Archipelago » qemu

/*

 *  xen backend driver infrastructure

 *  (c) 2008 Gerd Hoffmann <kraxel@redhat.com>

 *

 *  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; under version 2 of the License.

 *

 *  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, see <http://www.gnu.org/licenses/>.

 */

/*

 * TODO: add some xenbus / xenstore concepts overview here.

 */

#include <stdio.h>

#include <stdlib.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include <fcntl.h>

#include <inttypes.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <sys/signal.h>

#include <xs.h>

#include <xenctrl.h>

#include <xen/grant_table.h>

#include "hw.h"

#include "qemu-char.h"

#include "qemu-log.h"

#include "xen_backend.h"

/* ------------------------------------------------------------- */

/* public */

int xen_xc;

struct xs_handle *xenstore = NULL;

const char *xen_protocol;

/* private */

static QTAILQ_HEAD(XenDeviceHead, XenDevice) xendevs = QTAILQ_HEAD_INITIALIZER(xendevs);

static int debug = 0;

/* ------------------------------------------------------------- */

int xenstore_write_str(const char *base, const char *node, const char *val)

{

    char abspath[XEN_BUFSIZE];

    snprintf(abspath, sizeof(abspath), "%s/%s", base, node);

    if (!xs_write(xenstore, 0, abspath, val, strlen(val)))

        return -1;

    return 0;

}

char *xenstore_read_str(const char *base, const char *node)

{

    char abspath[XEN_BUFSIZE];

    unsigned int len;

    char *str, *ret = NULL;

    snprintf(abspath, sizeof(abspath), "%s/%s", base, node);

    str = xs_read(xenstore, 0, abspath, &len);

    if (str != NULL) {

        /* move to qemu-allocated memory to make sure

         * callers can savely qemu_free() stuff. */

        ret = qemu_strdup(str);

        free(str);

    }

    return ret;

}

int xenstore_write_int(const char *base, const char *node, int ival)

{

    char val[32];

    snprintf(val, sizeof(val), "%d", ival);

    return xenstore_write_str(base, node, val);

}

int xenstore_read_int(const char *base, const char *node, int *ival)

{

    char *val;

    int rc = -1;

    val = xenstore_read_str(base, node);

    if (val && 1 == sscanf(val, "%d", ival))

        rc = 0;

    qemu_free(val);

    return rc;

}

int xenstore_write_be_str(struct XenDevice *xendev, const char *node, const char *val)

{

    return xenstore_write_str(xendev->be, node, val);

}

int xenstore_write_be_int(struct XenDevice *xendev, const char *node, int ival)

{

    return xenstore_write_int(xendev->be, node, ival);

}

char *xenstore_read_be_str(struct XenDevice *xendev, const char *node)

{

    return xenstore_read_str(xendev->be, node);

}

int xenstore_read_be_int(struct XenDevice *xendev, const char *node, int *ival)

{

    return xenstore_read_int(xendev->be, node, ival);

}

char *xenstore_read_fe_str(struct XenDevice *xendev, const char *node)

{

    return xenstore_read_str(xendev->fe, node);

}

int xenstore_read_fe_int(struct XenDevice *xendev, const char *node, int *ival)

{

    return xenstore_read_int(xendev->fe, node, ival);

}

/* ------------------------------------------------------------- */

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";

}

int xen_be_set_state(struct XenDevice *xendev, enum xenbus_state state)

{

    int rc;

    rc = xenstore_write_be_int(xendev, "state", state);

    if (rc < 0)

        return rc;

    xen_be_printf(xendev, 1, "backend state: %s -> %s\n",

                  xenbus_strstate(xendev->be_state), xenbus_strstate(state));

    xendev->be_state = state;

    return 0;

}

/* ------------------------------------------------------------- */

struct XenDevice *xen_be_find_xendev(const char *type, int dom, int dev)

{

    struct XenDevice *xendev;

    QTAILQ_FOREACH(xendev, &xendevs, next) {

        if (xendev->dom != dom)

            continue;

        if (xendev->dev != dev)

            continue;

        if (strcmp(xendev->type, type) != 0)

            continue;

        return xendev;

    }

    return NULL;

}

/*

 * get xen backend device, allocate a new one if it doesn't exist.

