| Message ID | 20181121151211.15997-6-paul.durrant@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Xen PV backend 'qdevification' | expand |
On Wed, Nov 21, 2018 at 03:11:58PM +0000, Paul Durrant wrote: > 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-qisk implementation is extended with a 'frontend_changed' method, "The xen-qdisk" > 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> > --- > diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c > index 0859643f7d..35f7b70480 100644 > --- a/hw/block/xen-qdisk.c > +++ b/hw/block/xen-qdisk.c > +static void xen_qdisk_frontend_changed(XenDevice *xendev, > + enum xenbus_state frontend_state, > + Error **errp) > +{ > + XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev); > + 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_qdisk_disconnect(qdiskdev, &error_fatal); Do we want to crash (actually exit) QEMU when disconnect failed? > + xen_qdisk_connect(qdiskdev, &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_qdisk_disconnect(qdiskdev, &error_fatal); > + xen_device_backend_set_state(xendev, XenbusStateClosed); > + break; > + > + default: > + break; > + } > +} > + > diff --git a/hw/xen/xen-bus-helper.c b/hw/xen/xen-bus-helper.c > index d9ee2ed6a0..b44acc8047 100644 > --- a/hw/xen/xen-bus-helper.c > +++ b/hw/xen/xen-bus-helper.c > @@ -122,3 +122,31 @@ 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); > + > + if (!xs_watch(xsh, path, token)) { > + error_setg_errno(errp, errno, "failed to watch path '%s'", path); > + } > + > + g_free(path); > +} > + > +void xs_node_unwatch(struct xs_handle *xsh, const char *node, > + const char *key, const char *token) > +{ > + char *path; > + > + path = (strlen(node) != 0) ? g_strdup_printf("%s/%s", node, key) : > + g_strdup(key); > + > + xs_unwatch(xsh, path, token); I think we should check for error from xs_unwatch as well. > + > + g_free(path); > +} > diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c > index 663aa8e117..99988f8568 100644 > --- a/hw/xen/xen-bus.c > +++ b/hw/xen/xen-bus.c > +static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, > + const char *key, XenWatchHandler handler, > + void *opaque, Error **errp) > +{ > + XenWatch *watch = g_new0(XenWatch, 1); > + QemuUUID uuid; > + Error *local_err = NULL; > + > + qemu_uuid_generate(&uuid); > + watch->token = qemu_uuid_unparse_strdup(&uuid); > + > + trace_xen_bus_add_watch(node, key, watch->token); > + > + watch->node = g_strdup(node); > + watch->key = g_strdup(key); > + watch->handler = handler; > + watch->opaque = opaque; > + watch->notifier.notify = watch_notify; > + > + 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); > + > + g_free(watch->token); > + g_free(watch->key); > + g_free(watch->node); > + > + g_free(watch); It would be better to have a function that will free/dispose of a XenWatch, or maybe simply calling xen_bus_remove_watch here might be enough. > + watch = NULL; You could return NULL instead. > + } > + > + return watch; > +} > + > +static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch) > +{ > + trace_xen_bus_remove_watch(watch->node, watch->key, watch->token); > + > + xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token); > + > + notifier_remove(&watch->notifier); > + > + g_free(watch->token); > + g_free(watch->key); > + g_free(watch->node); > + > + g_free(watch); > +} > +static void xen_bus_watch(void *opaque) > +{ > + XenBus *xenbus = opaque; > + char **v; > + const char *token; > + unsigned int n; > + > + g_assert(xenbus->xsh); > + > + v = xs_read_watch(xenbus->xsh, &n); What is the n for? Also, maybe you wanted to call xs_check_watch instead? (In a loop, until EGAIN) > + 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); > @@ -230,12 +419,24 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp) > error_propagate(errp, local_err); > error_prepend(errp, "failed to create frontend: "); > } > + > + xendev->frontend_state_watch = > + xen_bus_add_watch(xenbus, xendev->frontend_path, "state", > + xen_device_frontend_changed, xendev, &local_err); You can't reuse local_err here, *local_err must be null (It isn't exactly written like this, but that what I understand from reading qapi/error.h). Maybe you meant to return when the previous function failed (call of xs_node_create)? > + if (local_err) { > + error_propagate(errp, local_err); > + error_prepend(errp, "failed to watch frontend state: "); > + } > } Thanks,
