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>

3 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2c85c0692b01..8bbe83b9d0b2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2631,6 +2631,7 @@ and is between 256 and 4096 characters. It is defined in the file
                         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:
diff --git a/arch/x86/xen/platform-pci-unplug.c b/arch/x86/xen/platform-pci-unplug.c
index 554c002a1e1a..070dfa0654bd 100644
--- a/arch/x86/xen/platform-pci-unplug.c
+++ b/arch/x86/xen/platform-pci-unplug.c
@@ -72,6 +72,9 @@ void __init xen_unplug_emulated_devices(void)
 {
         int r;
 
+        /* user explicitly requested no unplug */
+        if (xen_emul_unplug & XEN_UNPLUG_NEVER)
+                return;
         /* check the version of the xen platform PCI device */
         r = check_platform_magic();
         /* If the version matches enable the Xen platform PCI driver.
@@ -127,6 +130,8 @@ static int __init parse_xen_emul_unplug(char *arg)
                         xen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
                 else if (!strncmp(p, "ignore", l))
                         xen_emul_unplug |= XEN_UNPLUG_IGNORE;
+                else if (!strncmp(p, "never", l))
+                        xen_emul_unplug |= XEN_UNPLUG_NEVER;
                 else
                         printk(KERN_WARNING "unrecognised option '%s' "
                                  "in parameter 'xen_emul_unplug'\n", p);
diff --git a/include/xen/platform_pci.h b/include/xen/platform_pci.h
index ce9d671c636c..123b7752fa6a 100644
--- a/include/xen/platform_pci.h
+++ b/include/xen/platform_pci.h
@@ -21,6 +21,7 @@
 #define XEN_UNPLUG_AUX_IDE_DISKS 4
 #define XEN_UNPLUG_ALL 7
 #define XEN_UNPLUG_IGNORE 8
+#define XEN_UNPLUG_NEVER 16
 
 static inline int xen_must_unplug_nics(void) {
 #if (defined(CONFIG_XEN_NETDEV_FRONTEND) || \