From df6180bb56cd03949c2c64083da58755fed81a61 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Tue, 10 Sep 2019 18:17:53 +0100 Subject: [PATCH 1/7] xen-bus: check whether the frontend is active during device reset... ...not the backend Commit cb323146 "xen-bus: Fix backend state transition on device reset" contained a subtle mistake. The hunk @@ -539,11 +556,11 @@ static void xen_device_backend_changed(void *opaque) /* * If the toolstack (or unplug request callback) has set the backend - * state to Closing, but there is no active frontend (i.e. the - * state is not Connected) then set the backend state to Closed. + * state to Closing, but there is no active frontend then set the + * backend state to Closed. */ if (xendev->backend_state == XenbusStateClosing && - xendev->frontend_state != XenbusStateConnected) { + !xen_device_state_is_active(state)) { xen_device_backend_set_state(xendev, XenbusStateClosed); } mistakenly replaced the check of 'xendev->frontend_state' with a check (now in a helper function) of 'state', which actually equates to 'xendev->backend_state'. This patch fixes the mistake. Fixes: cb3231460747552d70af9d546dc53d8195bcb796 Signed-off-by: Paul Durrant Reviewed-by: Anthony PERARD Message-Id: <20190910171753.3775-1-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/xen/xen-bus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index a04478ad4f..025df5e59f 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -560,7 +560,7 @@ static void xen_device_backend_changed(void *opaque) * backend state to Closed. */ if (xendev->backend_state == XenbusStateClosing && - !xen_device_state_is_active(state)) { + !xen_device_state_is_active(xendev->frontend_state)) { xen_device_backend_set_state(xendev, XenbusStateClosed); } From 374752a26b0ea487dd49c638ee35b97a58ce8e3b Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Fri, 13 Sep 2019 09:21:56 +0100 Subject: [PATCH 2/7] xen / notify: introduce a new XenWatchList abstraction Xenstore watch call-backs are already abstracted away from XenBus using the XenWatch data structure but the associated NotifierList manipulation and file handle registration is still open coded in various xen_bus_...() functions. This patch creates a new XenWatchList data structure to allow these interactions to be abstracted away from XenBus as well. This is in preparation for a subsequent patch which will introduce separate watch lists for XenBus and XenDevice objects. NOTE: This patch also introduces a new notifier_list_empty() helper function for the purposes of adding an assertion that a XenWatchList is not freed whilst its associated NotifierList is still occupied. Signed-off-by: Paul Durrant Reviewed-by: Anthony Perard Message-Id: <20190913082159.31338-2-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/xen/trace-events | 5 +- hw/xen/xen-bus.c | 117 +++++++++++++++++++++++++-------------- include/hw/xen/xen-bus.h | 3 +- include/qemu/notify.h | 2 + util/notify.c | 5 ++ 5 files changed, 87 insertions(+), 45 deletions(-) diff --git a/hw/xen/trace-events b/hw/xen/trace-events index bc82ecb1a5..ac8d9c20d2 100644 --- a/hw/xen/trace-events +++ b/hw/xen/trace-events @@ -19,9 +19,8 @@ xen_bus_unrealize(void) "" xen_bus_enumerate(void) "" xen_bus_type_enumerate(const char *type) "type: %s" xen_bus_backend_create(const char *type, const char *path) "type: %s path: %s" -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_bus_add_watch(const char *node, const char *key) "node: %s key: %s" +xen_bus_remove_watch(const char *node, const char *key) "node: %s key: %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" diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 025df5e59f..28efaccff2 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -157,18 +157,60 @@ static void free_watch(XenWatch *watch) g_free(watch); } -static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, - const char *key, XenWatchHandler handler, - void *opaque, Error **errp) +struct XenWatchList { + struct xs_handle *xsh; + NotifierList notifiers; +}; + +static