> -----Original Message----- > From: Anthony PERARD [mailto:anthony.perard@citrix.com] > Sent: 03 December 2018 14:43 > To: Paul Durrant <Paul.Durrant@citrix.com> > Cc: qemu-block@nongnu.org; qemu-devel@nongnu.org; xen- > devel@lists.xenproject.org; Kevin Wolf <kwolf@redhat.com>; Max Reitz > <mreitz@redhat.com>; Stefano Stabellini <sstabellini@kernel.org> > Subject: Re: [PATCH 05/18] xen: add xenstore watcher infratructure > > On Wed, Nov 21, 2018 at 03:11:58PM +0000, Paul Durrant wrote: > > 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-qisk implementation is extended with a 'frontend_changed' > method, > > "The xen-qdisk" It's xen-block now :-) > > > 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> > > --- > > diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c > > index 0859643f7d..35f7b70480 100644 > > --- a/hw/block/xen-qdisk.c > > +++ b/hw/block/xen-qdisk.c > > +static void xen_qdisk_frontend_changed(XenDevice *xendev, > > + enum xenbus_state > frontend_state, > > + Error **errp) > > +{ > > + XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev); > > + 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_qdisk_disconnect(qdiskdev, &error_fatal); > > Do we want to crash (actually exit) QEMU when disconnect failed? > Ok, I'll propagate. > > + xen_qdisk_connect(qdiskdev, &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_qdisk_disconnect(qdiskdev, &error_fatal); > > + xen_device_backend_set_state(xendev, XenbusStateClosed); > > + break; > > + > > + default: > > + break; > > + } > > +} > > + > > diff --git a/hw/xen/xen-bus-helper.c b/hw/xen/xen-bus-helper.c > > index d9ee2ed6a0..b44acc8047 100644 > > --- a/hw/xen/xen-bus-helper.c > > +++ b/hw/xen/xen-bus-helper.c > > @@ -122,3 +122,31 @@ 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); > > + > > + if (!xs_watch(xsh, path, token)) { > > + error_setg_errno(errp, errno, "failed to watch path '%s'", > path); > > + } > > + > > + g_free(path); > > +} > > + > > +void xs_node_unwatch(struct xs_handle *xsh, const char *node, > > + const char *key, const char *token) > > +{ > > + char *path; > > + > > + path = (strlen(node) != 0) ? g_strdup_printf("%s/%s", node, key) : > > + g_strdup(key); > > + > > + xs_unwatch(xsh, path, token); > > I think we should check for error from xs_unwatch as well. Yes. > > > + > > + g_free(path); > > +} > > diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c > > index 663aa8e117..99988f8568 100644 > > --- a/hw/xen/xen-bus.c > > +++ b/hw/xen/xen-bus.c > > +static XenWatch *xen_bus_add_watch(XenBus *xenbus, const char *node, > > + const char *key, XenWatchHandler > handler, > > + void *opaque, Error **errp) > > +{ > > + XenWatch *watch = g_new0(XenWatch, 1); > > + QemuUUID uuid; > > + Error *local_err = NULL; > > + > > + qemu_uuid_generate(&uuid); > > + watch->token = qemu_uuid_unparse_strdup(&uuid); > > + > > + trace_xen_bus_add_watch(node, key, watch->token); > > + > > + watch->node = g_strdup(node); > > + watch->key = g_strdup(key); > > + watch->handler = handler; > > + watch->opaque = opaque; > > + watch->notifier.notify = watch_notify; > > + > > + 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); > > + > > + g_free(watch->token); > > + g_free(watch->key); > > + g_free(watch->node); > > + > > + g_free(watch); > > It would be better to have a function that will free/dispose of a > XenWatch, or maybe simply calling xen_bus_remove_watch here might be > enough. True. Too much cut'n'paste. > > > + watch = NULL; > > You could return NULL instead. > > > + } > > + > > + return watch; > > +} > > + > > +static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch) > > +{ > > + trace_xen_bus_remove_watch(watch->node, watch->key, watch->token); > > + > > + xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch- > >token); > > + > > + notifier_remove(&watch->notifier); > > + > > + g_free(watch->token); > > + g_free(watch->key); > > + g_free(watch->node); > > + > > + g_free(watch); > > +} > > > +static void xen_bus_watch(void *opaque) > > +{ > > + XenBus *xenbus = opaque; > > + char **v; > > + const char *token; > > + unsigned int n; > > + > > + g_assert(xenbus->xsh); > > + > > + v = xs_read_watch(xenbus->xsh, &n); > > What is the n for? > Also, maybe you wanted to call xs_check_watch instead? (In a loop, until > EGAIN) I don't need the loop. The 'n' is the length of the vector but xs_check_watch() does what I need. > > > + 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); > > @@ -230,12 +419,24 @@ static void xen_device_frontend_create(XenDevice > *xendev, Error **errp) > > error_propagate(errp, local_err); > > error_prepend(errp, "failed to create frontend: "); > > } > > + > > + xendev->frontend_state_watch = > > + xen_bus_add_watch(xenbus, xendev->frontend_path, "state", > > + xen_device_frontend_changed, xendev, > &local_err); > > You can't reuse local_err here, *local_err must be null (It isn't > exactly written like this, but that what I understand from reading > qapi/error.h). Oh, the code should have bailed on the first error. Paul > > Maybe you meant to return when the previous function failed (call of > xs_node_create)? > > > + if (local_err) { > > + error_propagate(errp, local_err); > > + error_prepend(errp, "failed to watch frontend state: "); > > + } > > } > > Thanks, > > -- > Anthony PERARD
diff --git a/hw/block/trace-events b/hw/block/trace-events index fd3c126ac1..8b95567560 100644 --- a/hw/block/trace-events +++ b/hw/block/trace-events @@ -130,4 +130,6 @@ xen_disk_free(char *name) "%s" # hw/block/xen-qdisk.c xen_qdisk_realize(uint32_t disk, uint32_t partition) "d%up%u" +xen_qdisk_connect(uint32_t disk, uint32_t partition) "d%up%u" +xen_qdisk_disconnect(uint32_t disk, uint32_t partition) "d%up%u" xen_qdisk_unrealize(uint32_t disk, uint32_t partition) "d%up%u" diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c index 0859643f7d..35f7b70480 100644 --- a/hw/block/xen-qdisk.c +++ b/hw/block/xen-qdisk.c @@ -32,12 +32,67 @@ static void xen_qdisk_realize(XenDevice *xendev, Error **errp) trace_xen_qdisk_realize(vdev->disk, vdev->partition); } +static void xen_qdisk_connect(XenQdiskDevice *qdiskdev, Error **errp) +{ + XenQdiskVdev *vdev = &qdiskdev->vdev; + + trace_xen_qdisk_connect(vdev->disk, vdev->partition); +} + +static void xen_qdisk_disconnect(XenQdiskDevice *qdiskdev, Error **errp) +{ + XenQdiskVdev *vdev = &qdiskdev->vdev; + + trace_xen_qdisk_disconnect(vdev->disk, vdev->partition); +} + +static void xen_qdisk_frontend_changed(XenDevice *xendev, + enum xenbus_state frontend_state, + Error **errp) +{ + XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev); + 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_qdisk_disconnect(qdiskdev, &error_fatal); + xen_qdisk_connect(qdiskdev, &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_qdisk_disconnect(qdiskdev, &error_fatal); + xen_device_backend_set_state(xendev, XenbusStateClosed); + break; + + default: + break; + } +} + static void xen_qdisk_unrealize(XenDevice *xendev, Error **errp) { XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev); XenQdiskVdev *vdev = &qdiskdev->vdev; trace_xen_qdisk_unrealize(vdev->disk, vdev->partition); + + xen_qdisk_disconnect(qdiskdev, &error_fatal); } static char *disk_to_vbd_name(unsigned int disk) @@ -246,6 +301,7 @@ static void xen_qdisk_class_init(ObjectClass *class, void *data) xendev_class->device = "vbd"; xendev_class->get_name = xen_qdisk_get_name; xendev_class->realize = xen_qdisk_realize; + xendev_class->frontend_changed = xen_qdisk_frontend_changed; xendev_class->unrealize = xen_qdisk_unrealize; dev_class->desc = "Xen Qdisk Device"; diff --git a/hw/xen/trace-events b/hw/xen/trace-events index fa8aea1da1..94c46c2e34 100644 --- a/hw/xen/trace-events +++ b/hw/xen/trace-events @@ -16,7 +16,11 @@ 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" diff --git a/hw/xen/xen-bus-helper.c b/hw/xen/xen-bus-helper.c index d9ee2ed6a0..b44acc8047 100644 --- a/hw/xen/xen-bus-helper.c +++ b/hw/xen/xen-bus-helper.c @@ -122,3 +122,31 @@ 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); + + if (!xs_watch(xsh, path, token)) { + error_setg_errno(errp, errno, "failed to watch path '%s'", path); + } + + g_free(path); +} + +void xs_node_unwatch(struct xs_handle *xsh, const char *node, + const char *key, const char *token) +{ + char *path; + + path = (strlen(node) != 0) ? g_strdup_printf("%s/%s", node, key) : + g_strdup(key); + + xs_unwatch(xsh, path, token); + + g_free(path); +} diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 663aa8e117..99988f8568 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -4,6 +4,9 @@ */ #include "qemu/osdep.h" +#include "qemu/error-report.h" +#include "qemu/main-loop.h" +#include "qemu/uuid.h" #include "hw/hw.h" #include "hw/sysbus.h" #include "hw/xen/xen.h" @@ -57,6 +60,78 @@ 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 *xen_bus_add_watch(XenBus *xenbus, const char *node, + const char *key, XenWatchHandler handler, + void *opaque, Error **errp) +{ + XenWatch *watch = g_new0(XenWatch, 1); + QemuUUID uuid; + Error *local_err = NULL; + + qemu_uuid_generate(&uuid); + watch->token = qemu_uuid_unparse_strdup(&uuid); + + trace_xen_bus_add_watch(node, key, watch->token); + + watch->node = g_strdup(node); + watch->key = g_strdup(key); + watch->handler = handler; + watch->opaque = opaque; + watch->notifier.notify = watch_notify; + + 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); + + g_free(watch->token); + g_free(watch->key); + g_free(watch->node); + + g_free(watch); + watch = NULL; + } + + return watch; +} + +static void xen_bus_remove_watch(XenBus *xenbus, XenWatch *watch) +{ + trace_xen_bus_remove_watch(watch->node, watch->key, watch->token); + + xs_node_unwatch(xenbus->xsh, watch->node, watch->key, watch->token); + + notifier_remove(&watch->notifier); + + g_free(watch->token); + g_free(watch->key); + g_free(watch->node); + + g_free(watch); +} + static void xen_bus_unrealize(BusState *bus, Error **errp) { XenBus *xenbus = XEN_BUS(bus); @@ -67,9 +142,34 @@ 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; + unsigned int n; + + g_assert(xenbus->xsh); + + v = xs_read_watch(xenbus->xsh, &n); + 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); @@ -90,6 +190,9 @@ 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: @@ -127,8 +230,25 @@ static void xen_device_backend_printf(XenDevice *xendev, const char *key, va_end(ap); } -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, 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)); @@ -143,6 +263,11 @@ 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))); @@ -193,6 +318,23 @@ static void xen_device_frontend_printf(XenDevice *xendev, const char *key, va_end(ap); } +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, fmt, + ap); + va_end(ap); + + return rc; +} + static void xen_device_frontend_set_state(XenDevice *xendev, enum xenbus_state state) { @@ -209,6 +351,53 @@ 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) { + const char *msg = error_get_pretty(local_err); + + error_report("frontend change error: %s", msg); + error_free(local_err); + } + } + + /* + * 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))); @@ -230,12 +419,24 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp) error_propagate(errp, local_err); error_prepend(errp, "failed to create frontend: "); } + + 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(errp, local_err); + error_prepend(errp, "failed to watch frontend state: "); + } } static void xen_device_frontend_destroy(XenDevice *xendev) { XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev))); + if (xendev->frontend_state_watch) { + xen_bus_remove_watch(xenbus, xendev->frontend_state_watch); + } + if (!xendev->frontend_path) { return; } diff --git a/include/hw/xen/xen-bus-helper.h b/include/hw/xen/xen-bus-helper.h index 53570650db..3b88efaa0c 100644 --- a/include/hw/xen/xen-bus-helper.h +++ b/include/hw/xen/xen-bus-helper.h @@ -23,4 +23,9 @@ 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, const char *fmt, ...); +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); + #endif /* HW_XEN_BUS_HELPER_H */ diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h index 434d1dbf58..954149e51b 100644 --- a/include/hw/xen/xen-bus.h +++ b/include/hw/xen/xen-bus.h @@ -8,6 +8,11 @@ #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; @@ -16,10 +21,14 @@ 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 { @@ -30,6 +39,7 @@ typedef struct XenDeviceClass { const char *device; XenDeviceGetName get_name; XenDeviceRealize realize; + XenDeviceFrontendChanged frontend_changed; XenDeviceUnrealize unrealize; } XenDeviceClass; @@ -45,6 +55,7 @@ typedef struct XenBus { BusState qbus; domid_t backend_id; struct xs_handle *xsh; + NotifierList watch_notifiers; } XenBus; typedef struct XenBusClass { @@ -62,4 +73,8 @@ 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 */
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-qisk 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> --- Cc: Kevin Wolf <kwolf@redhat.com> Cc: Max Reitz <mreitz@redhat.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Anthony Perard <anthony.perard@citrix.com> --- hw/block/trace-events | 2 + hw/block/xen-qdisk.c | 56 +++++++++++ hw/xen/trace-events | 4 + hw/xen/xen-bus-helper.c | 28 ++++++ hw/xen/xen-bus.c | 205 +++++++++++++++++++++++++++++++++++++++- include/hw/xen/xen-bus-helper.h | 5 + include/hw/xen/xen-bus.h | 15 +++ 7 files changed, 313 insertions(+), 2 deletions(-)