* Paolo Bonzini (pbonzini@xxxxxxxxxx) wrote: > Unlike host-model, host-passthrough does not do any check, it just passes > "-cpu host" blindly. Therefore, lack of flags can and will result in > crashes---SIGSEGV if it happens in userspace, but worse if for example the > destination doesn't have an MSR that should be there according to the > kernel. Ah OK, yes. Dave > Paolo > > Il mar 6 ago 2019, 18:22 Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> ha > scritto: > > > * Paolo Bonzini (pbonzini@xxxxxxxxxx) 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@xxxxxxxxxx> > > > --- > > > 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@xxxxxxxxxx / Manchester, UK > > -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
