xen: pvhvm: allow user to request no emulated device unplug

this allows the user to disable pvhvm and revert to emulated devices
in case of a system misconfiguration (e.g. initramfs with only
emulated drivers in it).

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2c85c06..8bbe83b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2631,6 +2631,7 @@
 			all -- unplug all emulated devices (NICs and IDE disks)
 			ignore -- continue loading the Xen platform PCI driver even
 				if the version check failed
+			never -- do not unplug even if version check succeeds
 
 	xirc2ps_cs=	[NET,PCMCIA]
 			Format: