hw/xen: Add emulated implementation of XenStore operations
Now that we have an internal implementation of XenStore, we can populate the xenstore_backend_ops to allow PV backends to talk to it. Watches can't be processed with immediate callbacks because that would call back into XenBus code recursively. Defer them to a QEMUBH to be run as appropriate from the main loop. We use a QEMUBH per XS handle, and it walks all the watches (there shouldn't be many per handle) to fire any which have pending events. We *could* have done it differently but this allows us to use the same struct watch_event as we have for the guest side, and keeps things relatively simple. Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse
parent
b08d88e30f
commit
0324751272
@ -49,7 +49,7 @@ struct XenXenstoreState {
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/*< public >*/
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XenstoreImplState *impl;
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GList *watch_events;
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GList *watch_events; /* for the guest */
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MemoryRegion xenstore_page;
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struct xenstore_domain_interface *xs;
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@ -73,6 +73,8 @@ struct XenXenstoreState *xen_xenstore_singleton;
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static void xen_xenstore_event(void *opaque);
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static void fire_watch_cb(void *opaque, const char *path, const char *token);
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static struct xenstore_backend_ops emu_xenstore_backend_ops;
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static void G_GNUC_PRINTF (4, 5) relpath_printf(XenXenstoreState *s,
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GList *perms,
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const char *relpath,
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@ -169,6 +171,8 @@ static void xen_xenstore_realize(DeviceState *dev, Error **errp)
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relpath_printf(s, perms, "feature", "%s", "");
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g_list_free_full(perms, g_free);
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xen_xenstore_ops = &emu_xenstore_backend_ops;
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}
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static bool xen_xenstore_is_needed(void *opaque)
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@ -1306,6 +1310,15 @@ struct watch_event {
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char *token;
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};
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static void free_watch_event(struct watch_event *ev)
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{
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if (ev) {
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g_free(ev->path);
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g_free(ev->token);
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g_free(ev);
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}
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}
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static void queue_watch(XenXenstoreState *s, const char *path,
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const char *token)
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{
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@ -1352,9 +1365,7 @@ static void process_watch_events(XenXenstoreState *s)
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deliver_watch(s, ev->path, ev->token);
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s->watch_events = g_list_remove(s->watch_events, ev);
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g_free(ev->path);
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g_free(ev->token);
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g_free(ev);
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free_watch_event(ev);
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}
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static void xen_xenstore_event(void *opaque)
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@ -1444,3 +1455,257 @@ int xen_xenstore_reset(void)
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return 0;
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}
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struct qemu_xs_handle {
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XenstoreImplState *impl;
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GList *watches;
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QEMUBH *watch_bh;
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};
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struct qemu_xs_watch {
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struct qemu_xs_handle *h;
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char *path;
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xs_watch_fn fn;
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void *opaque;
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GList *events;
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};
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static char *xs_be_get_domain_path(struct qemu_xs_handle *h, unsigned int domid)
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{
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return g_strdup_printf("/local/domain/%u", domid);
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}
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static char **xs_be_directory(struct qemu_xs_handle *h, xs_transaction_t t,
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const char *path, unsigned int *num)
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{
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GList *items = NULL, *l;
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unsigned int i = 0;
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char **items_ret;
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int err;
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err = xs_impl_directory(h->impl, DOMID_QEMU, t, path, NULL, &items);
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if (err) {
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errno = err;
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return NULL;
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}
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items_ret = g_new0(char *, g_list_length(items) + 1);
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*num = 0;
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for (l = items; l; l = l->next) {
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items_ret[i++] = l->data;
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(*num)++;
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}
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g_list_free(items);
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return items_ret;
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}
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static void *xs_be_read(struct qemu_xs_handle *h, xs_transaction_t t,
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const char *path, unsigned int *len)
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{
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GByteArray *data = g_byte_array_new();
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bool free_segment = false;
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int err;
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err = xs_impl_read(h->impl, DOMID_QEMU, t, path, data);
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if (err) {
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free_segment = true;
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errno = err;
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} else {
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if (len) {
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*len = data->len;
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}
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/* The xen-bus-helper code expects to get NUL terminated string! */
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g_byte_array_append(data, (void *)"", 1);
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}
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return g_byte_array_free(data, free_segment);
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}
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static bool xs_be_write(struct qemu_xs_handle *h, xs_transaction_t t,
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const char *path, const void *data, unsigned int len)
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{
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GByteArray *gdata = g_byte_array_new();
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int err;
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g_byte_array_append(gdata, data, len);
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err = xs_impl_write(h->impl, DOMID_QEMU, t, path, gdata);
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g_byte_array_unref(gdata);
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if (err) {
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errno = err;
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return false;
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}
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return true;
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}
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static bool xs_be_create(struct qemu_xs_handle *h, xs_transaction_t t,
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unsigned int owner, unsigned int domid,
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unsigned int perms, const char *path)
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{
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g_autoptr(GByteArray) data = g_byte_array_new();
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GList *perms_list = NULL;
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int err;
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/* mkdir does this */
