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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 05/18] 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@xxxxxxxxxx>
---
Cc: Kevin Wolf <kwolf@xxxxxxxxxx>
Cc: Max Reitz <mreitz@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
v2:
- Don't crash when xen_block_disconnect() fails
- Check xs_unwatch() for error
- Add new_watch() and free_watch() utility functions
- Use xs_check_watch() rather than xs_read_watch()
---
hw/block/trace-events | 2 +
hw/block/xen-block.c | 73 ++++++++++++++
hw/xen/trace-events | 6 ++
hw/xen/xen-bus-helper.c | 34 +++++++
hw/xen/xen-bus.c | 217 +++++++++++++++++++++++++++++++++++++++-
include/hw/xen/xen-bus-helper.h | 6 ++
include/hw/xen/xen-bus.h | 15 +++
7 files changed, 351 insertions(+), 2 deletions(-)
diff --git a/hw/block/trace-events b/hw/block/trace-events
index 4afbd62..89e2583 100644
--- a/hw/block/trace-events
+++ b/hw/block/trace-events
@@ -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) ""
diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index 440bec2..d2334ef 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -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->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->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);
@@ -36,6 +54,12 @@ 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, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ }
+
if (blockdev_class->unrealize) {
blockdev_class->unrealize(blockdev, &local_err);
if (local_err) {
@@ -68,6 +92,54 @@ 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) ?
@@ -276,6 +348,7 @@ 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;
diff --git a/hw/xen/trace-events b/hw/xen/trace-events
index 75dc226..22055b5 100644
--- a/hw/xen/trace-events
+++ b/hw/xen/trace-events
@@ -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"
diff --git a/hw/xen/xen-bus-helper.c b/hw/xen/xen-bus-helper.c
index 2304f8e..d1d5512 100644
--- a/hw/xen/xen-bus-helper.c
+++ b/hw/xen/xen-bus-helper.c
@@ -145,3 +145,37 @@ int xs_node_scanf(struct xs_handle *xsh, const char *node,
const char *key,
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);
+}
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index 3bd5e4e..f0732f8 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -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 +61,93 @@ 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)
+{
+ Error *local_err = NULL;
+
+ trace_xen_bus_remove_watch(watch->node, watch->key, watch->token);
+
+ xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token,
+ &local_err);
+
+ notifier_remove(&watch->notifier);
+ free_watch(watch);
+
+ if (local_err) {
+ error_propagate(errp, local_err);
+ }
+}
+
static void xen_bus_unrealize(BusState *bus, Error **errp)
{
XenBus *xenbus = XEN_BUS(bus);
@@ -69,9 +158,33 @@ 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 +205,9 @@ 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:
@@ -139,8 +255,25 @@ static void xen_device_backend_printf(XenDevice *xendev,
const char *key,
}
}
-static void xen_device_backend_set_state(XenDevice *xendev,
- enum xenbus_state state)
+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, 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 +288,11 @@ 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)));
@@ -217,6 +355,23 @@ 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, 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)
{
@@ -233,6 +388,50 @@ 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)));
@@ -253,6 +452,15 @@ 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: ");
}
}
@@ -261,6 +469,11 @@ 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;
}
diff --git a/include/hw/xen/xen-bus-helper.h b/include/hw/xen/xen-bus-helper.h
index 083e4de..57935ff 100644
--- a/include/hw/xen/xen-bus-helper.h
+++ b/include/hw/xen/xen-bus-helper.h
@@ -31,4 +31,10 @@ int xs_node_vscanf(struct xs_handle *xsh, const char *node,
const char *key,
int xs_node_scanf(struct xs_handle *xsh, const char *node, const char *key,
Error **errp, const char *fmt, ...);
+/* Watch node/key unless node is empty, in which case watch key */
+void xs_node_watch(struct xs_handle *xsh, const char *node, const char *key,
+ char *token, Error **errp);
+void xs_node_unwatch(struct xs_handle *xsh, const char *node, const char *key,
+ const char *token, Error **errp);
+
#endif /* HW_XEN_BUS_HELPER_H */
diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h
index 85a75d8..df73674 100644
--- a/include/hw/xen/xen-bus.h
+++ b/include/hw/xen/xen-bus.h
@@ -10,6 +10,11 @@
#include "hw/xen/xen_common.h"
#include "hw/sysbus.h"
+#include "qemu/notify.h"
+
+typedef void (*XenWatchHandler)(void *opaque);
+
+typedef struct XenWatch XenWatch;
typedef struct XenDevice {
DeviceState qdev;
@@ -18,10 +23,14 @@ typedef struct XenDevice {
char *backend_path, *frontend_path;
enum xenbus_state backend_state, frontend_state;
Notifier exit;
+ XenWatch *frontend_state_watch;
} XenDevice;
typedef char *(*XenDeviceGetName)(XenDevice *xendev, Error **errp);
typedef void (*XenDeviceRealize)(XenDevice *xendev, Error **errp);
+typedef void (*XenDeviceFrontendChanged)(XenDevice *xendev,
+ enum xenbus_state frontend_state,
+ Error **errp);
typedef void (*XenDeviceUnrealize)(XenDevice *xendev, Error **errp);
typedef struct XenDeviceClass {
@@ -32,6 +41,7 @@ typedef struct XenDeviceClass {
const char *device;
XenDeviceGetName get_name;
XenDeviceRealize realize;
+ XenDeviceFrontendChanged frontend_changed;
XenDeviceUnrealize unrealize;
} XenDeviceClass;
@@ -47,6 +57,7 @@ typedef struct XenBus {
BusState qbus;
domid_t backend_id;
struct xs_handle *xsh;
+ NotifierList watch_notifiers;
} XenBus;
typedef struct XenBusClass {
@@ -64,4 +75,8 @@ typedef struct XenBusClass {
void xen_bus_init(void);
+void xen_device_backend_set_state(XenDevice *xendev,
+ enum xenbus_state state);
+enum xenbus_state xen_device_backend_get_state(XenDevice *xendev);
+
#endif /* HW_XEN_BUS_H */
--
2.1.4
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