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.durr...@citrix.com> --- Cc: Kevin Wolf <kw...@redhat.com> Cc: Max Reitz <mre...@redhat.com> Cc: Stefano Stabellini <sstabell...@kernel.org> Cc: Anthony Perard <anthony.per...@citrix.com> v3: - Remove unnecessary instances of local_err 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 | 70 +++++++++++++ hw/xen/trace-events | 6 ++ hw/xen/xen-bus-helper.c | 34 +++++++ hw/xen/xen-bus.c | 211 +++++++++++++++++++++++++++++++++++++++- include/hw/xen/xen-bus-helper.h | 6 ++ include/hw/xen/xen-bus.h | 15 +++ 7 files changed, 342 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 fa57bf1..5932672 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); @@ -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; 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 15b3ad8..5f7a4b2 100644 --- a/hw/xen/xen-bus-helper.c +++ b/hw/xen/xen-bus-helper.c @@ -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); +} diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 843fda2..5e19592 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 +61,87 @@ 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: @@ -139,8 +249,25 @@ 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, 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; } diff --git a/include/hw/xen/xen-bus-helper.h b/include/hw/xen/xen-bus-helper.h index 5cd9c3d..4c0f747 100644 --- a/include/hw/xen/xen-bus-helper.h +++ b/include/hw/xen/xen-bus-helper.h @@ -36,4 +36,10 @@ int xs_node_scanf(struct xs_handle *xsh, xs_transaction_t tid, 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