void watch_list_event(void *opaque) +{ + XenWatchList *watch_list = opaque; + char **v; + const char *token; + + v = xs_check_watch(watch_list->xsh); + if (!v) { + return; + } + + token = v[XS_WATCH_TOKEN]; + + notifier_list_notify(&watch_list->notifiers, (void *)token); + + free(v); +} + +static XenWatchList *watch_list_create(struct xs_handle *xsh) +{ + XenWatchList *watch_list = g_new0(XenWatchList, 1); + + g_assert(xsh); + + watch_list->xsh = xsh; + notifier_list_init(&watch_list->notifiers); + qemu_set_fd_handler(xs_fileno(watch_list->xsh), watch_list_event, NULL, + watch_list); + + return watch_list; +} + +static void watch_list_destroy(XenWatchList *watch_list) +{ + g_assert(notifier_list_empty(&watch_list->notifiers)); + qemu_set_fd_handler(xs_fileno(watch_list->xsh), NULL, NULL, NULL); + g_free(watch_list); +} + +static XenWatch *watch_list_add(XenWatchList *watch_list, 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(&watch_list->notifiers, &watch->notifier); - notifier_list_add(&xenbus->watch_notifiers, &watch->notifier); - - xs_node_watch(xenbus->xsh, node, key, watch->token, &local_err); + xs_node_watch(watch_list->xsh, node, key, watch->token, &local_err); if (local_err) { error_propagate(errp, local_err); @@ -181,18 +223,34 @@ static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, return watch; } -static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch, - Error **errp) +static void watch_list_remove(XenWatchList *watch_list, 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, + xs_node_unwatch(watch_list->xsh, watch->node, watch->key, watch->token, errp); notifier_remove(&watch->notifier); free_watch(watch); } +static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, + const char *key, XenWatchHandler handler, + void *opaque, Error **errp) +{ + trace_xen_bus_add_watch(node, key); + + return watch_list_add(xenbus->watch_list, node, key, handler, opaque, + errp); +} + +static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch, + Error **errp) +{ + trace_xen_bus_remove_watch(watch->node, watch->key); + + watch_list_remove(xenbus->watch_list, watch, errp); +} + static void xen_bus_backend_create(XenBus *xenbus, const char *type, const char *name, char *path, Error **errp) @@ -338,35 +396,14 @@ static void xen_bus_unrealize(BusState *bus, Error **errp) xenbus->backend_watch = NULL; } - if (!xenbus->xsh) { - return; + if (xenbus->watch_list) { + watch_list_destroy(xenbus->watch_list); + xenbus->watch_list = NULL; } - 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; + if (xenbus->xsh) { + xs_close(xenbus->xsh); } - - 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) @@ -390,9 +427,7 @@ 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); + xenbus->watch_list = watch_list_create(xenbus->xsh); module_call_init(MODULE_INIT_XEN_BACKEND); diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h index 1c2d9dfdb8..88b84e29bb 100644 --- a/include/hw/xen/xen-bus.h +++ b/include/hw/xen/xen-bus.h @@ -14,6 +14,7 @@ typedef void (*XenWatchHandler)(void *opaque); +typedef struct XenWatchList XenWatchList; typedef struct XenWatch XenWatch; typedef struct XenEventChannel XenEventChannel; @@ -63,7 +64,7 @@ typedef struct XenBus { BusState qbus; domid_t backend_id; struct xs_handle *xsh; - NotifierList watch_notifiers; + XenWatchList *watch_list; XenWatch *backend_watch; } XenBus; diff --git a/include/qemu/notify.h b/include/qemu/notify.h index a3d73e4bc7..bcfa70fb2e 100644 --- a/include/qemu/notify.h +++ b/include/qemu/notify.h @@ -40,6 +40,8 @@ void notifier_remove(Notifier *notifier); void notifier_list_notify(NotifierList *list, void *data); +bool notifier_list_empty(NotifierList *list); + /* Same as Notifier but allows .notify() to return errors */ typedef struct NotifierWithReturn NotifierWithReturn; diff --git a/util/notify.c b/util/notify.c index aee8d93cb0..76bab212ae 100644 --- a/util/notify.c +++ b/util/notify.c @@ -40,6 +40,11 @@ void notifier_list_notify(NotifierList *list, void *data) } } +bool notifier_list_empty(NotifierList *list) +{ + return QLIST_EMPTY(&list->notifiers); +} + void notifier_with_return_list_init(NotifierWithReturnList *list) { QLIST_INIT(&list->notifiers); From d198b711f9ff9032d7270d78d5b5b17abf740e75 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Fri, 13 Sep 2019 09:21:57 +0100 Subject: [PATCH 3/7] xen: introduce separate XenWatchList for XenDevice objects This patch uses the XenWatchList abstraction to add a separate watch list for each device. This is more scalable than walking a single notifier list for all watches and is also necessary to implement a bug-fix in a subsequent patch. Signed-off-by: Paul Durrant Reviewed-by: Anthony Perard Message-Id: <20190913082159.31338-3-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/xen/trace-events | 2 ++ hw/xen/xen-bus.c | 72 ++++++++++++++++++++++++++++++++-------- include/hw/xen/xen-bus.h | 2 ++ 3 files changed, 62 insertions(+), 14 deletions(-) diff --git a/hw/xen/trace-events b/hw/xen/trace-events index ac8d9c20d2..80ce3dafad 100644 --- a/hw/xen/trace-events +++ b/hw/xen/trace-events @@ -29,6 +29,8 @@ xen_device_backend_changed(const char *type, char *name) "type: %s name: %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" xen_device_unplug(const char *type, char *name) "type: %s name: %s" +xen_device_add_watch(const char *type, char *name, const char *node, const char *key) "type: %s name: %s node: %s key: %s" +xen_device_remove_watch(const char *type, char *name, const char *node, const char *key) "type: %s name: %s node: %s key: %s" # xen-bus-helper.c xs_node_create(const char *node) "%s" diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 28efaccff2..810a4e2df3 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -235,11 +235,11 @@ static void watch_list_remove(XenWatchList *watch_list, XenWatch *watch, static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, const char *key, XenWatchHandler handler, - void *opaque, Error **errp) + Error **errp) { trace_xen_bus_add_watch(node, key); - return watch_list_add(xenbus->watch_list, node, key, handler, opaque, + return watch_list_add(xenbus->watch_list, node, key, handler, xenbus, errp); } @@ -433,7 +433,7 @@ static void xen_bus_realize(BusState *bus, Error **errp) xenbus->backend_watch = xen_bus_add_watch(xenbus, "", /* domain root node */ - "backend", xen_bus_enumerate, xenbus, &local_err); + "backend", xen_bus_enumerate, &local_err); if (local_err) { /* This need not be treated as a hard error so don't propagate */ error_reportf_err(local_err, @@ -621,6 +621,31 @@ static void xen_device_backend_changed(void *opaque) } } +static XenWatch *xen_device_add_watch(XenDevice *xendev, const char *node, + const char *key, + XenWatchHandler handler, + Error **errp) +{ + const char *type = object_get_typename(OBJECT(xendev)); + + trace_xen_device_add_watch(type, xendev->name, node, key); + + return watch_list_add(xendev->watch_list, node, key, handler, xendev, + errp); +} + +static void xen_device_remove_watch(XenDevice *xendev, XenWatch *watch, + Error **errp) +{ + const char *type = object_get_typename(OBJECT(xendev)); + + trace_xen_device_remove_watch(type, xendev->name, watch->node, + watch->key); + + watch_list_remove(xendev->watch_list, watch, errp); +} + + static void xen_device_backend_create(XenDevice *xendev, Error **errp) { XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev))); @@ -645,9 +670,9 @@ static void xen_device_backend_create(XenDevice *xendev, Error **errp) } xendev->backend_state_watch = - xen_bus_add_watch(xenbus, xendev->backend_path, - "state", xen_device_backend_changed, - xendev, &local_err); + xen_device_add_watch(xendev, xendev->backend_path, + "state", xen_device_backend_changed, + &local_err); if (local_err) { error_propagate_prepend(errp, local_err, "failed to watch backend state: "); @@ -655,9 +680,9 @@ static void xen_device_backend_create(XenDevice *xendev, Error **errp) } xendev->backend_online_watch = - xen_bus_add_watch(xenbus, xendev->backend_path, - "online", xen_device_backend_changed, - xendev, &local_err); + xen_device_add_watch(xendev, xendev->backend_path, + "online", xen_device_backend_changed, + &local_err); if (local_err) { error_propagate_prepend(errp, local_err, "failed to watch backend online: "); @@ -671,12 +696,12 @@ static void xen_device_backend_destroy(XenDevice *xendev) Error *local_err = NULL; if (xendev->backend_online_watch) { - xen_bus_remove_watch(xenbus, xendev->backend_online_watch, NULL); + xen_device_remove_watch(xendev, xendev->backend_online_watch, NULL); xendev->backend_online_watch = NULL; } if (xendev->backend_state_watch) { - xen_bus_remove_watch(xenbus, xendev->backend_state_watch, NULL); + xen_device_remove_watch(xendev, xendev->backend_state_watch, NULL); xendev->backend_state_watch = NULL; } @@ -812,8 +837,8 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp) } xendev->frontend_state_watch = - xen_bus_add_watch(xenbus, xendev->frontend_path, "state", - xen_device_frontend_changed, xendev, &local_err); + xen_device_add_watch(xendev, xendev->frontend_path, "state", + xen_device_frontend_changed, &local_err); if (local_err) { error_propagate_prepend(errp, local_err, "failed to watch frontend state: "); @@ -826,7 +851,8 @@ static void xen_device_frontend_destroy(XenDevice *xendev) Error *local_err = NULL; if (xendev->frontend_state_watch) { - xen_bus_remove_watch(xenbus, xendev->frontend_state_watch, NULL); + xen_device_remove_watch(xendev, xendev->frontend_state_watch, + NULL); xendev->frontend_state_watch = NULL; } @@ -1122,6 +1148,16 @@ static void xen_device_unrealize(DeviceState *dev, Error **errp) xendev->xgth = NULL; } + if (xendev->watch_list) { + watch_list_destroy(xendev->watch_list); + xendev->watch_list = NULL; + } + + if (xendev->xsh) { + xs_close(xendev->xsh); + xendev->xsh = NULL; + } + g_free(xendev->name); xendev->name = NULL; } @@ -1164,6 +1200,14 @@ static void xen_device_realize(DeviceState *dev, Error **errp) trace_xen_device_realize(type, xendev->name); + xendev->xsh = xs_open(0); + if (!xendev->xsh) { + error_setg_errno(errp, errno, "failed xs_open"); + goto unrealize; + } + + xendev->watch_list = watch_list_create(xendev->xsh); + xendev->xgth = xengnttab_open(NULL, 0); if (!xendev->xgth) { error_setg_errno(errp, errno, "failed xengnttab_open"); diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h index 88b84e29bb..0d198148f6 100644 --- a/include/hw/xen/xen-bus.h +++ b/include/hw/xen/xen-bus.h @@ -22,6 +22,8 @@ typedef struct XenDevice { DeviceState qdev; domid_t frontend_id; char *name; + struct xs_handle *xsh; + XenWatchList *watch_list; char *backend_path, *frontend_path; enum xenbus_state backend_state, frontend_state; Notifier exit; From 3809f7583ba463b9877755e6ca5f5f036430fdda Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Fri, 13 Sep 2019 09:21:58 +0100 Subject: [PATCH 4/7] xen: perform XenDevice clean-up in XenBus watch handler Cleaning up offline XenDevice objects directly in xen_device_backend_changed() is dangerous as xen_device_unrealize() will modify the watch list that is being walked. Even the QLIST_FOREACH_SAFE() used in notifier_list_notify() is insufficient as *two* notifiers (for the frontend and backend watches) are removed, thus potentially rendering the 'next' pointer unsafe. The solution is to use the XenBus backend_watch handler to do the clean-up instead, as it is invoked whilst walking a separate watch list. This patch therefore adds a new 'inactive_devices' list to XenBus, to which offline devices are added by xen_device_backend_changed(). The XenBus backend_watch registration is also changed to not only invoke xen_bus_enumerate() but also a new xen_bus_cleanup() function, which will walk 'inactive_devices' and perform the necessary actions. For safety an extra 'online' check is also added to xen_bus_type_enumerate() to make sure that no attempt is made to create a new XenDevice object for a backend that is offline. NOTE: This patch also includes some cosmetic changes: - substitute the local variable name 'backend_state' in xen_bus_type_enumerate() with 