xen: add backend driver support

Impact: backend device support

Add the basic machinery to support backend drivers.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
[corresponds to 79727b851bac in git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/Kconfig

@@ -29,6 +29,14 @@ config XEN_DEV_EVTCHN
 	  firing.
 	  If in doubt, say yes.
 
+config XEN_BACKEND
+	tristate "Backend driver support"
+	depends on XEN_DOM0
+	default y
+	help
+	  Support for backend device drivers that provide I/O services
+	  to other virtual machines.
+
 config XENFS
 	tristate "Xen filesystem"
 	default y

drivers/xen/xenbus/Makefile

@@ -6,4 +6,7 @@ xenbus-objs += xenbus_comms.o
 xenbus-objs += xenbus_xs.o
 xenbus-objs += xenbus_probe.o
 
+xenbus-be-objs-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
+xenbus-objs += $(xenbus-be-objs-y)
+
 obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o

drivers/xen/xenbus/xenbus_comms.c

@@ -49,6 +49,7 @@ static DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
 static irqreturn_t wake_waiting(int irq, void *unused)
 {
 	if (unlikely(xenstored_ready == 0)) {
+		printk(KERN_CRIT "xenbus_probe wake_waiting\n");
 		xenstored_ready = 1;
 		schedule_work(&probe_work);
 	}

drivers/xen/xenbus/xenbus_probe.c

@@ -95,17 +95,6 @@ int xenbus_match(struct device *_dev, struct device_driver *_drv)
 EXPORT_SYMBOL_GPL(xenbus_match);
 
 
-int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env)
-{
-	struct xenbus_device *dev = to_xenbus_device(_dev);
-
-	if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
-		return -ENOMEM;
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(xenbus_uevent);
-
 static void free_otherend_details(struct xenbus_device *dev)
 {
 	kfree(dev->otherend);
@@ -690,6 +679,8 @@ void xenbus_probe(struct work_struct *unused)
 {
 	xenstored_ready = 1;
 
+	printk(KERN_CRIT "xenbus_probe wake_waiting\n");
+
 	/* Notify others that xenstore is up */
 	blocking_notifier_call_chain(&xenstore_chain, 0, NULL);
 }

drivers/xen/xenbus/xenbus_probe.h

@@ -60,7 +60,6 @@ extern int xenbus_probe_devices(struct xen_bus_type *bus);
 
 extern void xenbus_dev_changed(const char *node, struct xen_bus_type *bus);
 
-extern int xenbus_uevent(struct device *_dev, struct kobj_uevent_env *env);
 extern void xenbus_dev_shutdown(struct device *_dev);
 
 extern int xenbus_dev_suspend(struct device *dev, pm_message_t state);

