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

[Eric Blake]

On 10/18/2013 08:08 AM, Jiri Denemark wrote:
> 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 at redhat.com>
> ---
>  docs/formatdomain.html.in | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)

ACK.  Never hurts to document caveats.

> 
> 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
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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