 */

static struct XenDevice *xen_be_get_xendev(const char *type, int dom, int dev,

                                           struct XenDevOps *ops)

{

    struct XenDevice *xendev;

    char *dom0;

    xendev = xen_be_find_xendev(type, dom, dev);

    if (xendev)

        return xendev;

    /* init new xendev */

    xendev = qemu_mallocz(ops->size);

    xendev->type  = type;

    xendev->dom   = dom;

    xendev->dev   = dev;

    xendev->ops   = ops;

    dom0 = xs_get_domain_path(xenstore, 0);

    snprintf(xendev->be, sizeof(xendev->be), "%s/backend/%s/%d/%d",

             dom0, xendev->type, xendev->dom, xendev->dev);

    snprintf(xendev->name, sizeof(xendev->name), "%s-%d",

             xendev->type, xendev->dev);

    free(dom0);

    xendev->debug      = debug;

    xendev->local_port = -1;

    xendev->evtchndev = xc_evtchn_open();

    if (xendev->evtchndev < 0) {

        xen_be_printf(NULL, 0, "can't open evtchn device\n");

        qemu_free(xendev);

        return NULL;

    }

    fcntl(xc_evtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);

    if (ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {

        xendev->gnttabdev = xc_gnttab_open();

        if (xendev->gnttabdev < 0) {

            xen_be_printf(NULL, 0, "can't open gnttab device\n");

            xc_evtchn_close(xendev->evtchndev);

            qemu_free(xendev);

            return NULL;

        }

    } else {

        xendev->gnttabdev = -1;

    }

    QTAILQ_INSERT_TAIL(&xendevs, xendev, next);

    if (xendev->ops->alloc)

        xendev->ops->alloc(xendev);

    return xendev;

}

/*

 * release xen backend device.

 */

static struct XenDevice *xen_be_del_xendev(int dom, int dev)

{

    struct XenDevice *xendev, *xnext;

    /*

     * This is pretty much like QTAILQ_FOREACH(xendev, &xendevs, next) but

     * we save the next pointer in xnext because we might free xendev.

     */

    xnext = xendevs.tqh_first;

    while (xnext) {

        xendev = xnext;

        xnext = xendev->next.tqe_next;

        if (xendev->dom != dom)

            continue;

        if (xendev->dev != dev && dev != -1)

            continue;

        if (xendev->ops->free)

            xendev->ops->free(xendev);

        if (xendev->fe) {

            char token[XEN_BUFSIZE];

            snprintf(token, sizeof(token), "fe:%p", xendev);

            xs_unwatch(xenstore, xendev->fe, token);

            qemu_free(xendev->fe);

        }

        if (xendev->evtchndev >= 0)

            xc_evtchn_close(xendev->evtchndev);

        if (xendev->gnttabdev >= 0)

            xc_gnttab_close(xendev->gnttabdev);

        QTAILQ_REMOVE(&xendevs, xendev, next);

        qemu_free(xendev);

    }

    return NULL;

}

/*

 * Sync internal data structures on xenstore updates.

 * Node specifies the changed field.  node = NULL means

 * update all fields (used for initialization).

 */

static void xen_be_backend_changed(struct XenDevice *xendev, const char *node)

{

    if (node == NULL  ||  strcmp(node, "online") == 0) {

        if (xenstore_read_be_int(xendev, "online", &xendev->online) == -1)

            xendev->online = 0;

    }

    if (node) {

        xen_be_printf(xendev, 2, "backend update: %s\n", node);

        if (xendev->ops->backend_changed)

            xendev->ops->backend_changed(xendev, node);

    }

}

static void xen_be_frontend_changed(struct XenDevice *xendev, const char *node)

{

    int fe_state;

    if (node == NULL  ||  strcmp(node, "state") == 0) {

        if (xenstore_read_fe_int(xendev, "state", &fe_state) == -1)

            fe_state = XenbusStateUnknown;

        if (xendev->fe_state != fe_state)

            xen_be_printf(xendev, 1, "frontend state: %s -> %s\n",

                          xenbus_strstate(xendev->fe_state),

                          xenbus_strstate(fe_state));

        xendev->fe_state = fe_state;

