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authorPaul Durrant <pdurrant@amazon.com>2020-10-01 09:15:00 +0100
committerAnthony PERARD <anthony.perard@citrix.com>2020-10-19 16:32:41 +0100
commitc4583c8c394ee49ce7d5271f572abd3b000fa9e4 (patch)
tree98fbb64c939b023f063abe2c2ff86c0db662904f /hw/xen/xen-bus.c
parent2211118a2acb6f36bc497713479050e45a3ec693 (diff)
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>
Diffstat (limited to 'hw/xen/xen-bus.c')
-rw-r--r--hw/xen/xen-bus.c40
1 files changed, 32 insertions, 8 deletions
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index 9ce1c9540b..8c588920d9 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -430,7 +430,15 @@ static void xen_bus_unrealize(BusState *bus)
trace_xen_bus_unrealize();
if (xenbus->backend_watch) {
- xen_bus_remove_watch(xenbus, xenbus->backend_watch, NULL);
+ unsigned int i;
+
+ for (i = 0; i < xenbus->backend_types; i++) {
+ if (xenbus->backend_watch[i]) {
+ xen_bus_remove_watch(xenbus, xenbus->backend_watch[i], NULL);
+ }
+ }
+
+ g_free(xenbus->backend_watch);
xenbus->backend_watch = NULL;
}
@@ -446,8 +454,11 @@ static void xen_bus_unrealize(BusState *bus)
static void xen_bus_realize(BusState *bus, Error **errp)
{
+ char *key = g_strdup_printf("%u", xen_domid);
XenBus *xenbus = XEN_BUS(bus);
unsigned int domid;
+ const char **type;
+ unsigned int i;
Error *local_err = NULL;
trace_xen_bus_realize();
@@ -469,19 +480,32 @@ static void xen_bus_realize(BusState *bus, Error **errp)
module_call_init(MODULE_INIT_XEN_BACKEND);
- xenbus->backend_watch =
- xen_bus_add_watch(xenbus, "", /* domain root node */
- "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,
- "failed to set up enumeration watch: ");
+ type = xen_backend_get_types(&xenbus->backend_types);
+ xenbus->backend_watch = g_new(XenWatch *, xenbus->backend_types);
+
+ for (i = 0; i < xenbus->backend_types; i++) {
+ char *node = g_strdup_printf("backend/%s", type[i]);
+
+ xenbus->backend_watch[i] =
+ xen_bus_add_watch(xenbus, node, key, 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,
+ "failed to set up '%s' enumeration watch: ",
+ type[i]);
+ }
+
+ g_free(node);
}
+ g_free(type);
+ g_free(key);
return;
fail:
xen_bus_unrealize(bus);
+ g_free(key);
}
static void xen_bus_unplug_request(HotplugHandler *hotplug,