Re: [libvirt] [RFC] docs: Discourage usage of cache mode=passthrough

On 09/19/2017 03:37 PM, Eduardo Habkost wrote: > Cache mode=passthrough can result in a broken cache topology if > the domain topology is not exactly the same as the host topology. > Warn about that in the documentation. > > Bug report for reference: > https://bugzilla.redhat.com/show_bug.cgi?id=1184125 > > Signed-off-by: Eduardo Habkost <ehabkost(a)redhat.com&gt; > --- > docs/formatdomain.html.in | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in > index 57ec2ff34..9c21892f3 100644 > --- a/docs/formatdomain.html.in > +++ b/docs/formatdomain.html.in > @@ -1478,7 +1478,9 @@ > > <dt><code>passthrough</code></dt> > <dd>The real CPU cache data reported by the host CPU will be > - passed through to the virtual CPU.</dd> > + passed through to the virtual CPU. Using this mode is not > + recommended unless the domain CPU and NUMA topology is exactly > + the same as the host CPU and NUMA topology.</dd> To me this sounds like it should be forbidden by libvirt, rather than just documented as "bad". (I haven't followed any previous discussion on the topic though, so maybe I'm over-reacting).