    }

    if (node == NULL  ||  strcmp(node, "protocol") == 0) {

        qemu_free(xendev->protocol);

        xendev->protocol = xenstore_read_fe_str(xendev, "protocol");

        if (xendev->protocol)

            xen_be_printf(xendev, 1, "frontend protocol: %s\n", xendev->protocol);

    }

    if (node) {

        xen_be_printf(xendev, 2, "frontend update: %s\n", node);

        if (xendev->ops->frontend_changed)

            xendev->ops->frontend_changed(xendev, node);

    }

}

/* ------------------------------------------------------------- */

/* Check for possible state transitions and perform them.        */

/*

 * Initial xendev setup.  Read frontend path, register watch for it.

 * Should succeed once xend finished setting up the backend device.

 *

 * Also sets initial state (-> Initializing) when done.  Which

 * only affects the xendev->be_state variable as xenbus should

 * already be put into that state by xend.

 */

static int xen_be_try_setup(struct XenDevice *xendev)

{

    char token[XEN_BUFSIZE];

    int be_state;

    if (xenstore_read_be_int(xendev, "state", &be_state) == -1) {

        xen_be_printf(xendev, 0, "reading backend state failed\n");

        return -1;

    }

    if (be_state != XenbusStateInitialising) {

        xen_be_printf(xendev, 0, "initial backend state is wrong (%s)\n",

                      xenbus_strstate(be_state));

        return -1;

    }

    xendev->fe = xenstore_read_be_str(xendev, "frontend");

    if (xendev->fe == NULL) {

        xen_be_printf(xendev, 0, "reading frontend path failed\n");

        return -1;

    }

    /* setup frontend watch */

    snprintf(token, sizeof(token), "fe:%p", xendev);

    if (!xs_watch(xenstore, xendev->fe, token)) {

        xen_be_printf(xendev, 0, "watching frontend path (%s) failed\n",

                      xendev->fe);

        return -1;

    }

    xen_be_set_state(xendev, XenbusStateInitialising);

    xen_be_backend_changed(xendev, NULL);

    xen_be_frontend_changed(xendev, NULL);

    return 0;

}

/*

 * Try initialize xendev.  Prepare everything the backend can do

 * without synchronizing with the frontend.  Fakes hotplug-status.  No

 * hotplug involved here because this is about userspace drivers, thus

 * there are kernel backend devices which could invoke hotplug.

 *

 * Goes to InitWait on success.

 */

static int xen_be_try_init(struct XenDevice *xendev)

{

    int rc = 0;

    if (!xendev->online) {

        xen_be_printf(xendev, 1, "not online\n");

        return -1;

    }

    if (xendev->ops->init)

        rc = xendev->ops->init(xendev);

    if (rc != 0) {

        xen_be_printf(xendev, 1, "init() failed\n");

        return rc;

    }

    xenstore_write_be_str(xendev, "hotplug-status", "connected");

    xen_be_set_state(xendev, XenbusStateInitWait);

    return 0;

}

/*

 * Try to connect xendev.  Depends on the frontend being ready

 * for it (shared ring and evtchn info in xenstore, state being

 * Initialised or Connected).

 *

 * Goes to Connected on success.

 */

static int xen_be_try_connect(struct XenDevice *xendev)

{

    int rc = 0;

    if (xendev->fe_state != XenbusStateInitialised  &&

        xendev->fe_state != XenbusStateConnected) {

        if (xendev->ops->flags & DEVOPS_FLAG_IGNORE_STATE) {

            xen_be_printf(xendev, 2, "frontend not ready, ignoring\n");

        } else {

            xen_be_printf(xendev, 2, "frontend not ready (yet)\n");

            return -1;

        }

    }

    if (xendev->ops->connect)

        rc = xendev->ops->connect(xendev);

    if (rc != 0) {

        xen_be_printf(xendev, 0, "connect() failed\n");

        return rc;

    }

    xen_be_set_state(xendev, XenbusStateConnected);

    return 0;

}

/*

 * Teardown connection.

 *

 * Goes to Closed when done.

