Commit 82a29e30 authored by Paul Durrant's avatar Paul Durrant Committed by Anthony PERARD
Browse files

xen: add xenstore watcher infrastructure 



A Xen PV frontend communicates its state to the PV backend by writing to
the 'state' key in the frontend area in xenstore. It is therefore
necessary for a XenDevice implementation to be notified whenever the
value of this key changes.

This patch adds code to do this as follows:

- an 'fd handler' is registered on the libxenstore handle which will be
  triggered whenever a 'watch' event occurs
- primitives are added to xen-bus-helper to add or remove watch events
- a list of Notifier objects is added to XenBus to provide a mechanism
  to call the appropriate 'watch handler' when its associated event
  occurs

The xen-block implementation is extended with a 'frontend_changed' method,
which calls as-yet stub 'connect' and 'disconnect' functions when the
relevant frontend state transitions occur. A subsequent patch will supply
a full implementation for these functions.

Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Reviewed-by: default avatarAnthony Perard <anthony.perard@citrix.com>
Signed-off-by: default avatarAnthony PERARD <anthony.perard@citrix.com>
parent 094a2239

hw/block/trace-events

+2 −0
Original line number Diff line number Diff line
@@ -130,6 +130,8 @@ xen_disk_free(char *name) "%s" 


# hw/block/xen-block.c

xen_block_realize(const char *type, uint32_t disk, uint32_t partition) "%s d%up%u"

xen_block_connect(const char *type, uint32_t disk, uint32_t partition) "%s d%up%u"

xen_block_disconnect(const char *type, uint32_t disk, uint32_t partition) "%s d%up%u"

xen_block_unrealize(const char *type, uint32_t disk, uint32_t partition) "%s d%up%u"

xen_disk_realize(void) ""

xen_disk_unrealize(void) ""

hw/block/xen-block.c

+70 −0
Original line number Diff line number Diff line
@@ -21,6 +21,24 @@ static char *xen_block_get_name(XenDevice *xendev, Error **errp) 
    return g_strdup_printf("%lu", vdev->number);

}



static void xen_block_disconnect(XenDevice *xendev, Error **errp)

{

    XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);

    const char *type = object_get_typename(OBJECT(blockdev));

    XenBlockVdev *vdev = &blockdev->props.vdev;



    trace_xen_block_disconnect(type, vdev->disk, vdev->partition);

}



static void xen_block_connect(XenDevice *xendev, Error **errp)

{

    XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);

    const char *type = object_get_typename(OBJECT(blockdev));

    XenBlockVdev *vdev = &blockdev->props.vdev;



    trace_xen_block_connect(type, vdev->disk, vdev->partition);

}



static void xen_block_unrealize(XenDevice *xendev, Error **errp)

{

    XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
@@ -35,6 +53,9 @@ static void xen_block_unrealize(XenDevice *xendev, Error **errp) 


    trace_xen_block_unrealize(type, vdev->disk, vdev->partition);



    /* Disconnect from the frontend in case this has not already happened */

    xen_block_disconnect(xendev, NULL);



    if (blockdev_class->unrealize) {

        blockdev_class->unrealize(blockdev, errp);

    }
@@ -64,6 +85,54 @@ static void xen_block_realize(XenDevice *xendev, Error **errp) 
    }

}



static void xen_block_frontend_changed(XenDevice *xendev,

                                       enum xenbus_state frontend_state,

                                       Error **errp)

{

    enum xenbus_state backend_state = xen_device_backend_get_state(xendev);

    Error *local_err = NULL;



    switch (frontend_state) {

    case XenbusStateInitialised:

    case XenbusStateConnected:

        if (backend_state == XenbusStateConnected) {

            break;

        }



        xen_block_disconnect(xendev, &local_err);

        if (local_err) {

            error_propagate(errp, local_err);

            break;

        }



        xen_block_connect(xendev, &local_err);

        if (local_err) {

            error_propagate(errp, local_err);

            break;

        }



        xen_device_backend_set_state(xendev, XenbusStateConnected);

        break;



    case XenbusStateClosing:

        xen_device_backend_set_state(xendev, XenbusStateClosing);

        break;



    case XenbusStateClosed:

        xen_block_disconnect(xendev, &local_err);

        if (local_err) {

            error_propagate(errp, local_err);

            break;

        }



        xen_device_backend_set_state(xendev, XenbusStateClosed);

        break;



    default:

        break;

    }

}



static char *disk_to_vbd_name(unsigned int disk)

