Re: [libvirt] [PATCH] docs: Expand description of host-model CPU mode

host-model is a nice idea but it's current implementation make it useless on some hosts so it should be used with care. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; --- docs/formatdomain.html.in | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index c5a3fa8..491a6a9 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -924,7 +924,16 @@ model even if the destination host contains more capable CPUs for the running instance of the guest; but shutting down and restarting the guest may present different hardware to the guest according to - the capabilities of the new host.</dd> + the capabilities of the new host. <strong>Beware</strong>, due to the + way libvirt detects host CPU and due to the fact libvirt does not + talk to QEMU/KVM when creating the CPU model, CPU configuration + created using <code>host-model</code> may not work as expected. The + guest CPU may differ from the configuration and it may also confuse + guest OS by using a combination of CPU features and other parameters + (such as CPUID level) that don't work. Until these issues are fixed, + it's a good idea to avoid using <code>host-model</code> and use + <code>custom</code> mode with just the CPU model from host + capabilities XML.</dd> <dt><code>host-passthrough</code></dt> <dd>With this mode, the CPU visible to the guest should be exactly the same as the host CPU even in the aspects that libvirt does not