'state', since there is no ambiguity with any other state in that context. - change xen_device_state_is_active() to xen_device_frontend_is_active() (and pass a XenDevice directly) since the state tests contained therein only apply to a frontend. - use 'state' rather then 'xendev->backend_state' in xen_device_backend_changed() to shorten the code. Signed-off-by: Paul Durrant Reviewed-by: Anthony PERARD Message-Id: <20190913082159.31338-4-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/xen/trace-events | 2 + hw/xen/xen-bus.c | 94 +++++++++++++++++++++++++++++----------- include/hw/xen/xen-bus.h | 3 ++ 3 files changed, 74 insertions(+), 25 deletions(-) diff --git a/hw/xen/trace-events b/hw/xen/trace-events index 80ce3dafad..e6885bc751 100644 --- a/hw/xen/trace-events +++ b/hw/xen/trace-events @@ -17,8 +17,10 @@ xen_domid_restrict(int err) "err: %u" xen_bus_realize(void) "" xen_bus_unrealize(void) "" xen_bus_enumerate(void) "" +xen_bus_cleanup(void) "" xen_bus_type_enumerate(const char *type) "type: %s" xen_bus_backend_create(const char *type, const char *path) "type: %s path: %s" +xen_bus_device_cleanup(const char *type, char *name) "type: %s name: %s" xen_bus_add_watch(const char *node, const char *key) "node: %s key: %s" xen_bus_remove_watch(const char *node, const char *key) "node: %s key: %s" xen_device_realize(const char *type, char *name) "type: %s name: %s" diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 810a4e2df3..55c157393d 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -340,13 +340,18 @@ static void xen_bus_type_enumerate(XenBus *xenbus, const char *type) for (i = 0; i < n; i++) { char *backend_path = g_strdup_printf("%s/%s", domain_path, backend[i]); - enum xenbus_state backend_state; + enum xenbus_state state; + unsigned int online; if (xs_node_scanf(xenbus->xsh, XBT_NULL, backend_path, "state", - NULL, "%u", &backend_state) != 1) - backend_state = XenbusStateUnknown; + NULL, "%u", &state) != 1) + state = XenbusStateUnknown; - if (backend_state == XenbusStateInitialising) { + if (xs_node_scanf(xenbus->xsh, XBT_NULL, backend_path, "online", + NULL, "%u", &online) != 1) + online = 0; + + if (online && state == XenbusStateInitialising) { Error *local_err = NULL; xen_bus_backend_create(xenbus, type, backend[i], backend_path, @@ -365,9 +370,8 @@ out: g_free(domain_path); } -static void xen_bus_enumerate(void *opaque) +static void xen_bus_enumerate(XenBus *xenbus) { - XenBus *xenbus = opaque; char **type; unsigned int i, n; @@ -385,6 +389,45 @@ static void xen_bus_enumerate(void *opaque) free(type); } +static void xen_bus_device_cleanup(XenDevice *xendev) +{ + const char *type = object_get_typename(OBJECT(xendev)); + Error *local_err = NULL; + + trace_xen_bus_device_cleanup(type, xendev->name); + + g_assert(!xendev->backend_online); + + if (!xen_backend_try_device_destroy(xendev, &local_err)) { + object_unparent(OBJECT(xendev)); + } + + if (local_err) { + error_report_err(local_err); + } +} + +static void xen_bus_cleanup(XenBus *xenbus) +{ + XenDevice *xendev, *next; + + trace_xen_bus_cleanup(); + + QLIST_FOREACH_SAFE(xendev, &xenbus->inactive_devices, list, next) { + g_assert(xendev->inactive); + QLIST_REMOVE(xendev, list); + xen_bus_device_cleanup(xendev); + } +} + +static void xen_bus_backend_changed(void *opaque) +{ + XenBus *xenbus = opaque; + + xen_bus_enumerate(xenbus); + xen_bus_cleanup(xenbus); +} + static void xen_bus_unrealize(BusState *bus, Error **errp) { XenBus *xenbus = XEN_BUS(bus); @@ -433,7 +476,7 @@ static void xen_bus_realize(BusState *bus, Error **errp) xenbus->backend_watch = xen_bus_add_watch(xenbus, "", /* domain root node */ - "backend", xen_bus_enumerate, &local_err); + "backend", xen_bus_backend_changed, &local_err); if (local_err) { /* This need not be treated as a hard error so don't propagate */ error_reportf_err(local_err, @@ -555,9 +598,9 @@ static void xen_device_backend_set_online(XenDevice *xendev, bool online) * Tell from the state whether the frontend is likely alive, * i.e. it will react to a change of state