xen: add the Xenbus sysfs and virtual device hotplug driver

This communicates with the machine control software via a registry
residing in a controlling virtual machine. This allows dynamic
creation, destruction and modification of virtual device
configurations (network devices, block devices and CPUS, to name some
examples).

[ Greg, would you mind giving this a review?  Thanks -J ]

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Greg KH <greg@kroah.com>

1 files changed, 569 insertions, 0 deletions

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
new file mode 100644
index 000000000000..9fd2f70ab46d
--- /dev/null
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -0,0 +1,569 @@
+/******************************************************************************
+ * Client-facing interface for the Xenbus driver.  In other words, the
+ * interface between the Xenbus and the device-specific code, be it the
+ * frontend or the backend of that driver.
+ *
+ * Copyright (C) 2005 XenSource Ltd
+ *
+ * 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.
+ */
+
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/event_channel.h>
+#include <xen/events.h>
+#include <xen/grant_table.h>
+#include <xen/xenbus.h>
+
+const char *xenbus_strstate(enum xenbus_state state)
+{
+        static const char *const name[] = {
+                [ XenbusStateUnknown      ] = "Unknown",
+                [ XenbusStateInitialising ] = "Initialising",
+                [ XenbusStateInitWait     ] = "InitWait",
+                [ XenbusStateInitialised  ] = "Initialised",
+                [ XenbusStateConnected    ] = "Connected",
+                [ XenbusStateClosing      ] = "Closing",
+                [ XenbusStateClosed       ] = "Closed",
+        };
+        return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
+}
+EXPORT_SYMBOL_GPL(xenbus_strstate);
+
+/**
+ * xenbus_watch_path - register a watch
+ * @dev: xenbus device
+ * @path: path to watch
+ * @watch: watch to register
+ * @callback: callback to register
+ *
+ * Register a @watch on the given path, using the given xenbus_watch structure
+ * for storage, and the given @callback function as the callback.  Return 0 on
+ * success, or -errno on error.  On success, the given @path will be saved as
+ * @watch->node, and remains the caller's to free.  On error, @watch->node will
+ * be NULL, the device will switch to %XenbusStateClosing, and the error will
+ * be saved in the store.
+ */
+int xenbus_watch_path(struct xenbus_device *dev, const char *path,
+                      struct xenbus_watch *watch,
+                      void (*callback)(struct xenbus_watch *,
+                                       const char **, unsigned int))
+{
+        int err;
+
+        watch->node = path;
+        watch->callback = callback;
+
+        err = register_xenbus_watch(watch);
+
+        if (err) {
+                watch->node = NULL;
+                watch->callback = NULL;
+                xenbus_dev_fatal(dev, err, "adding watch on %s", path);
+        }
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_watch_path);
+
+
+/**
+ * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path
+ * @dev: xenbus device
+ * @watch: watch to register
+ * @callback: callback to register
+ * @pathfmt: format of path to watch
+ *
+ * Register a watch on the given @path, using the given xenbus_watch
+ * structure for storage, and the given @callback function as the callback.
+ * Return 0 on success, or -errno on error.  On success, the watched path
+ * (@path/@path2) will be saved as @watch->node, and becomes the caller's to
+ * kfree().  On error, watch->node will be NULL, so the caller has nothing to
+ * free, the device will switch to %XenbusStateClosing, and the error will be
+ * saved in the store.
+ */
+int xenbus_watch_pathfmt(struct xenbus_device *dev,
+                         struct xenbus_watch *watch,
+                         void (*callback)(struct xenbus_watch *,
+                                        const char **, unsigned int),
+                         const char *pathfmt, ...)
+{
+        int err;
+        va_list ap;
+        char *path;
+
+        va_start(ap, pathfmt);
+        path = kvasprintf(GFP_KERNEL, pathfmt, ap);
+        va_end(ap);
+
+        if (!path) {
+                xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch");
+                return -ENOMEM;
+        }
+        err = xenbus_watch_path(dev, path, watch, callback);
+
+        if (err)
+                kfree(path);
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt);
+
+
+/**
+ * xenbus_switch_state
+ * @dev: xenbus device
+ * @xbt: transaction handle
+ * @state: new state
+ *
+ * Advertise in the store a change of the given driver to the given new_state.
