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

[Eduardo Habkost]

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 at 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>
 
               <dt><code>disable</code></dt>
               <dd>The virtual CPU will report no CPU cache of the specified
-- 
2.13.5