xen: pvhvm: rename xen_emul_unplug=ignore to =unnnecessary

It is not immediately clear what this option causes to become
ignored. The actual meaning is that it is not necessary to unplug the
emulated devices to safely use the PV ones, even if the platform does
not support the unplug protocol. (pressumably the user will only add
this option if they have ensured that their domain configuration is
safe).

I think xen_emul_unplug=unnecessary better captures this.
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>

Documentation/kernel-parameters.txt

@@ -2629,8 +2629,9 @@ and is between 256 and 4096 characters. It is defined in the file
 			aux-ide-disks -- unplug non-primary-master IDE devices
 			nics -- unplug network devices
 			all -- unplug all emulated devices (NICs and IDE disks)
-			ignore -- continue loading the Xen platform PCI driver even
-				if the version check failed
+			unnecessary -- unplugging emulated devices is
+				unnecessary even if the host did not respond to
+				the unplug protocol
 			never -- do not unplug even if version check succeeds
 
 	xirc2ps_cs=	[NET,PCMCIA]

arch/x86/xen/platform-pci-unplug.c

@@ -78,10 +78,11 @@ void __init xen_unplug_emulated_devices(void)
 	/* check the version of the xen platform PCI device */
 	r = check_platform_magic();
 	/* If the version matches enable the Xen platform PCI driver.
-	 * Also enable the Xen platform PCI driver if the version is really old
-	 * and the user told us to ignore it. */
+	 * Also enable the Xen platform PCI driver if the host does
+	 * not support the unplug protocol (XEN_PLATFORM_ERR_MAGIC)
+	 * but the user told us that unplugging is unnecessary. */
 	if (r && !(r == XEN_PLATFORM_ERR_MAGIC &&
-			(xen_emul_unplug & XEN_UNPLUG_IGNORE)))
+			(xen_emul_unplug & XEN_UNPLUG_UNNECESSARY)))
 		return;
 	/* Set the default value of xen_emul_unplug depending on whether or
 	 * not the Xen PV frontends and the Xen platform PCI driver have
@@ -102,7 +103,7 @@ void __init xen_unplug_emulated_devices(void)
 		}
 	}
 	/* Now unplug the emulated devices */
-	if (!(xen_emul_unplug & XEN_UNPLUG_IGNORE))
+	if (!(xen_emul_unplug & XEN_UNPLUG_UNNECESSARY))
 		outw(xen_emul_unplug, XEN_IOPORT_UNPLUG);
 	xen_platform_pci_unplug = xen_emul_unplug;
 }
@@ -128,8 +129,8 @@ static int __init parse_xen_emul_unplug(char *arg)
 			xen_emul_unplug |= XEN_UNPLUG_AUX_IDE_DISKS;
 		else if (!strncmp(p, "nics", l))
 			xen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
-		else if (!strncmp(p, "ignore", l))
-			xen_emul_unplug |= XEN_UNPLUG_IGNORE;
+		else if (!strncmp(p, "unnecessary", l))
+			xen_emul_unplug |= XEN_UNPLUG_UNNECESSARY;
 		else if (!strncmp(p, "never", l))
 			xen_emul_unplug |= XEN_UNPLUG_NEVER;
 		else

drivers/block/xen-blkfront.c

@@ -834,7 +834,7 @@ static int blkfront_probe(struct xenbus_device *dev,
 		char *type;
 		int len;
 		/* no unplug has been done: do not hook devices != xen vbds */
-		if (xen_platform_pci_unplug & XEN_UNPLUG_IGNORE) {
+		if (xen_platform_pci_unplug & XEN_UNPLUG_UNNECESSARY) {
 			int major;
 
 			if (!VDEV_IS_EXTENDED(vdevice))

include/xen/platform_pci.h

@@ -20,7 +20,7 @@
 #define XEN_UNPLUG_ALL_NICS 2
 #define XEN_UNPLUG_AUX_IDE_DISKS 4
 #define XEN_UNPLUG_ALL 7
-#define XEN_UNPLUG_IGNORE 8
+#define XEN_UNPLUG_UNNECESSARY 8
 #define XEN_UNPLUG_NEVER 16
 
 static inline int xen_must_unplug_nics(void) {