of the backend. */ -static bool xen_device_state_is_active(enum xenbus_state state) +static bool xen_device_frontend_is_active(XenDevice *xendev) { - switch (state) { + switch (xendev->frontend_state) { case XenbusStateInitWait: case XenbusStateInitialised: case XenbusStateConnected: @@ -594,30 +637,31 @@ static void xen_device_backend_changed(void *opaque) * state to Closing, but there is no active frontend then set the * backend state to Closed. */ - if (xendev->backend_state == XenbusStateClosing && - !xen_device_state_is_active(xendev->frontend_state)) { + if (state == XenbusStateClosing && + !xen_device_frontend_is_active(xendev)) { xen_device_backend_set_state(xendev, XenbusStateClosed); } /* * If a backend is still 'online' then we should leave it alone but, - * if a backend is not 'online', then the device should be destroyed - * once the state is Closed. + * if a backend is not 'online', then the device is a candidate + * for destruction. Hence add it to the 'inactive' list to be cleaned + * by xen_bus_cleanup(). */ - if (!xendev->backend_online && - (xendev->backend_state == XenbusStateClosed || - xendev->backend_state == XenbusStateInitialising || - xendev->backend_state == XenbusStateInitWait || - xendev->backend_state == XenbusStateUnknown)) { - Error *local_err = NULL; + if (!online && + (state == XenbusStateClosed || state == XenbusStateInitialising || + state == XenbusStateInitWait || state == XenbusStateUnknown) && + !xendev->inactive) { + XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev))); - if (!xen_backend_try_device_destroy(xendev, &local_err)) { - object_unparent(OBJECT(xendev)); - } + xendev->inactive = true; + QLIST_INSERT_HEAD(&xenbus->inactive_devices, xendev, list); - if (local_err) { - error_report_err(local_err); - } + /* + * Re-write the state to cause a XenBus backend_watch notification, + * resulting in a call to xen_bus_cleanup(). + */ + xen_device_backend_printf(xendev, "state", "%u", state); } } diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h index 0d198148f6..3d5532258d 100644 --- a/include/hw/xen/xen-bus.h +++ b/include/hw/xen/xen-bus.h @@ -32,7 +32,9 @@ typedef struct XenDevice { XenWatch *backend_online_watch; xengnttab_handle *xgth; bool feature_grant_copy; + bool inactive; QLIST_HEAD(, XenEventChannel) event_channels; + QLIST_ENTRY(XenDevice) list; } XenDevice; typedef char *(*XenDeviceGetName)(XenDevice *xendev, Error **errp); @@ -68,6 +70,7 @@ typedef struct XenBus { struct xs_handle *xsh; XenWatchList *watch_list; XenWatch *backend_watch; + QLIST_HEAD(, XenDevice) inactive_devices; } XenBus; typedef struct XenBusClass { From 784e9727af98f789498afb4c7a526e8de19d8b6d Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Fri, 13 Sep 2019 13:24:18 +0100 Subject: [PATCH 5/7] MAINTAINERS: update my email address My Citrix email address will expire shortly. Signed-off-by: Paul Durrant Reviewed-by: Anthony PERARD Message-Id: <20190913122418.848-1-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- MAINTAINERS | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index 1c56d45b16..bd7ee23101 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -406,7 +406,7 @@ Guest CPU Cores (Xen) X86 Xen CPUs M: Stefano Stabellini M: Anthony Perard -M: Paul Durrant +M: Paul Durrant L: xen-devel@lists.xenproject.org S: Supported F: */xen* From ef916ab3ec570eac799be540e499d0123fe61899 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Wed, 18 Sep 2019 12:57:02 +0100 Subject: [PATCH 6/7] xen-block: treat XenbusStateUnknown the same as XenbusStateClosed When a frontend gracefully disconnects from an offline backend, it will set its own state to XenbusStateClosed. The code in xen-block.c correctly deals with this and sets the backend into XenbusStateClosed. Unfortunately it is possible for toolstack to actually delete the frontend area before the state key has been read, leading to an apparent frontend state of XenbusStateUnknown. This prevents the backend state from transitioning to XenbusStateClosed and hence leaves it limbo. This