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https://github.com/Motorhead1991/qemu.git
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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: Paul Durrant <paul.durrant@citrix.com> Reviewed-by: Anthony Perard <anthony.perard@citrix.com> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Paul Durrant
Anthony PERARD
parent
094a22399f
commit
82a29e3048
7 changed files with 342 additions and 2 deletions
211
hw/xen/xen-bus.c
211
hw/xen/xen-bus.c
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@ -6,6 +6,8 @@
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*/
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#include "qemu/osdep.h"
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#include "qemu/main-loop.h"
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#include "qemu/uuid.h"
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#include "hw/hw.h"
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#include "hw/sysbus.h"
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#include "hw/xen/xen.h"
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@ -59,6 +61,87 @@ static char *xen_bus_get_dev_path(DeviceState *dev)
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return xen_device_get_backend_path(XEN_DEVICE(dev));
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}
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struct XenWatch {
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char *node, *key;
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char *token;
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XenWatchHandler handler;
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void *opaque;
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Notifier notifier;
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};
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static void watch_notify(Notifier *n, void *data)
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{
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XenWatch *watch = container_of(n, XenWatch, notifier);
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const char *token = data;
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if (!strcmp(watch->token, token)) {
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watch->handler(watch->opaque);
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}
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}
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static XenWatch *new_watch(const char *node, const char *key,
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XenWatchHandler handler, void *opaque)
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{
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XenWatch *watch = g_new0(XenWatch, 1);
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QemuUUID uuid;
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qemu_uuid_generate(&uuid);
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watch->token = qemu_uuid_unparse_strdup(&uuid);
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watch->node = g_strdup(node);
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watch->key = g_strdup(key);
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watch->handler = handler;
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watch->opaque = opaque;
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watch->notifier.notify = watch_notify;
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return watch;
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}
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static void free_watch(XenWatch *watch)
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{
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g_free(watch->token);
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g_free(watch->key);
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g_free(watch->node);
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g_free(watch);
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}
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static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node,
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const char *key, XenWatchHandler handler,
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void *opaque, Error **errp)
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{
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XenWatch *watch = new_watch(node, key, handler, opaque);
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Error *local_err = NULL;
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trace_xen_bus_add_watch(watch->node, watch->key, watch->token);
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notifier_list_add(&xenbus->watch_notifiers, &watch->notifier);
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xs_node_watch(xenbus->xsh, node, key, watch->token, &local_err);
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if (local_err) {
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error_propagate(errp, local_err);
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notifier_remove(&watch->notifier);
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free_watch(watch);
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return NULL;
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}
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return watch;
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}
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static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch,
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Error **errp)
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{
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trace_xen_bus_remove_watch(watch->node, watch->key, watch->token);
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xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token,
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errp);
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notifier_remove(&watch->notifier);
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free_watch(watch);
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}
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static void xen_bus_unrealize(BusState *bus, Error **errp)
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{
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XenBus *xenbus = XEN_BUS(bus);
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@ -69,9 +152,33 @@ static void xen_bus_unrealize(BusState *bus, Error **errp)
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return;
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}
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qemu_set_fd_handler(xs_fileno(xenbus->xsh), NULL, NULL, NULL);
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xs_close(xenbus->xsh);
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}
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static void xen_bus_watch(void *opaque)
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{
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XenBus *xenbus = opaque;
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char **v;
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const char *token;
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g_assert(xenbus->xsh);
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v = xs_check_watch(xenbus->xsh);
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if (!v) {
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return;
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}
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token = v[XS_WATCH_TOKEN];
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trace_xen_bus_watch(token);
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notifier_list_notify(&xenbus->watch_notifiers, (void *)token);
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free(v);
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}
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static void xen_bus_realize(BusState *bus, Error **errp)
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{
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XenBus *xenbus = XEN_BUS(bus);
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@ -92,6 +199,9 @@ static void xen_bus_realize(BusState *bus, Error **errp)
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xenbus->backend_id = 0; /* Assume lack of node means dom0 */
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}
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notifier_list_init(&xenbus->watch_notifiers);
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qemu_set_fd_handler(xs_fileno(xenbus->xsh), xen_bus_watch, NULL,
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xenbus);
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return;
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fail:
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@ -139,8 +249,25 @@ static void xen_device_backend_printf(XenDevice *xendev, const char *key,
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}
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}
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static void xen_device_backend_set_state(XenDevice *xendev,
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enum xenbus_state state)
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static int xen_device_backend_scanf(XenDevice *xendev, const char *key,
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const char *fmt, ...)