{

    char *name, *prefix = (disk >= 26) ?
@@ -272,6 +341,7 @@ static void xen_block_class_init(ObjectClass *class, void *data) 


    xendev_class->get_name = xen_block_get_name;

    xendev_class->realize = xen_block_realize;

    xendev_class->frontend_changed = xen_block_frontend_changed;

    xendev_class->unrealize = xen_block_unrealize;



    dev_class->props = xen_block_props;

hw/xen/trace-events

+6 −0
Original line number Diff line number Diff line
@@ -16,13 +16,19 @@ xen_domid_restrict(int err) "err: %u" 
# include/hw/xen/xen-bus.c

xen_bus_realize(void) ""

xen_bus_unrealize(void) ""

xen_bus_add_watch(const char *node, const char *key, char *token) "node: %s key: %s token: %s"

xen_bus_remove_watch(const char *node, const char *key, char *token) "node: %s key: %s token: %s"

xen_bus_watch(const char *token) "token: %s"

xen_device_realize(const char *type, char *name) "type: %s name: %s"

xen_device_unrealize(const char *type, char *name) "type: %s name: %s"

xen_device_backend_state(const char *type, char *name, const char *state) "type: %s name: %s -> %s"

xen_device_frontend_state(const char *type, char *name, const char *state) "type: %s name: %s -> %s"

xen_device_frontend_changed(const char *type, char *name) "type: %s name: %s"



# include/hw/xen/xen-bus-helper.c

xs_node_create(const char *node) "%s"

xs_node_destroy(const char *node) "%s"

xs_node_vprintf(char *path, char *value) "%s %s"

xs_node_vscanf(char *path, char *value) "%s %s"

xs_node_watch(char *path) "%s"

xs_node_unwatch(char *path) "%s"

hw/xen/xen-bus-helper.c

+34 −0
Original line number Diff line number Diff line
@@ -148,3 +148,37 @@ int xs_node_scanf(struct xs_handle *xsh, xs_transaction_t tid, 


    return rc;

}



void xs_node_watch(struct xs_handle *xsh, const char *node, const char *key,

                   char *token, Error **errp)

{

    char *path;



    path = (strlen(node) != 0) ? g_strdup_printf("%s/%s", node, key) :

        g_strdup(key);



    trace_xs_node_watch(path);



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

        error_setg_errno(errp, errno, "failed to watch node '%s'", path);

    }



    g_free(path);

}



void xs_node_unwatch(struct xs_handle *xsh, const char *node,

                     const char *key, const char *token, Error **errp)

{

    char *path;



    path = (strlen(node) != 0) ? g_strdup_printf("%s/%s", node, key) :

        g_strdup(key);



    trace_xs_node_unwatch(path);



    if (!xs_unwatch(xsh, path, token)) {

        error_setg_errno(errp, errno, "failed to unwatch node '%s'", path);

    }



    g_free(path);

}

hw/xen/xen-bus.c

+209 −2
Original line number Diff line number Diff line
@@ -6,6 +6,8 @@ 
 */



#include "qemu/osdep.h"

#include "qemu/main-loop.h"

#include "qemu/uuid.h"

#include "hw/hw.h"

#include "hw/sysbus.h"

#include "hw/xen/xen.h"
@@ -59,6 +61,87 @@ static char *xen_bus_get_dev_path(DeviceState *dev) 
    return xen_device_get_backend_path(XEN_DEVICE(dev));

}



struct XenWatch {

    char *node, *key;

    char *token;

    XenWatchHandler handler;

    void *opaque;

    Notifier notifier;

};



static void watch_notify(Notifier *n, void *data)

{

    XenWatch *watch = container_of(n, XenWatch, notifier);

    const char *token = data;



    if (!strcmp(watch->token, token)) {

        watch->handler(watch->opaque);

    }

}



static XenWatch *new_watch(const char *node, const char *key,

                           XenWatchHandler handler, void *opaque)

{

    XenWatch *watch = g_new0(XenWatch, 1);

    QemuUUID uuid;



    qemu_uuid_generate(&uuid);



    watch->token = qemu_uuid_unparse_strdup(&uuid);

    watch->node = g_strdup(node);

    watch->key = g_strdup(key);

    watch->handler = handler;

    watch->opaque = opaque;

    watch->notifier.notify = watch_notify;



    return watch;

}



static void free_watch(XenWatch *watch)

{

    g_free(watch->token);

    g_free(watch->key);

    g_free(watch->node);



    g_free(watch);

}



static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node,

                                   const char *key, XenWatchHandler handler,

                                   void *opaque, Error **errp)

{

    XenWatch *watch = new_watch(node, key, handler, opaque);

    Error *local_err = NULL;



    trace_xen_bus_add_watch(watch->node, watch->key, watch->token);



    notifier_list_add(&xenbus->watch_notifiers, &watch->notifier);



    xs_node_watch(xenbus->xsh, node, key, watch->token, &local_err);

    if (local_err) {

        error_propagate(errp, local_err);



        notifier_remove(&watch->notifier);

        free_watch(watch);



        return NULL;

    }



    return watch;

}



static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch,

                                 Error **errp)

{

    trace_xen_bus_remove_watch(watch->node, watch->key, watch->token);



    xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token,

                    errp);



    notifier_remove(&watch->notifier);

    free_watch(watch);

}



static void xen_bus_unrealize(BusState *bus, Error **errp)

{

    XenBus *xenbus = XEN_BUS(bus);
@@ -69,9 +152,33 @@ static void xen_bus_unrealize(BusState *bus, Error **errp) 
        return;

    }



    qemu_set_fd_handler(xs_fileno(xenbus->xsh), NULL, NULL, NULL);



    xs_close(xenbus->xsh);