patch simply treats a frontend state of XenbusStateUnknown the same as XenbusStateClosed, which will unblock the backend in these circumstances. Reported-by: Mark Syms Signed-off-by: Paul Durrant Acked-by: Anthony PERARD Reviewed-by: John Snow Message-Id: <20190918115702.38959-1-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/block/xen-block.c | 1 + 1 file changed, 1 insertion(+) diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c index f77343db60..879fc310a4 100644 --- a/hw/block/xen-block.c +++ b/hw/block/xen-block.c @@ -313,6 +313,7 @@ static void xen_block_frontend_changed(XenDevice *xendev, break; case XenbusStateClosed: + case XenbusStateUnknown: xen_block_disconnect(xendev, &local_err); if (local_err) { error_propagate(errp, local_err); From 6bd6b955c0b2666263700d39db153ab43c5e0c9e Mon Sep 17 00:00:00 2001 From: Mark Syms Date: Wed, 18 Sep 2019 12:57:44 +0100 Subject: [PATCH 7/7] xen-bus: only set the xen device frontend state if it is missing Some toolstack implementations will set the frontend xenstore keys to Initialising which will then trigger the in guest PV drivers to begin initialising and some implementations will then set their state to Closing. If this has occurred then device realize must not overwrite the frontend keys as then the handshake will stall. Signed-off-by: Mark Syms Also avoid creating the frontend area if it already exists. Signed-off-by: Paul Durrant Reviewed-by: Anthony PERARD Message-Id: <20190918115745.39006-1-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/xen/xen-bus.c | 47 +++++++++++++++++++++++++++++++---------------- 1 file changed, 31 insertions(+), 16 deletions(-) diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 55c157393d..c2ad22a42d 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -857,6 +857,13 @@ static void xen_device_frontend_changed(void *opaque) } } +static bool xen_device_frontend_exists(XenDevice *xendev) +{ + enum xenbus_state state; + + return (xen_device_frontend_scanf(xendev, "state", "%u", &state) == 1); +} + static void xen_device_frontend_create(XenDevice *xendev, Error **errp) { XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev))); @@ -865,19 +872,25 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp) xendev->frontend_path = xen_device_get_frontend_path(xendev); - perms[0].id = xendev->frontend_id; - perms[0].perms = XS_PERM_NONE; - perms[1].id = xenbus->backend_id; - perms[1].perms = XS_PERM_READ | XS_PERM_WRITE; + /* + * The frontend area may have already been created by a legacy + * toolstack. + */ + if (!xen_device_frontend_exists(xendev)) { + perms[0].id = xendev->frontend_id; + perms[0].perms = XS_PERM_NONE; + perms[1].id = xenbus->backend_id; + perms[1].perms = XS_PERM_READ | XS_PERM_WRITE; - g_assert(xenbus->xsh); + g_assert(xenbus->xsh); - xs_node_create(xenbus->xsh, XBT_NULL, xendev->frontend_path, perms, - ARRAY_SIZE(perms), &local_err); - if (local_err) { - error_propagate_prepend(errp, local_err, - "failed to create frontend: "); - return; + xs_node_create(xenbus->xsh, XBT_NULL, xendev->frontend_path, perms, + ARRAY_SIZE(perms), &local_err); + if (local_err) { + error_propagate_prepend(errp, local_err, + "failed to create frontend: "); + return; + } } xendev->frontend_state_watch = @@ -1290,12 +1303,14 @@ static void xen_device_realize(DeviceState *dev, Error **errp) xen_device_backend_set_online(xendev, true); xen_device_backend_set_state(xendev, XenbusStateInitWait); - xen_device_frontend_printf(xendev, "backend", "%s", - xendev->backend_path); - xen_device_frontend_printf(xendev, "backend-id", "%u", - xenbus->backend_id); + if (!xen_device_frontend_exists(xendev)) { + xen_device_frontend_printf(xendev, "backend", "%s", + xendev->backend_path); + xen_device_frontend_printf(xendev, "backend-id", "%u", + xenbus->backend_id); - xen_device_frontend_set_state(xendev, XenbusStateInitialising, true); + xen_device_frontend_set_state(xendev, XenbusStateInitialising, true); + } xendev->exit.notify = xen_device_exit; qemu_add_exit_notifier(&xendev->exit);