xenbus.c

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/*
 * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ipxe/malloc.h>
#include <ipxe/device.h>
#include <ipxe/timer.h>
#include <ipxe/nap.h>
#include <ipxe/xen.h>
#include <ipxe/xenstore.h>
#include <ipxe/xenbus.h>

/** @file
 *
 * Xen device bus
 *
 */

/* Disambiguate the various error causes */
#define ETIMEDOUT_UNKNOWN                                               \
        __einfo_error ( EINFO_ETIMEDOUT_UNKNOWN )
#define EINFO_ETIMEDOUT_UNKNOWN                                         \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateUnknown,          \
                          "Unknown" )
#define ETIMEDOUT_INITIALISING                                          \
        __einfo_error ( EINFO_ETIMEDOUT_INITIALISING )
#define EINFO_ETIMEDOUT_INITIALISING                                    \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateInitialising,     \
                          "Initialising" )
#define ETIMEDOUT_INITWAIT                                              \
        __einfo_error ( EINFO_ETIMEDOUT_INITWAIT )
#define EINFO_ETIMEDOUT_INITWAIT                                        \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateInitWait,         \
                          "InitWait" )
#define ETIMEDOUT_INITIALISED                                           \
        __einfo_error ( EINFO_ETIMEDOUT_INITIALISED )
#define EINFO_ETIMEDOUT_INITIALISED                                     \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateInitialised,      \
                          "Initialised" )
#define ETIMEDOUT_CONNECTED                                             \
        __einfo_error ( EINFO_ETIMEDOUT_CONNECTED )
#define EINFO_ETIMEDOUT_CONNECTED                                       \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateConnected,        \
                          "Connected" )
#define ETIMEDOUT_CLOSING                                               \
        __einfo_error ( EINFO_ETIMEDOUT_CLOSING )
#define EINFO_ETIMEDOUT_CLOSING                                         \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateClosing,          \
                          "Closing" )
#define ETIMEDOUT_CLOSED                                                \
        __einfo_error ( EINFO_ETIMEDOUT_CLOSED )
#define EINFO_ETIMEDOUT_CLOSED                                          \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateClosed,           \
                          "Closed" )
#define ETIMEDOUT_RECONFIGURING                                         \
        __einfo_error ( EINFO_ETIMEDOUT_RECONFIGURING )
#define EINFO_ETIMEDOUT_RECONFIGURING                                   \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateReconfiguring,    \
                          "Reconfiguring" )
#define ETIMEDOUT_RECONFIGURED                                          \
        __einfo_error ( EINFO_ETIMEDOUT_RECONFIGURED )
#define EINFO_ETIMEDOUT_RECONFIGURED                                    \
        __einfo_uniqify ( EINFO_ETIMEDOUT, XenbusStateReconfigured,     \
                          "Reconfigured" )
#define ETIMEDOUT_STATE( state )                                        \
        EUNIQ ( EINFO_ETIMEDOUT, (state), ETIMEDOUT_UNKNOWN,            \
                ETIMEDOUT_INITIALISING, ETIMEDOUT_INITWAIT,             \
                ETIMEDOUT_INITIALISED, ETIMEDOUT_CONNECTED,             \
                ETIMEDOUT_CLOSING, ETIMEDOUT_CLOSED,                    \
                ETIMEDOUT_RECONFIGURING, ETIMEDOUT_RECONFIGURED )

/** Maximum time to wait for backend to reach a given state, in ticks */
#define XENBUS_BACKEND_TIMEOUT ( 5 * TICKS_PER_SEC )

/**
 * Set device state
 *
 * @v xendev            Xen device
 * @v state             New state
 * @ret rc              Return status code
 */
int xenbus_set_state ( struct xen_device *xendev, int state ) {
        int rc;

        /* Attempt to set state */
        if ( ( rc = xenstore_write_num ( xendev->xen, state, xendev->key,
                                         "state", NULL ) ) != 0 ) {
                DBGC ( xendev, "XENBUS %s could not set state=\"%d\": %s\n",
                       xendev->key, state, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Get backend state
 *
 * @v xendev            Xen device
 * @ret state           Backend state, or negative error
 */
int xenbus_backend_state ( struct xen_device *xendev ) {
        unsigned long state;
        int rc;