 */

static void xen_be_disconnect(struct XenDevice *xendev, enum xenbus_state state)

{

    if (xendev->be_state != XenbusStateClosing &&

        xendev->be_state != XenbusStateClosed  &&

        xendev->ops->disconnect)

        xendev->ops->disconnect(xendev);

    if (xendev->be_state != state)

        xen_be_set_state(xendev, state);

}

/*

 * Try to reset xendev, for reconnection by another frontend instance.

 */

static int xen_be_try_reset(struct XenDevice *xendev)

{

    if (xendev->fe_state != XenbusStateInitialising)

        return -1;

    xen_be_printf(xendev, 1, "device reset (for re-connect)\n");

    xen_be_set_state(xendev, XenbusStateInitialising);

    return 0;

}

/*

 * state change dispatcher function

 */

void xen_be_check_state(struct XenDevice *xendev)

{

    int rc = 0;

    /* frontend may request shutdown from almost anywhere */

    if (xendev->fe_state == XenbusStateClosing ||

        xendev->fe_state == XenbusStateClosed) {

        xen_be_disconnect(xendev, xendev->fe_state);

        return;

    }

    /* check for possible backend state transitions */

    for (;;) {

        switch (xendev->be_state) {

        case XenbusStateUnknown:

            rc = xen_be_try_setup(xendev);

            break;

        case XenbusStateInitialising:

            rc = xen_be_try_init(xendev);

            break;

        case XenbusStateInitWait:

            rc = xen_be_try_connect(xendev);

            break;

        case XenbusStateClosed:

            rc = xen_be_try_reset(xendev);

            break;

        default:

            rc = -1;

        }

        if (rc != 0)

            break;

    }

}

/* ------------------------------------------------------------- */

static int xenstore_scan(const char *type, int dom, struct XenDevOps *ops)

{

    struct XenDevice *xendev;

    char path[XEN_BUFSIZE], token[XEN_BUFSIZE];

    char **dev = NULL, *dom0;

    unsigned int cdev, j;

    /* setup watch */

    dom0 = xs_get_domain_path(xenstore, 0);

    snprintf(token, sizeof(token), "be:%p:%d:%p", type, dom, ops);

    snprintf(path, sizeof(path), "%s/backend/%s/%d", dom0, type, dom);

    free(dom0);

    if (!xs_watch(xenstore, path, token)) {

        xen_be_printf(NULL, 0, "xen be: watching backend path (%s) failed\n", path);

        return -1;

    }

    /* look for backends */

    dev = xs_directory(xenstore, 0, path, &cdev);

    if (!dev)

        return 0;

    for (j = 0; j < cdev; j++) {

        xendev = xen_be_get_xendev(type, dom, atoi(dev[j]), ops);

        if (xendev == NULL)

            continue;

        xen_be_check_state(xendev);

    }

    free(dev);

    return 0;

}

static void xenstore_update_be(char *watch, char *type, int dom,

                               struct XenDevOps *ops)

{

    struct XenDevice *xendev;

    char path[XEN_BUFSIZE], *dom0;

    unsigned int len, dev;

    dom0 = xs_get_domain_path(xenstore, 0);

    len = snprintf(path, sizeof(path), "%s/backend/%s/%d", dom0, type, dom);

    free(dom0);

    if (strncmp(path, watch, len) != 0)

        return;

    if (sscanf(watch+len, "/%u/%255s", &dev, path) != 2) {

        strcpy(path, "");

        if (sscanf(watch+len, "/%u", &dev) != 1)

            dev = -1;

    }

    if (dev == -1)

        return;

    if (0) {

        /* FIXME: detect devices being deleted from xenstore ... */

        xen_be_del_xendev(dom, dev);

    }

    xendev = xen_be_get_xendev(type, dom, dev, ops);

    if (xendev != NULL) {

        xen_be_backend_changed(xendev, path);

        xen_be_check_state(xendev);

    }

}

static void xenstore_update_fe(char *watch, struct XenDevice *xendev)

{

    char *node;

    unsigned int len;

    len = strlen(xendev->fe);

    if (strncmp(xendev->fe, watch, len) != 0)

        return;

    if (watch[len] != '/')

        return;

    node = watch + len + 1;

    xen_be_frontend_changed(xendev, node);

    xen_be_check_state(xendev);

}

static void xenstore_update(void *unused)

