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>
---
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).