        /* Attempt to get backend state */
        if ( ( rc = xenstore_read_num ( xendev->xen, &state, xendev->backend,
                                        "state", NULL ) ) != 0 ) {
                DBGC ( xendev, "XENBUS %s could not read %s/state: %s\n",
                       xendev->key, xendev->backend, strerror ( rc ) );
                return rc;
        }

        return state;
}

/**
 * Wait for backend to reach a given state
 *
 * @v xendev            Xen device
 * @v state             Desired backend state
 * @ret rc              Return status code
 */
int xenbus_backend_wait ( struct xen_device *xendev, int state ) {
        unsigned long started = currticks();
        unsigned long elapsed;
        unsigned int attempts = 0;
        int current_state;
        int rc;

        /* Wait for backend to reach this state */
        do {

                /* Get current backend state */
                current_state = xenbus_backend_state ( xendev );
                if ( current_state < 0 ) {
                        rc = current_state;
                        return rc;
                }
                if ( current_state == state )
                        return 0;

                /* Allow time for backend to react */
                cpu_nap();

                /* XenStore is a very slow interface; any fixed delay
                 * time would be dwarfed by the XenStore access time.
                 * We therefore use wall clock to time out this
                 * operation.
                 */
                elapsed = ( currticks() - started );
                attempts++;

        } while ( elapsed < XENBUS_BACKEND_TIMEOUT );

        /* Construct status code from current backend state */
        rc = -ETIMEDOUT_STATE ( current_state );
        DBGC ( xendev, "XENBUS %s timed out after %d attempts waiting for "
               "%s/state=\"%d\": %s\n", xendev->key, attempts, xendev->backend,
               state, strerror ( rc ) );

        return rc;
}

/**
 * Find driver for Xen device
 *
 * @v type              Device type
 * @ret driver          Driver, or NULL
 */
static struct xen_driver * xenbus_find_driver ( const char *type ) {
        struct xen_driver *xendrv;

        for_each_table_entry ( xendrv, XEN_DRIVERS ) {
                if ( strcmp ( xendrv->type, type ) == 0 )
                        return xendrv;
        }
        return NULL;
}

/**
 * Probe Xen device
 *
 * @v xen               Xen hypervisor
 * @v parent            Parent device
 * @v instance          Device instance
 * @v driver            Device driver
 * @ret rc              Return status code
 */
static int xenbus_probe_device ( struct xen_hypervisor *xen,
                                 struct device *parent, const char *instance,
                                 struct xen_driver *driver ) {
        const char *type = driver->type;
        struct xen_device *xendev;
        size_t key_len;
        int rc;

        /* Allocate and initialise structure */
        key_len = ( 7 /* "device/" */ + strlen ( type ) + 1 /* "/" */ +
                    strlen ( instance ) + 1 /* NUL */ );
        xendev = zalloc ( sizeof ( *xendev ) + key_len );
        if ( ! xendev ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        snprintf ( xendev->dev.name, sizeof ( xendev->dev.name ), "%s/%s",
                   type, instance );
        xendev->dev.desc.bus_type = BUS_TYPE_XEN;
        INIT_LIST_HEAD ( &xendev->dev.children );
        list_add_tail ( &xendev->dev.siblings, &parent->children );
        xendev->dev.parent = parent;
        xendev->xen = xen;
        xendev->key = ( ( void * ) ( xendev + 1 ) );
        snprintf ( xendev->key, key_len, "device/%s/%s", type, instance );
        xendev->driver = driver;
        xendev->dev.driver_name = driver->name;
        DBGC ( xendev, "XENBUS %s has driver \"%s\"\n", xendev->key,
               xendev->driver->name );

        /* Read backend key */
        if ( ( rc = xenstore_read ( xen, &xendev->backend, xendev->key,
                                    "backend", NULL ) ) != 0 ) {
                DBGC ( xendev, "XENBUS %s could not read backend: %s\n",
                       xendev->key, strerror ( rc ) );
                goto err_read_backend;
        }