drivers/xen/xenbus/xenbus_probe_backend.c

@@ -0,0 +1,300 @@
+/******************************************************************************
+ * Talks to Xen Store to figure out what devices we have (backend half).
+ *
+ * Copyright (C) 2005 Rusty Russell, IBM Corporation
+ * Copyright (C) 2005 Mike Wray, Hewlett-Packard
+ * Copyright (C) 2005, 2006 XenSource Ltd
+ * Copyright (C) 2007 Solarflare Communications, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#define DPRINTK(fmt, args...)				\
+	pr_debug("xenbus_probe (%s:%d) " fmt ".\n",	\
+		 __func__, __LINE__, ##args)
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/fcntl.h>
+#include <linux/mm.h>
+#include <linux/notifier.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/hypervisor.h>
+#include <xen/xenbus.h>
+#include <xen/evtchn.h>
+#include <xen/features.h>
+
+#include "xenbus_comms.h"
+#include "xenbus_probe.h"
+
+/* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
+static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
+{
+	int domid, err;
+	const char *devid, *type, *frontend;
+	unsigned int typelen;
+
+	type = strchr(nodename, '/');
+	if (!type)
+		return -EINVAL;
+	type++;
+	typelen = strcspn(type, "/");
+	if (!typelen || type[typelen] != '/')
+		return -EINVAL;
+
+	devid = strrchr(nodename, '/') + 1;
+
+	err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
+			    "frontend", NULL, &frontend,
+			    NULL);
+	if (err)
+		return err;
+	if (strlen(frontend) == 0)
+		err = -ERANGE;
+	if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
+		err = -ENOENT;
+	kfree(frontend);
+
+	if (err)
+		return err;
+
+	if (snprintf(bus_id, XEN_BUS_ID_SIZE,
+		     "%.*s-%i-%s", typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
+		return -ENOSPC;
+	return 0;
+}
+
+static int xenbus_uevent_backend(struct device *dev,
+				 struct kobj_uevent_env *env)
+{
+	struct xenbus_device *xdev;
+	struct xenbus_driver *drv;
+	struct xen_bus_type *bus;
+
+	DPRINTK("");
+
+	if (dev == NULL)
+		return -ENODEV;
+
+	xdev = to_xenbus_device(dev);
+	bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);
+	if (xdev == NULL)
+		return -ENODEV;
+
+	/* stuff we want to pass to /sbin/hotplug */
+	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
+		return -ENOMEM;
+
+	if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
+		return -ENOMEM;
+
+	if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
+		return -ENOMEM;
+
+	if (dev->driver) {
+		drv = to_xenbus_driver(dev->driver);
+		if (drv && drv->uevent)
+			return drv->uevent(xdev, env);
+	}
+
+	return 0;
+}
+
+/* backend/<typename>/<frontend-uuid>/<name> */
+static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
+				     const char *dir,
+				     const char *type,
+				     const char *name)
+{
+	char *nodename;
+	int err;
+
+	nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
+	if (!nodename)
+		return -ENOMEM;
+
+	DPRINTK("%s\n", nodename);
+
+	err = xenbus_probe_node(bus, type, nodename);
+	kfree(nodename);
+	return err;
+}
+
+/* backend/<typename>/<frontend-domid> */
+static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type, const char *domid)
+{
+	char *nodename;
+	int err = 0;
+	char **dir;
+	unsigned int i, dir_n = 0;
+
+	DPRINTK("");
+
+	nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
+	if (!nodename)
+		return -ENOMEM;
+
+	dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
+	if (IS_ERR(dir)) {
+		kfree(nodename);
+		return PTR_ERR(dir);
+	}
+
+	for (i = 0; i < dir_n; i++) {
+		err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
+		if (err)
+			break;
+	}
+	kfree(dir);
+	kfree(nodename);
+	return err;
+}
+
+static void frontend_changed(struct xenbus_watch *watch,
+			    const char **vec, unsigned int len)
+{
+	xenbus_otherend_changed(watch, vec, len, 0);
+}
+
+static struct device_attribute xenbus_backend_dev_attrs[] = {
+	__ATTR_NULL
+};
+
+static struct xen_bus_type xenbus_backend = {
+	.root = "backend",
+	.levels = 3, 		/* backend/type/<frontend>/<id> */
+	.get_bus_id = backend_bus_id,
+	.probe = xenbus_probe_backend,
+	.otherend_changed = frontend_changed,
+	.bus = {
+		.name      = "xen-backend",
+		.match     = xenbus_match,
+		.uevent    = xenbus_uevent_backend,
+		.probe     = xenbus_dev_probe,
+		.remove    = xenbus_dev_remove,
+		.shutdown  = xenbus_dev_shutdown,
+		.dev_attrs = xenbus_backend_dev_attrs,
+	},
+};
+
+static void backend_changed(struct xenbus_watch *watch,
+			    const char **vec, unsigned int len)
+{
+	DPRINTK("");
+
+	xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_backend);
+}
+
+static struct xenbus_watch be_watch = {
+	.node = "backend",
+	.callback = backend_changed,
+};
+
+static int read_frontend_details(struct xenbus_device *xendev)
+{
+	return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
+}
+
+//void xenbus_backend_suspend(int (*fn)(struct device *, void *))
+//{
+//	DPRINTK("");
+//	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, fn);
+//}
+
+//void xenbus_backend_resume(int (*fn)(struct device *, void *))
+//{
+//	DPRINTK("");
+//	bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, fn);
+//}
+
+//int xenbus_for_each_backend(void *arg, int (*fn)(struct device *, void *))
+//{
+//	return bus_for_each_dev(&xenbus_backend.bus, NULL, arg, fn);
+//}
+//EXPORT_SYMBOL_GPL(xenbus_for_each_backend);
+
+int xenbus_dev_is_online(struct xenbus_device *dev)
+{
+	int rc, val;
+
+	rc = xenbus_scanf(XBT_NIL, dev->nodename, "online", "%d", &val);
+	if (rc != 1)
+		val = 0; /* no online node present */
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_is_online);
+
+int __xenbus_register_backend(struct xenbus_driver *drv,
+			      struct module *owner, const char *mod_name)
+{
+	drv->read_otherend_details = read_frontend_details;
+
+	return xenbus_register_driver_common(drv, &xenbus_backend,
+					     owner, mod_name);
+}
+EXPORT_SYMBOL_GPL(__xenbus_register_backend);
+
+static int backend_probe_and_watch(struct notifier_block *notifier,
+				   unsigned long event,
+				   void *data)
+{
+	/* Enumerate devices in xenstore and watch for changes. */
+	xenbus_probe_devices(&xenbus_backend);
+	printk(KERN_CRIT "%s devices probed ok\n", __func__);
+	register_xenbus_watch(&be_watch);
+	printk(KERN_CRIT "%s watch add ok ok\n", __func__);
+	printk(KERN_CRIT "%s all done\n", __func__);
+	return NOTIFY_DONE;
+}
+
+static int __init xenbus_probe_backend_init(void)
+{
+	static struct notifier_block xenstore_notifier = {
+		.notifier_call = backend_probe_and_watch
+	};
+	int err;
+
+	DPRINTK("");
+
+	/* Register ourselves with the kernel bus subsystem */
+	err = bus_register(&xenbus_backend.bus);
+	if (err) {
+		printk(KERN_CRIT "%s didn't register bus!\n", __func__);
+		return err;
+	}
+	printk(KERN_CRIT "%s bus registered ok\n", __func__);
+
+	register_xenstore_notifier(&xenstore_notifier);
+
+	return 0;
+}
+
+module_init(xenbus_probe_backend_init);

drivers/xen/xenbus/xenbus_probe_frontend.c

@@ -62,6 +62,17 @@ static int xenbus_probe_frontend(struct xen_bus_type *bus, const char *type, con
 	return err;
 }
 
+static int xenbus_uevent_frontend(struct device *_dev, struct kobj_uevent_env *env)
+{
+	struct xenbus_device *dev = to_xenbus_device(_dev);
+
+	if (add_uevent_var(env, "MODALIAS=xen:%s", dev->devicetype))
+		return -ENOMEM;
+
+	return 0;
+}
+
+
 static void backend_changed(struct xenbus_watch *watch,
 			    const char **vec, unsigned int len)
 {
@@ -81,7 +92,7 @@ static struct xen_bus_type xenbus_frontend = {
 	.bus = {
 		.name     = "xen",
 		.match    = xenbus_match,
-		.uevent   = xenbus_uevent,
+		.uevent   = xenbus_uevent_frontend,
 		.probe    = xenbus_dev_probe,
 		.remove   = xenbus_dev_remove,
 		.shutdown = xenbus_dev_shutdown,
@@ -232,8 +243,25 @@ int __xenbus_register_frontend(struct xenbus_driver *drv,
 }
 EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
 
+static int frontend_probe_and_watch(struct notifier_block *notifier,
+				   unsigned long event,
+				   void *data)
+{
+	/* Enumerate devices in xenstore and watch for changes. */
+	xenbus_probe_devices(&xenbus_frontend);
+	printk(KERN_CRIT "%s devices probed ok\n", __func__);
+	register_xenbus_watch(&fe_watch);
+	printk(KERN_CRIT "%s watch add ok ok\n", __func__);
+	printk(KERN_CRIT "%s all done\n", __func__);
+	return NOTIFY_DONE;
+}
+
+
 static int __init xenbus_probe_frontend_init(void)
 {
+	static struct notifier_block xenstore_notifier = {
+		.notifier_call = frontend_probe_and_watch
+	};
 	int err;
 
 	DPRINTK("");
@@ -246,14 +274,7 @@ static int __init xenbus_probe_frontend_init(void)
 	}
 	printk(KERN_CRIT "%s bus registered ok\n", __func__);
 
-	if (!xen_initial_domain()) {
-		/* Enumerate devices in xenstore and watch for changes. */
-		xenbus_probe_devices(&xenbus_frontend);
-		printk(KERN_CRIT "%s devices probed ok\n", __func__);
-		register_xenbus_watch(&fe_watch);
-		printk(KERN_CRIT "%s watch add ok ok\n", __func__);
-		printk(KERN_CRIT "%s all done\n", __func__);
-	}
+	register_xenstore_notifier(&xenstore_notifier);
 
 	return 0;
 }

include/xen/xenbus.h

@@ -94,7 +94,7 @@ struct xenbus_driver {
 	int (*remove)(struct xenbus_device *dev);
 	int (*suspend)(struct xenbus_device *dev, pm_message_t state);
 	int (*resume)(struct xenbus_device *dev);
-	int (*uevent)(struct xenbus_device *, char **, int, char *, int);
+	int (*uevent)(struct xenbus_device *, struct kobj_uevent_env *);
 	struct device_driver driver;
 	int (*read_otherend_details)(struct xenbus_device *dev);
 	int (*is_ready)(struct xenbus_device *dev);