso, desintegr, ehabkost, fche, gscrivan, ibaldo, martin, pvalena, redhat-bugzilla|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2018-10-04 18:46:36 UTC||Type:||Bug|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Cole Robinson 2014-01-17 22:51:10 UTC
Eventually I think we should default to cpu mode=host-model for new VMs, or at least provide the option. Upstream now has a 'default CPU' section in the preferences dialog, but it's only doing 'copy host cpu' and not host-model at the moment. Reason being, host-model implementation has known issues: host-model doesn't match reality, can cause guest panics: https://bugzilla.redhat.com/show_bug.cgi?id=870071 host-model persistence: https://bugzilla.redhat.com/show_bug.cgi?id=1054935 RHEL bugs about the steps needed to get to a proper working order: libvirt: host-model avx crash: https://bugzilla.redhat.com/show_bug.cgi?id=1014682 libvirt: query qemu: https://bugzilla.redhat.com/show_bug.cgi?id=824989 qemu: CPU probe interface: https://bugzilla.redhat.com/show_bug.cgi?id=824987 libvirt: use -cpu enforce: https://bugzilla.redhat.com/show_bug.cgi?id=822148 And some misc libvirt bugs that come into play for virt-manager: cpu map API support: https://bugzilla.redhat.com/show_bug.cgi?id=916786 cpu model checking busted for tcg: https://bugzilla.redhat.com/show_bug.cgi?id=1002066 So basically, we need to wait for a lot of that to be solved before we can safely change the default.
Comment 1 Frank Ch. Eigler 2015-05-06 17:01:41 UTC
Would this be a good place to ask that virt-manager's preferences permit "host-passthrough" as a valid option for cpu-model?
Comment 2 Cole Robinson 2015-05-06 17:08:40 UTC
You can type 'host-passthrough' into the UI box and virt-manager will do the right thing. However host-passthrough has certain supportability issues with libvirt, so we don't expose it as a proper option in the UI
Comment 3 Pavel Valena 2016-11-22 17:48:31 UTC
Hello, what is the status on this? Also, is 'host-passthrough' safe with libvirt now?
Comment 4 Cole Robinson 2017-07-10 23:47:47 UTC
*** Bug 1468016 has been marked as a duplicate of this bug. ***
Comment 5 Eduardo Habkost 2017-07-10 23:58:52 UTC
(In reply to Pavel Valena from comment #3) > Hello, what is the status on this? > > Also, is 'host-passthrough' safe with libvirt now? (Replying 8 months later) I consider host-passthrough/"-cpu host" safe today, but it will prevent live-migration. If live-migration is not required, it is the best way to make of use all features supported by the host CPU + hypervisor. "host-model" is now supposed to be safe (at least the bugs mentioned in comment #0 are all fixed now).
Comment 6 Pavel Valena 2017-07-11 22:09:22 UTC
Thanks for information!
Comment 7 Cole Robinson 2018-10-04 18:46:36 UTC
If libvirt/qemu combo is new enough, we use host-model as the default now: commit 469fed08a04777d72cbb73e1dc948cffe31f7858 Author: Cole Robinson <email@example.com> Date: Thu Oct 4 12:23:32 2018 -0400 guest: Default to cpu mode=host-model if libvirt is new enough