        /* Read backend domain ID */
        if ( ( rc = xenstore_read_num ( xen, &xendev->backend_id, xendev->key,
                                        "backend-id", NULL ) ) != 0 ) {
                DBGC ( xendev, "XENBUS %s could not read backend-id: %s\n",
                       xendev->key, strerror ( rc ) );
                goto err_read_backend_id;
        }
        DBGC ( xendev, "XENBUS %s backend=\"%s\" in domain %ld\n",
               xendev->key, xendev->backend, xendev->backend_id );

        /* Probe driver */
        if ( ( rc = xendev->driver->probe ( xendev ) ) != 0 ) {
                DBGC ( xendev, "XENBUS could not probe %s: %s\n",
                       xendev->key, strerror ( rc ) );
                goto err_probe;
        }

        return 0;

        xendev->driver->remove ( xendev );
 err_probe:
 err_read_backend_id:
        free ( xendev->backend );
 err_read_backend:
        list_del ( &xendev->dev.siblings );
        free ( xendev );
 err_alloc:
        return rc;
}

/**
 * Remove Xen device
 *
 * @v xendev            Xen device
 */
static void xenbus_remove_device ( struct xen_device *xendev ) {

        /* Remove device */
        xendev->driver->remove ( xendev );
        free ( xendev->backend );
        list_del ( &xendev->dev.siblings );
        free ( xendev );
}

/**
 * Probe Xen devices of a given type
 *
 * @v xen               Xen hypervisor
 * @v parent            Parent device
 * @v type              Device type
 * @ret rc              Return status code
 */
static int xenbus_probe_type ( struct xen_hypervisor *xen,
                               struct device *parent, const char *type ) {
        struct xen_driver *driver;
        char *children;
        char *child;
        size_t len;
        int rc;

        /* Look for a driver */
        driver = xenbus_find_driver ( type );
        if ( ! driver ) {
                DBGC ( xen, "XENBUS has no driver for \"%s\" devices\n", type );
                /* Not a fatal error */
                rc = 0;
                goto err_no_driver;
        }

        /* Get children of this key */
        if ( ( rc = xenstore_directory ( xen, &children, &len, "device",
                                         type, NULL ) ) != 0 ) {
                DBGC ( xen, "XENBUS could not list \"%s\" devices: %s\n",
                       type, strerror ( rc ) );
                goto err_directory;
        }

        /* Probe each child */
        for ( child = children ; child < ( children + len ) ;
              child += ( strlen ( child ) + 1 /* NUL */ ) ) {
                if ( ( rc = xenbus_probe_device ( xen, parent, child,
                                                  driver ) ) != 0 )
                        goto err_probe_device;
        }

        free ( children );
        return 0;

 err_probe_device:
        free ( children );
 err_directory:
 err_no_driver:
        return rc;
}

/**
 * Probe Xen bus
 *
 * @v xen               Xen hypervisor
 * @v parent            Parent device
 * @ret rc              Return status code
 */
int xenbus_probe ( struct xen_hypervisor *xen, struct device *parent ) {
        char *types;
        char *type;
        size_t len;
        int rc;

        /* Get children of "device" key */
        if ( ( rc = xenstore_directory ( xen, &types, &len, "device",
                                         NULL ) ) != 0 ) {
                DBGC ( xen, "XENBUS could not list device types: %s\n",
                       strerror ( rc ) );
                goto err_directory;
        }

        /* Probe each child type */
        for ( type = types ; type < ( types + len ) ;
              type += ( strlen ( type ) + 1 /* NUL */ ) ) {
                if ( ( rc = xenbus_probe_type ( xen, parent, type ) ) != 0 )
                        goto err_probe_type;
        }

        free ( types );
        return 0;

        xenbus_remove ( xen, parent );
 err_probe_type:
        free ( types );
 err_directory:
        return rc;
}

/**
 * Remove Xen bus
 *
 * @v xen               Xen hypervisor
 * @v parent            Parent device
 */
void xenbus_remove ( struct xen_hypervisor *xen __unused,
                     struct device *parent ) {
        struct xen_device *xendev;
        struct xen_device *tmp;

        /* Remove devices */
        list_for_each_entry_safe ( xendev, tmp, &parent->children,
                                   dev.siblings ) {
                xenbus_remove_device ( xendev );
        }
}