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{
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XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
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va_list ap;
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int rc;
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g_assert(xenbus->xsh);
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va_start(ap, fmt);
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rc = xs_node_vscanf(xenbus->xsh, XBT_NULL, xendev->backend_path, key,
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NULL, fmt, ap);
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va_end(ap);
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return rc;
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}
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void xen_device_backend_set_state(XenDevice *xendev,
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enum xenbus_state state)
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{
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const char *type = object_get_typename(OBJECT(xendev));
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@ -155,6 +282,11 @@ static void xen_device_backend_set_state(XenDevice *xendev,
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xen_device_backend_printf(xendev, "state", "%u", state);
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}
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enum xenbus_state xen_device_backend_get_state(XenDevice *xendev)
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{
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return xendev->backend_state;
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}
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static void xen_device_backend_create(XenDevice *xendev, Error **errp)
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{
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XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
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@ -218,6 +350,23 @@ static void xen_device_frontend_printf(XenDevice *xendev, const char *key,
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}
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}
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static int xen_device_frontend_scanf(XenDevice *xendev, const char *key,
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const char *fmt, ...)
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{
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XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
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va_list ap;
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int rc;
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g_assert(xenbus->xsh);
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va_start(ap, fmt);
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rc = xs_node_vscanf(xenbus->xsh, XBT_NULL, xendev->frontend_path, key,
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NULL, fmt, ap);
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va_end(ap);
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return rc;
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}
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static void xen_device_frontend_set_state(XenDevice *xendev,
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enum xenbus_state state)
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{
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@ -234,6 +383,50 @@ static void xen_device_frontend_set_state(XenDevice *xendev,
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xen_device_frontend_printf(xendev, "state", "%u", state);
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}
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static void xen_device_frontend_changed(void *opaque)
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{
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XenDevice *xendev = opaque;
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XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
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const char *type = object_get_typename(OBJECT(xendev));
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enum xenbus_state state;
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trace_xen_device_frontend_changed(type, xendev->name);
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if (xen_device_frontend_scanf(xendev, "state", "%u", &state) != 1) {
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state = XenbusStateUnknown;
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}
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xen_device_frontend_set_state(xendev, state);
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if (xendev_class->frontend_changed) {
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Error *local_err = NULL;
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xendev_class->frontend_changed(xendev, state, &local_err);
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if (local_err) {
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error_reportf_err(local_err, "frontend change error: ");
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}
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}
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/*
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* If a backend is still 'online' then its state should be cycled
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* back round to InitWait in order for a new frontend instance to
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* connect. This may happen when, for example, a frontend driver is
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* re-installed or updated.
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*/
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if (xendev->backend_state == XenbusStateClosed) {
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unsigned int online;
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if (xen_device_backend_scanf(xendev, "online", "%u", &online) != 1) {
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online = 0;
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}
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if (online) {
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xen_device_backend_set_state(xendev, XenbusStateInitWait);
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}
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}
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}
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static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
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{
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XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
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@ -254,6 +447,15 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
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if (local_err) {
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error_propagate_prepend(errp, local_err,
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"failed to create frontend: ");
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return;
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}
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xendev->frontend_state_watch =
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xen_bus_add_watch(xenbus, xendev->frontend_path, "state",
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xen_device_frontend_changed, xendev, &local_err);
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if (local_err) {
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error_propagate_prepend(errp, local_err,
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"failed to watch frontend state: ");
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}
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}
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@ -262,6 +464,11 @@ static void xen_device_frontend_destroy(XenDevice *xendev)
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XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
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Error *local_err = NULL;
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if (xendev->frontend_state_watch) {
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xen_bus_remove_watch(xenbus, xendev->frontend_state_watch, NULL);
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xendev->frontend_state_watch = NULL;
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}
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if (!xendev->frontend_path) {
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return;
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}
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