xen-bus: reduce scope of backend watch
Currently a single watch on /local/domain/X/backend is registered by each QEMU process running in service domain X (where X is usually 0). The purpose of this watch is to ensure that QEMU is notified when the Xen toolstack creates a new device backend area. Such a backend area is specific to a single frontend area created for a specific guest domain and, since each QEMU process is also created to service a specfic guest domain, it is unnecessary and inefficient to notify all QEMU processes. Only the QEMU process associated with the same guest domain need receive the notification. This patch re-factors the watch registration code such that notifications are targetted appropriately. Reported-by: Jerome Leseinne <jerome.leseinne@gmail.com> Signed-off-by: Paul Durrant <pdurrant@amazon.com> Reviewed-by: Anthony PERARD <anthony.perard@citrix.com> Message-Id: <20201001081500.1026-1-paul@xen.org> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
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@ -41,6 +41,12 @@ static void xen_backend_table_add(XenBackendImpl *impl)
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g_hash_table_insert(xen_backend_table_get(), (void *)impl->type, impl);
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g_hash_table_insert(xen_backend_table_get(), (void *)impl->type, impl);
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}
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}
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static const char **xen_backend_table_keys(unsigned int *count)
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{
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return (const char **)g_hash_table_get_keys_as_array(
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xen_backend_table_get(), count);
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}
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static const XenBackendImpl *xen_backend_table_lookup(const char *type)
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static const XenBackendImpl *xen_backend_table_lookup(const char *type)
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{
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{
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return g_hash_table_lookup(xen_backend_table_get(), type);
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return g_hash_table_lookup(xen_backend_table_get(), type);
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@ -70,6 +76,11 @@ void xen_backend_register(const XenBackendInfo *info)
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xen_backend_table_add(impl);
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xen_backend_table_add(impl);
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}
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}
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const char **xen_backend_get_types(unsigned int *count)
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{
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return xen_backend_table_keys(count);
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}
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static QLIST_HEAD(, XenBackendInstance) backend_list;
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static QLIST_HEAD(, XenBackendInstance) backend_list;
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static void xen_backend_list_add(XenBackendInstance *backend)
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static void xen_backend_list_add(XenBackendInstance *backend)
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@ -430,7 +430,15 @@ static void xen_bus_unrealize(BusState *bus)
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trace_xen_bus_unrealize();
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trace_xen_bus_unrealize();
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if (xenbus->backend_watch) {
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if (xenbus->backend_watch) {
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xen_bus_remove_watch(xenbus, xenbus->backend_watch, NULL);
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unsigned int i;
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for (i = 0; i < xenbus->backend_types; i++) {
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if (xenbus->backend_watch[i]) {
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xen_bus_remove_watch(xenbus, xenbus->backend_watch[i], NULL);
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}
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}
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g_free(xenbus->backend_watch);
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xenbus->backend_watch = NULL;
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xenbus->backend_watch = NULL;
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}
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}
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@ -446,8 +454,11 @@ static void xen_bus_unrealize(BusState *bus)
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static void xen_bus_realize(BusState *bus, Error **errp)
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static void xen_bus_realize(BusState *bus, Error **errp)
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{
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{
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char *key = g_strdup_printf("%u", xen_domid);
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XenBus *xenbus = XEN_BUS(bus);
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XenBus *xenbus = XEN_BUS(bus);
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unsigned int domid;
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unsigned int domid;
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const char **type;
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unsigned int i;
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Error *local_err = NULL;
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Error *local_err = NULL;
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trace_xen_bus_realize();
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trace_xen_bus_realize();
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@ -469,19 +480,32 @@ static void xen_bus_realize(BusState *bus, Error **errp)
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module_call_init(MODULE_INIT_XEN_BACKEND);
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module_call_init(MODULE_INIT_XEN_BACKEND);
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xenbus->backend_watch =
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type = xen_backend_get_types(&xenbus->backend_types);
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xen_bus_add_watch(xenbus, "", /* domain root node */
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xenbus->backend_watch = g_new(XenWatch *, xenbus->backend_types);
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"backend", xen_bus_backend_changed, &local_err);
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for (i = 0; i < xenbus->backend_types; i++) {
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char *node = g_strdup_printf("backend/%s", type[i]);
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xenbus->backend_watch[i] =
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xen_bus_add_watch(xenbus, node, key, xen_bus_backend_changed,
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&local_err);
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if (local_err) {
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if (local_err) {
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/* This need not be treated as a hard error so don't propagate */
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/* This need not be treated as a hard error so don't propagate */
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error_reportf_err(local_err,
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error_reportf_err(local_err,
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"failed to set up enumeration watch: ");
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"failed to set up '%s' enumeration watch: ",
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type[i]);
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}
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}
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g_free(node);
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}
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g_free(type);
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g_free(key);
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return;
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return;
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fail:
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fail:
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xen_bus_unrealize(bus);
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xen_bus_unrealize(bus);
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g_free(key);
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}
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}
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static void xen_bus_unplug_request(HotplugHandler *hotplug,
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static void xen_bus_unplug_request(HotplugHandler *hotplug,
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@ -31,6 +31,7 @@ void xen_backend_set_device(XenBackendInstance *backend,
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XenDevice *xen_backend_get_device(XenBackendInstance *backend);
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XenDevice *xen_backend_get_device(XenBackendInstance *backend);
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void xen_backend_register(const XenBackendInfo *info);
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void xen_backend_register(const XenBackendInfo *info);
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const char **xen_backend_get_types(unsigned int *nr);
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void xen_backend_device_create(XenBus *xenbus, const char *type,
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void xen_backend_device_create(XenBus *xenbus, const char *type,
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const char *name, QDict *opts, Error **errp);
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const char *name, QDict *opts, Error **errp);
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@ -66,7 +66,8 @@ struct XenBus {
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domid_t backend_id;
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domid_t backend_id;
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struct xs_handle *xsh;
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struct xs_handle *xsh;
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XenWatchList *watch_list;
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XenWatchList *watch_list;
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XenWatch *backend_watch;
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unsigned int backend_types;
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XenWatch **backend_watch;
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QLIST_HEAD(, XenDevice) inactive_devices;
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QLIST_HEAD(, XenDevice) inactive_devices;
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};
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};
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