xenbus_client.c

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/******************************************************************************
 * 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/slab.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/page.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>
#include <xen/balloon.h>
#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
#include <xen/xen.h>

#include "xenbus_probe.h"

struct xenbus_map_node {
    struct list_head next;
    union {
        struct vm_struct *area; /* PV */
        struct page *page;     /* HVM */
    };
    grant_handle_t handle;
};

static DEFINE_SPINLOCK(xenbus_valloc_lock);
static LIST_HEAD(xenbus_valloc_pages);

struct xenbus_ring_ops {
    int (*map)(struct xenbus_device *dev, int gnt, void **vaddr);
    int (*unmap)(struct xenbus_device *dev, void *vaddr);
};

static const struct xenbus_ring_ops *ring_ops __read_mostly;

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",
        [XenbusStateReconfiguring] = "Reconfiguring",
        [XenbusStateReconfigured] = "Reconfigured",
    };
    return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
}
EXPORT_SYMBOL_GPL(xenbus_strstate);

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);


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_NOIO | __GFP_HIGH, 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);

static void xenbus_switch_fatal(struct xenbus_device *, int, int,
                const char *, ...);

static int
__xenbus_switch_state(struct xenbus_device *dev,
              enum xenbus_state state, int depth)
{
    /* 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 take a caller's Xenstore transaction
       (something it was trying to in the past) because dev->state
       would not get reset if the transaction was aborted.
     */

    struct xenbus_transaction xbt;
    int current_state;
    int err, abort;

    if (state == dev->state)
        return 0;

again:
    abort = 1;

    err = xenbus_transaction_start(&xbt);
    if (err) {
        xenbus_switch_fatal(dev, depth, err, "starting transaction");
        return 0;
    }

    err = xenbus_scanf(xbt, dev->nodename, "state", "%d", &current_state);
    if (err != 1)
        goto abort;

    err = xenbus_printf(xbt, dev->nodename, "state", "%d", state);
    if (err) {
        xenbus_switch_fatal(dev, depth, err, "writing new state");
        goto abort;
    }

    abort = 0;
abort:
    err = xenbus_transaction_end(xbt, abort);
    if (err) {
        if (err == -EAGAIN && !abort)
            goto again;
        xenbus_switch_fatal(dev, depth, err, "ending transaction");
    } else
        dev->state = state;

    return 0;
}

int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
{
    return __xenbus_switch_state(dev, state, 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);

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);
}


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);

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);

static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
                const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    xenbus_va_dev_error(dev, err, fmt, ap);
    va_end(ap);

    if (!depth)
        __xenbus_switch_state(dev, XenbusStateClosing, 1);
}

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);


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);


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);


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);


int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
{
    return ring_ops->map(dev, gnt_ref, vaddr);
}
EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);

static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
                     int gnt_ref, void **vaddr)
{
    struct gnttab_map_grant_ref op = {
        .flags = GNTMAP_host_map | GNTMAP_contains_pte,
        .ref   = gnt_ref,
        .dom   = dev->otherend_id,
    };
    struct xenbus_map_node *node;
    struct vm_struct *area;
    pte_t *pte;

    *vaddr = NULL;

    node = kzalloc(sizeof(*node), GFP_KERNEL);
    if (!node)
        return -ENOMEM;

    area = alloc_vm_area(PAGE_SIZE, &pte);
    if (!area) {
        kfree(node);
        return -ENOMEM;
    }

    op.host_addr = arbitrary_virt_to_machine(pte).maddr;

    gnttab_batch_map(&op, 1);

    if (op.status != GNTST_okay) {
        free_vm_area(area);
        kfree(node);
        xenbus_dev_fatal(dev, op.status,
                 "mapping in shared page %d from domain %d",
                 gnt_ref, dev->otherend_id);
        return op.status;
    }

    node->handle = op.handle;
    node->area = area;

    spin_lock(&xenbus_valloc_lock);
    list_add(&node->next, &xenbus_valloc_pages);
    spin_unlock(&xenbus_valloc_lock);

    *vaddr = area->addr;
    return 0;
}

static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
                      int gnt_ref, void **vaddr)
{
    struct xenbus_map_node *node;
    int err;
    void *addr;

    *vaddr = NULL;

    node = kzalloc(sizeof(*node), GFP_KERNEL);
    if (!node)
        return -ENOMEM;

    err = alloc_xenballooned_pages(1, &node->page, false /* lowmem */);
    if (err)
        goto out_err;

    addr = pfn_to_kaddr(page_to_pfn(node->page));

    err = xenbus_map_ring(dev, gnt_ref, &node->handle, addr);
    if (err)
        goto out_err;

    spin_lock(&xenbus_valloc_lock);
    list_add(&node->next, &xenbus_valloc_pages);
    spin_unlock(&xenbus_valloc_lock);

    *vaddr = addr;
    return 0;

 out_err:
    free_xenballooned_pages(1, &node->page);
    kfree(node);
    return err;
}


int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
            grant_handle_t *handle, void *vaddr)
{
    struct gnttab_map_grant_ref op;

    gnttab_set_map_op(&op, (unsigned long)vaddr, GNTMAP_host_map, gnt_ref,
              dev->otherend_id);

    gnttab_batch_map(&op, 1);

    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);


int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
{
    return ring_ops->unmap(dev, vaddr);
}
EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);

static int xenbus_unmap_ring_vfree_pv(struct xenbus_device *dev, void *vaddr)
{
    struct xenbus_map_node *node;
    struct gnttab_unmap_grant_ref op = {
        .host_addr = (unsigned long)vaddr,
    };
    unsigned int level;

    spin_lock(&xenbus_valloc_lock);
    list_for_each_entry(node, &xenbus_valloc_pages, next) {
        if (node->area->addr == vaddr) {
            list_del(&node->next);
            goto found;
        }
    }
    node = NULL;
 found:
    spin_unlock(&xenbus_valloc_lock);

    if (!node) {
        xenbus_dev_error(dev, -ENOENT,
                 "can't find mapped virtual address %p", vaddr);
        return GNTST_bad_virt_addr;
    }

    op.handle = node->handle;
    op.host_addr = arbitrary_virt_to_machine(
        lookup_address((unsigned long)vaddr, &level)).maddr;

    if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
        BUG();

    if (op.status == GNTST_okay)
        free_vm_area(node->area);
    else
        xenbus_dev_error(dev, op.status,
                 "unmapping page at handle %d error %d",
                 node->handle, op.status);

    kfree(node);
    return op.status;
}

static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
{
    int rv;
    struct xenbus_map_node *node;
    void *addr;

    spin_lock(&xenbus_valloc_lock);
    list_for_each_entry(node, &xenbus_valloc_pages, next) {
        addr = pfn_to_kaddr(page_to_pfn(node->page));
        if (addr == vaddr) {
            list_del(&node->next);
            goto found;
        }
    }
    node = addr = NULL;
 found:
    spin_unlock(&xenbus_valloc_lock);

    if (!node) {
        xenbus_dev_error(dev, -ENOENT,
                 "can't find mapped virtual address %p", vaddr);
        return GNTST_bad_virt_addr;
    }

    rv = xenbus_unmap_ring(dev, node->handle, addr);

    if (!rv)
        free_xenballooned_pages(1, &node->page);
    else
        WARN(1, "Leaking %p\n", vaddr);

    kfree(node);
    return rv;
}

int xenbus_unmap_ring(struct xenbus_device *dev,
              grant_handle_t handle, void *vaddr)
{
    struct gnttab_unmap_grant_ref op;

    gnttab_set_unmap_op(&op, (unsigned long)vaddr, GNTMAP_host_map, 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);


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);

static const struct xenbus_ring_ops ring_ops_pv = {
    .map = xenbus_map_ring_valloc_pv,
    .unmap = xenbus_unmap_ring_vfree_pv,
};

static const struct xenbus_ring_ops ring_ops_hvm = {
    .map = xenbus_map_ring_valloc_hvm,
    .unmap = xenbus_unmap_ring_vfree_hvm,
};

void __init xenbus_ring_ops_init(void)
{
    if (xen_pv_domain())
        ring_ops = &ring_ops_pv;
    else
        ring_ops = &ring_ops_hvm;
}