+ * Return 0 on success, or -errno on error.  On error, the device will switch
+ * to XenbusStateClosing, and the error will be saved in the store.
+ */
+int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
+{
+        /* We check whether the state is currently set to the given value, and
+           if not, then the state is set.  We don't want to unconditionally
+           write the given state, because we don't want to fire watches
+           unnecessarily.  Furthermore, if the node has gone, we don't write
+           to it, as the device will be tearing down, and we don't want to
+           resurrect that directory.
+
+           Note that, because of this cached value of our state, this function
+           will not work inside a Xenstore transaction (something it was
+           trying to in the past) because dev->state would not get reset if
+           the transaction was aborted.
+
+         */
+
+        int current_state;
+        int err;
+
+        if (state == dev->state)
+                return 0;
+
+        err = xenbus_scanf(XBT_NIL, dev->nodename, "state", "%d",
+                           &current_state);
+        if (err != 1)
+                return 0;
+
+        err = xenbus_printf(XBT_NIL, dev->nodename, "state", "%d", state);
+        if (err) {
+                if (state != XenbusStateClosing) /* Avoid looping */
+                        xenbus_dev_fatal(dev, err, "writing new state");
+                return err;
+        }
+
+        dev->state = state;
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_switch_state);
+
+int xenbus_frontend_closed(struct xenbus_device *dev)
+{
+        xenbus_switch_state(dev, XenbusStateClosed);
+        complete(&dev->down);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_frontend_closed);
+
+/**
+ * Return the path to the error node for the given device, or NULL on failure.
+ * If the value returned is non-NULL, then it is the caller's to kfree.
+ */
+static char *error_path(struct xenbus_device *dev)
+{
+        return kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
+}
+
+
+static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
+                                const char *fmt, va_list ap)
+{
+        int ret;
+        unsigned int len;
+        char *printf_buffer = NULL;
+        char *path_buffer = NULL;
+
+#define PRINTF_BUFFER_SIZE 4096
+        printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
+        if (printf_buffer == NULL)
+                goto fail;
+
+        len = sprintf(printf_buffer, "%i ", -err);
+        ret = vsnprintf(printf_buffer+len, PRINTF_BUFFER_SIZE-len, fmt, ap);
+
+        BUG_ON(len + ret > PRINTF_BUFFER_SIZE-1);
+
+        dev_err(&dev->dev, "%s\n", printf_buffer);
+
+        path_buffer = error_path(dev);
+
+        if (path_buffer == NULL) {
+                dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
+                       dev->nodename, printf_buffer);
+                goto fail;
+        }
+
+        if (xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer) != 0) {
+                dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
+                       dev->nodename, printf_buffer);
+                goto fail;
+        }
+
+fail:
+        kfree(printf_buffer);
+        kfree(path_buffer);
+}
+
+
+/**
+ * xenbus_dev_error
+ * @dev: xenbus device
+ * @err: error to report
+ * @fmt: error message format
+ *
+ * Report the given negative errno into the store, along with the given
+ * formatted message.
+ */
+void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        xenbus_va_dev_error(dev, err, fmt, ap);
+        va_end(ap);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_error);
+
+/**
+ * xenbus_dev_fatal
+ * @dev: xenbus device
+ * @err: error to report
+ * @fmt: error message format
+ *
+ * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by
+ * xenbus_switch_state(dev, NULL, XenbusStateClosing) to schedule an orderly
+ * closedown of this driver and its peer.
+ */
+
+void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        xenbus_va_dev_error(dev, err, fmt, ap);
+        va_end(ap);
+
+        xenbus_switch_state(dev, XenbusStateClosing);
+}
+EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
+
+/**
+ * xenbus_grant_ring
+ * @dev: xenbus device
+ * @ring_mfn: mfn of ring to grant
+
+ * Grant access to the given @ring_mfn to the peer of the given device.  Return
+ * 0 on success, or -errno on error.  On error, the device will switch to
+ * XenbusStateClosing, and the error will be saved in the store.