{

    char **vec = NULL;

    intptr_t type, ops, ptr;

    unsigned int dom, count;

    vec = xs_read_watch(xenstore, &count);

    if (vec == NULL)

        goto cleanup;

    if (sscanf(vec[XS_WATCH_TOKEN], "be:%" PRIxPTR ":%d:%" PRIxPTR,

               &type, &dom, &ops) == 3)

        xenstore_update_be(vec[XS_WATCH_PATH], (void*)type, dom, (void*)ops);

    if (sscanf(vec[XS_WATCH_TOKEN], "fe:%" PRIxPTR, &ptr) == 1)

        xenstore_update_fe(vec[XS_WATCH_PATH], (void*)ptr);

cleanup:

    qemu_free(vec);

}

static void xen_be_evtchn_event(void *opaque)

{

    struct XenDevice *xendev = opaque;

    evtchn_port_t port;

    port = xc_evtchn_pending(xendev->evtchndev);

    if (port != xendev->local_port) {

        xen_be_printf(xendev, 0, "xc_evtchn_pending returned %d (expected %d)\n",

                      port, xendev->local_port);

        return;

    }

    xc_evtchn_unmask(xendev->evtchndev, port);

    if (xendev->ops->event)

        xendev->ops->event(xendev);

}

/* -------------------------------------------------------------------- */

int xen_be_init(void)

{

    xenstore = xs_daemon_open();

    if (!xenstore) {

        xen_be_printf(NULL, 0, "can't connect to xenstored\n");

        return -1;

    }

    if (qemu_set_fd_handler(xs_fileno(xenstore), xenstore_update, NULL, NULL) < 0)

        goto err;

    xen_xc = xc_interface_open();

    if (xen_xc == -1) {

        xen_be_printf(NULL, 0, "can't open xen interface\n");

        goto err;

    }

    return 0;

err:

    qemu_set_fd_handler(xs_fileno(xenstore), NULL, NULL, NULL);

    xs_daemon_close(xenstore);

    xenstore = NULL;

    return -1;

}

int xen_be_register(const char *type, struct XenDevOps *ops)

{

    return xenstore_scan(type, xen_domid, ops);

}

int xen_be_bind_evtchn(struct XenDevice *xendev)

{

    if (xendev->local_port != -1)

        return 0;

    xendev->local_port = xc_evtchn_bind_interdomain

        (xendev->evtchndev, xendev->dom, xendev->remote_port);

    if (xendev->local_port == -1) {

        xen_be_printf(xendev, 0, "xc_evtchn_bind_interdomain failed\n");

        return -1;

    }

    xen_be_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);

    qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev),

                        xen_be_evtchn_event, NULL, xendev);

    return 0;

}

void xen_be_unbind_evtchn(struct XenDevice *xendev)

{

    if (xendev->local_port == -1)

        return;

    qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev), NULL, NULL, NULL);

    xc_evtchn_unbind(xendev->evtchndev, xendev->local_port);

    xen_be_printf(xendev, 2, "unbind evtchn port %d\n", xendev->local_port);

    xendev->local_port = -1;

}

int xen_be_send_notify(struct XenDevice *xendev)

{

    return xc_evtchn_notify(xendev->evtchndev, xendev->local_port);

}

/*

 * msg_level:

 *  0 == errors (stderr + logfile).

 *  1 == informative debug messages (logfile only).

 *  2 == noisy debug messages (logfile only).

 *  3 == will flood your log (logfile only).

 */

void xen_be_printf(struct XenDevice *xendev, int msg_level, const char *fmt, ...)

{

    va_list args;

    if (xendev) {

        if (msg_level > xendev->debug)

            return;

        qemu_log("xen be: %s: ", xendev->name);

        if (msg_level == 0)

            fprintf(stderr, "xen be: %s: ", xendev->name);

    } else {

        if (msg_level > debug)

            return;

        qemu_log("xen be core: ");

        if (msg_level == 0)

            fprintf(stderr, "xen be core: ");

    }

    va_start(args, fmt);

    qemu_log_vprintf(fmt, args);

    va_end(args);

    if (msg_level == 0) {

        va_start(args, fmt);

        vfprintf(stderr, fmt, args);

        va_end(args);

    }

    qemu_log_flush();

}