Re: [libvirt] [PATCH] docs: formatdomain: explain host-model/host-passthrough requirements

* Paolo Bonzini (pbonzini(a)redhat.com) wrote: > host-passthrough documentation menions that the source and destination > hosts are not identical in both hardware and configuration. Configuration > actually includes microcode version and QEMU version, but this is not > clear so make it explicit > > Signed-off-by: Paolo Bonzini <pbonzini(a)redhat.com&gt; > --- > docs/formatdomain.html.in | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in > index f5c882141a..6d084d7c04 100644 > --- a/docs/formatdomain.html.in > +++ b/docs/formatdomain.html.in > @@ -1590,8 +1590,8 @@ > hand, the ABI provided to the guest is reproducible. During > migration, complete CPU model definition is transferred to the > destination host so the migrated guest will see exactly the same CPU > - model even if the destination host contains more capable CPUs for > - the running instance of the guest; but shutting down and restarting > + model for the running instance of the guest, even if the destination > + host contains more capable CPUs or newer kernel; but shutting down and restarting > the guest may present different hardware to the guest according to > the capabilities of the new host. Prior to libvirt 3.2.0 and QEMU > 2.9.0 detection of the host CPU model via QEMU is not supported. > @@ -1625,10 +1625,10 @@ > environment cannot be reproduced on different hardware. Thus, if you > hit any bugs, you are on your own. Further details of that CPU can > be changed using <code>feature</code> elements. Migration of a guest > - using host-passthrough is dangerous if the source and destination > - hosts are not identical in both hardware and configuration. If such > - a migration is attempted then the guest may hang or crash upon > - resuming execution on the destination host.</dd> > + using host-passthrough is dangerous if the source and destination hosts > + are not identical in both hardware, QEMU version, microcode version > + and configuration. If such a migration is attempted then the guest may > + hang or crash upon resuming execution on the destination host.</dd> If libvirt is driving qemu with 'exact' on the cpu option, under what situation would it hang/crash on the destination? All of the microcode changes I think have caused a flag to appear, and thus it would be required on the destination. Dave > </dl> > > Both <code>host-model</code> and <code>host-passthrough</code> modes > -- > 2.21.0 > -- Dr. David Alan Gilbert / dgilbert(a)redhat.com / Manchester, UK