+ */
+int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn)
+{
+        int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
+        if (err < 0)
+                xenbus_dev_fatal(dev, err, "granting access to ring page");
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_grant_ring);
+
+
+/**
+ * Allocate an event channel for the given xenbus_device, assigning the newly
+ * created local port to *port.  Return 0 on success, or -errno on error.  On
+ * error, the device will switch to XenbusStateClosing, and the error will be
+ * saved in the store.
+ */
+int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port)
+{
+        struct evtchn_alloc_unbound alloc_unbound;
+        int err;
+
+        alloc_unbound.dom = DOMID_SELF;
+        alloc_unbound.remote_dom = dev->otherend_id;
+
+        err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
+                                          &alloc_unbound);
+        if (err)
+                xenbus_dev_fatal(dev, err, "allocating event channel");
+        else
+                *port = alloc_unbound.port;
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
+
+
+/**
+ * Bind to an existing interdomain event channel in another domain. Returns 0
+ * on success and stores the local port in *port. On error, returns -errno,
+ * switches the device to XenbusStateClosing, and saves the error in XenStore.
+ */
+int xenbus_bind_evtchn(struct xenbus_device *dev, int remote_port, int *port)
+{
+        struct evtchn_bind_interdomain bind_interdomain;
+        int err;
+
+        bind_interdomain.remote_dom = dev->otherend_id;
+        bind_interdomain.remote_port = remote_port;
+
+        err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
+                                          &bind_interdomain);
+        if (err)
+                xenbus_dev_fatal(dev, err,
+                                 "binding to event channel %d from domain %d",
+                                 remote_port, dev->otherend_id);
+        else
+                *port = bind_interdomain.local_port;
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_bind_evtchn);
+
+
+/**
+ * Free an existing event channel. Returns 0 on success or -errno on error.
+ */
+int xenbus_free_evtchn(struct xenbus_device *dev, int port)
+{
+        struct evtchn_close close;
+        int err;
+
+        close.port = port;
+
+        err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
+        if (err)
+                xenbus_dev_error(dev, err, "freeing event channel %d", port);
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
+
+
+/**
+ * xenbus_map_ring_valloc
+ * @dev: xenbus device
+ * @gnt_ref: grant reference
+ * @vaddr: pointer to address to be filled out by mapping
+ *
+ * Based on Rusty Russell's skeleton driver's map_page.
+ * Map a page of memory into this domain from another domain's grant table.
+ * xenbus_map_ring_valloc allocates a page of virtual address space, maps the
+ * page to that address, and sets *vaddr to that address.
+ * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
+ * or -ENOMEM on error. If an error is returned, device will switch to
+ * XenbusStateClosing and the error message will be saved in XenStore.
+ */
+int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
+{
+        struct gnttab_map_grant_ref op = {
+                .flags = GNTMAP_host_map,
+                .ref   = gnt_ref,
+                .dom   = dev->otherend_id,
+        };
+        struct vm_struct *area;
+
+        *vaddr = NULL;
+
+        area = alloc_vm_area(PAGE_SIZE);
+        if (!area)
+                return -ENOMEM;
+
+        op.host_addr = (unsigned long)area->addr;
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
+                BUG();
+
+        if (op.status != GNTST_okay) {
+                free_vm_area(area);
+                xenbus_dev_fatal(dev, op.status,
+                                 "mapping in shared page %d from domain %d",
+                                 gnt_ref, dev->otherend_id);
+                return op.status;
+        }
+
+        /* Stuff the handle in an unused field */
+        area->phys_addr = (unsigned long)op.handle;
+
+        *vaddr = area->addr;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
+
+
+/**
+ * xenbus_map_ring
+ * @dev: xenbus device
+ * @gnt_ref: grant reference
+ * @handle: pointer to grant handle to be filled
+ * @vaddr: address to be mapped to
+ *
+ * Map a page of memory into this domain from another domain's grant table.
+ * xenbus_map_ring does not allocate the virtual address space (you must do
+ * this yourself!). It only maps in the page to the specified address.
+ * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
+ * or -ENOMEM on error. If an error is returned, device will switch to
+ * XenbusStateClosing and the error message will be saved in XenStore.
+ */
+int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
+                    grant_handle_t *handle, void *vaddr)
+{
+        struct gnttab_map_grant_ref op = {
+                .host_addr = (unsigned long)vaddr,
+                .flags     = GNTMAP_host_map,
+                .ref       = gnt_ref,
+                .dom       = dev->otherend_id,
+        };
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
+                BUG();
+
+        if (op.status != GNTST_okay) {
+                xenbus_dev_fatal(dev, op.status,
+                                 "mapping in shared page %d from domain %d",
+                                 gnt_ref, dev->otherend_id);
+        } else
+                *handle = op.handle;
+
+        return op.status;
+}
+EXPORT_SYMBOL_GPL(xenbus_map_ring);
+
+
+/**
+ * xenbus_unmap_ring_vfree
+ * @dev: xenbus device
+ * @vaddr: addr to unmap
+ *
+ * Based on Rusty Russell's skeleton driver's unmap_page.
+ * Unmap a page of memory in this domain that was imported from another domain.
+ * Use xenbus_unmap_ring_vfree if you mapped in your memory with
+ * xenbus_map_ring_valloc (it will free the virtual address space).
+ * Returns 0 on success and returns GNTST_* on error
+ * (see xen/include/interface/grant_table.h).
+ */
+int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
+{
+        struct vm_struct *area;
+        struct gnttab_unmap_grant_ref op = {
+                .host_addr = (unsigned long)vaddr,
+        };
+
+        /* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr)
+         * method so that we don't have to muck with vmalloc internals here.
+         * We could force the user to hang on to their struct vm_struct from
+         * xenbus_map_ring_valloc, but these 6 lines considerably simplify
+         * this API.
+         */
+        read_lock(&vmlist_lock);
+        for (area = vmlist; area != NULL; area = area->next) {
+                if (area->addr == vaddr)
+                        break;
+        }
+        read_unlock(&vmlist_lock);
+
+        if (!area) {
+                xenbus_dev_error(dev, -ENOENT,
+                                 "can't find mapped virtual address %p", vaddr);
+                return GNTST_bad_virt_addr;
+        }
+
+        op.handle = (grant_handle_t)area->phys_addr;
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
+                BUG();
+
+        if (op.status == GNTST_okay)
+                free_vm_area(area);
+        else
+                xenbus_dev_error(dev, op.status,
+                                 "unmapping page at handle %d error %d",
+                                 (int16_t)area->phys_addr, op.status);
+
+        return op.status;
+}
+EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
+
+
+/**
+ * xenbus_unmap_ring
+ * @dev: xenbus device
+ * @handle: grant handle
+ * @vaddr: addr to unmap
+ *
+ * Unmap a page of memory in this domain that was imported from another domain.
+ * Returns 0 on success and returns GNTST_* on error
+ * (see xen/include/interface/grant_table.h).
+ */
+int xenbus_unmap_ring(struct xenbus_device *dev,
+                      grant_handle_t handle, void *vaddr)
+{
+        struct gnttab_unmap_grant_ref op = {
+                .host_addr = (unsigned long)vaddr,
+                .handle    = handle,
+        };
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
+                BUG();
+
+        if (op.status != GNTST_okay)
+                xenbus_dev_error(dev, op.status,
+                                 "unmapping page at handle %d error %d",
+                                 handle, op.status);
+
+        return op.status;
+}
+EXPORT_SYMBOL_GPL(xenbus_unmap_ring);
+
+
+/**
+ * xenbus_read_driver_state
+ * @path: path for driver
+ *
+ * Return the state of the driver rooted at the given store path, or
+ * XenbusStateUnknown if no state can be read.
+ */
+enum xenbus_state xenbus_read_driver_state(const char *path)
+{
+        enum xenbus_state result;
+        int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
+        if (err)
+                result = XenbusStateUnknown;
+
+        return result;
+}
+EXPORT_SYMBOL_GPL(xenbus_read_driver_state);