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err = xs_impl_read(h->impl, DOMID_QEMU, t, path, data);
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if (err == ENOENT) {
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err = xs_impl_write(h->impl, DOMID_QEMU, t, path, data);
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}
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if (err) {
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errno = err;
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return false;
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}
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perms_list = g_list_append(perms_list,
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xs_perm_as_string(XS_PERM_NONE, owner));
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perms_list = g_list_append(perms_list,
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xs_perm_as_string(perms, domid));
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err = xs_impl_set_perms(h->impl, DOMID_QEMU, t, path, perms_list);
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g_list_free_full(perms_list, g_free);
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if (err) {
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errno = err;
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return false;
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}
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return true;
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}
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static bool xs_be_destroy(struct qemu_xs_handle *h, xs_transaction_t t,
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const char *path)
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{
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int err = xs_impl_rm(h->impl, DOMID_QEMU, t, path);
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if (err) {
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errno = err;
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return false;
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}
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return true;
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}
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static void be_watch_bh(void *_h)
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{
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struct qemu_xs_handle *h = _h;
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GList *l;
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for (l = h->watches; l; l = l->next) {
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struct qemu_xs_watch *w = l->data;
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while (w->events) {
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struct watch_event *ev = w->events->data;
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w->fn(w->opaque, ev->path);
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w->events = g_list_remove(w->events, ev);
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free_watch_event(ev);
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}
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}
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}
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static void xs_be_watch_cb(void *opaque, const char *path, const char *token)
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{
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struct watch_event *ev = g_new0(struct watch_event, 1);
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struct qemu_xs_watch *w = opaque;
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/* We don't care about the token */
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ev->path = g_strdup(path);
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w->events = g_list_append(w->events, ev);
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qemu_bh_schedule(w->h->watch_bh);
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}
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static struct qemu_xs_watch *xs_be_watch(struct qemu_xs_handle *h,
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const char *path, xs_watch_fn fn,
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void *opaque)
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{
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struct qemu_xs_watch *w = g_new0(struct qemu_xs_watch, 1);
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int err;
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w->h = h;
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w->fn = fn;
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w->opaque = opaque;
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err = xs_impl_watch(h->impl, DOMID_QEMU, path, NULL, xs_be_watch_cb, w);
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if (err) {
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errno = err;
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g_free(w);
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return NULL;
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}
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w->path = g_strdup(path);
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h->watches = g_list_append(h->watches, w);
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return w;
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}
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static void xs_be_unwatch(struct qemu_xs_handle *h, struct qemu_xs_watch *w)
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{
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xs_impl_unwatch(h->impl, DOMID_QEMU, w->path, NULL, xs_be_watch_cb, w);
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h->watches = g_list_remove(h->watches, w);
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g_list_free_full(w->events, (GDestroyNotify)free_watch_event);
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g_free(w->path);
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g_free(w);
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}
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static xs_transaction_t xs_be_transaction_start(struct qemu_xs_handle *h)
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{
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unsigned int new_tx = XBT_NULL;
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int err = xs_impl_transaction_start(h->impl, DOMID_QEMU, &new_tx);
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if (err) {
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errno = err;
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return XBT_NULL;
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}
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return new_tx;
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}
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static bool xs_be_transaction_end(struct qemu_xs_handle *h, xs_transaction_t t,
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bool abort)
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{
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int err = xs_impl_transaction_end(h->impl, DOMID_QEMU, t, !abort);
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if (err) {
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errno = err;
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return false;
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}
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return true;
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}
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static struct qemu_xs_handle *xs_be_open(void)
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{
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XenXenstoreState *s = xen_xenstore_singleton;
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struct qemu_xs_handle *h;
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if (!s && !s->impl) {
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errno = -ENOSYS;
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return NULL;
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}
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h = g_new0(struct qemu_xs_handle, 1);
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h->impl = s->impl;
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h->watch_bh = aio_bh_new(qemu_get_aio_context(), be_watch_bh, h);
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return h;
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}
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static void xs_be_close(struct qemu_xs_handle *h)
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{
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while (h->watches) {
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struct qemu_xs_watch *w = h->watches->data;
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xs_be_unwatch(h, w);
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}
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qemu_bh_delete(h->watch_bh);
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g_free(h);
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}
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static struct xenstore_backend_ops emu_xenstore_backend_ops = {
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.open = xs_be_open,
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.close = xs_be_close,
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.get_domain_path = xs_be_get_domain_path,
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.directory = xs_be_directory,
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.read = xs_be_read,
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.write = xs_be_write,
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.create = xs_be_create,
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.destroy = xs_be_destroy,
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.watch = xs_be_watch,
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.unwatch = xs_be_unwatch,
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.transaction_start = xs_be_transaction_start,
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.transaction_end = xs_be_transaction_end,
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};
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