}



static void xen_bus_watch(void *opaque)

{

    XenBus *xenbus = opaque;

    char **v;

    const char *token;



    g_assert(xenbus->xsh);



    v = xs_check_watch(xenbus->xsh);

    if (!v) {

        return;

    }



    token = v[XS_WATCH_TOKEN];



    trace_xen_bus_watch(token);



    notifier_list_notify(&xenbus->watch_notifiers, (void *)token);



    free(v);

}



static void xen_bus_realize(BusState *bus, Error **errp)

{

    XenBus *xenbus = XEN_BUS(bus);
@@ -92,6 +199,9 @@ static void xen_bus_realize(BusState *bus, Error **errp) 
        xenbus->backend_id = 0; /* Assume lack of node means dom0 */

    }



    notifier_list_init(&xenbus->watch_notifiers);

    qemu_set_fd_handler(xs_fileno(xenbus->xsh), xen_bus_watch, NULL,

                        xenbus);

    return;



fail:
@@ -139,7 +249,24 @@ static void xen_device_backend_printf(XenDevice *xendev, const char *key, 
    }

}



static void xen_device_backend_set_state(XenDevice *xendev,

static int xen_device_backend_scanf(XenDevice *xendev, const char *key,

                                    const char *fmt, ...)

{

    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));

    va_list ap;

    int rc;



    g_assert(xenbus->xsh);



    va_start(ap, fmt);

    rc = xs_node_vscanf(xenbus->xsh, XBT_NULL, xendev->backend_path, key,

                        NULL, fmt, ap);

    va_end(ap);



    return rc;

}



void xen_device_backend_set_state(XenDevice *xendev,

                                  enum xenbus_state state)

{

    const char *type = object_get_typename(OBJECT(xendev));
@@ -155,6 +282,11 @@ static void xen_device_backend_set_state(XenDevice *xendev, 
    xen_device_backend_printf(xendev, "state", "%u", state);

}



enum xenbus_state xen_device_backend_get_state(XenDevice *xendev)

{

    return xendev->backend_state;

}



static void xen_device_backend_create(XenDevice *xendev, Error **errp)

{

    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
@@ -218,6 +350,23 @@ static void xen_device_frontend_printf(XenDevice *xendev, const char *key, 
    }

}



static int xen_device_frontend_scanf(XenDevice *xendev, const char *key,

                                     const char *fmt, ...)

{

    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));

    va_list ap;

    int rc;



    g_assert(xenbus->xsh);



    va_start(ap, fmt);

    rc = xs_node_vscanf(xenbus->xsh, XBT_NULL, xendev->frontend_path, key,

                        NULL, fmt, ap);

    va_end(ap);



    return rc;

}



static void xen_device_frontend_set_state(XenDevice *xendev,

                                          enum xenbus_state state)

{
@@ -234,6 +383,50 @@ static void xen_device_frontend_set_state(XenDevice *xendev, 
    xen_device_frontend_printf(xendev, "state", "%u", state);

}



static void xen_device_frontend_changed(void *opaque)

{

    XenDevice *xendev = opaque;

    XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);

    const char *type = object_get_typename(OBJECT(xendev));

    enum xenbus_state state;



    trace_xen_device_frontend_changed(type, xendev->name);



    if (xen_device_frontend_scanf(xendev, "state", "%u", &state) != 1) {

        state = XenbusStateUnknown;

    }



    xen_device_frontend_set_state(xendev, state);



    if (xendev_class->frontend_changed) {

        Error *local_err = NULL;



        xendev_class->frontend_changed(xendev, state, &local_err);



        if (local_err) {

            error_reportf_err(local_err, "frontend change error: ");

        }

    }



    /*

     * If a backend is still 'online' then its state should be cycled

     * back round to InitWait in order for a new frontend instance to

     * connect. This may happen when, for example, a frontend driver is

     * re-installed or updated.

     */

    if (xendev->backend_state == XenbusStateClosed) {

        unsigned int online;



        if (xen_device_backend_scanf(xendev, "online", "%u", &online) != 1) {

            online = 0;

        }



        if (online) {

            xen_device_backend_set_state(xendev, XenbusStateInitWait);

        }

    }

}



static void xen_device_frontend_create(XenDevice *xendev, Error **errp)

{

    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
@@ -254,6 +447,15 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp) 
    if (local_err) {

        error_propagate_prepend(errp, local_err,

                                "failed to create frontend: ");

        return;

    }



    xendev->frontend_state_watch =

        xen_bus_add_watch(xenbus, xendev->frontend_path, "state",

                          xen_device_frontend_changed, xendev, &local_err);

    if (local_err) {

        error_propagate_prepend(errp, local_err,

                                "failed to watch frontend state: ");

    }

}
@@ -262,6 +464,11 @@ static void xen_device_frontend_destroy(XenDevice *xendev) 
    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));

    Error *local_err = NULL;



    if (xendev->frontend_state_watch) {

        xen_bus_remove_watch(xenbus, xendev->frontend_state_watch, NULL);

        xendev->frontend_state_watch = NULL;

    }



    if (!xendev->frontend_path) {

        return;

    }