After triggering a crash dump in a HVM guest, the PV backend drivers
will remain in connected state. When the kdump kernel starts the PV
drivers will skip such devices. As a result, no root device is found
and the vmcore cant be saved.
With this change all frontend devices with state XenbusStateConnected
will be reset by changing the state file to Closing/Closed/Initializing.
This will trigger a disconnect in the backend drivers. Now the frontend
drivers will find the backend drivers in state Initwait and can connect.
Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
v2:
add missing newlines to new printk() output
drivers/xen/xenbus/xenbus_comms.c | 4 +
drivers/xen/xenbus/xenbus_probe.c | 96 ++++++++++++++++++++++++++++++++++++++
2 files changed, 99 insertions(+), 1 deletion(-)
Index: linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_comms.c
===================================================================
--- linux-2.6.18-xen.hg.orig/drivers/xen/xenbus/xenbus_comms.c
+++ linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_comms.c
@@ -234,7 +234,9 @@ int xb_init_comms(void)
printk(KERN_WARNING "XENBUS response ring is not quiescent "
"(%08x:%08x): fixing up\n",
intf->rsp_cons, intf->rsp_prod);
- intf->rsp_cons = intf->rsp_prod;
+ /* breaks kdump */
+ if (!reset_devices)
+ intf->rsp_cons = intf->rsp_prod;
}
if (xenbus_irq)
Index: linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_probe.c
===================================================================
--- linux-2.6.18-xen.hg.orig/drivers/xen/xenbus/xenbus_probe.c
+++ linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_probe.c
@@ -854,11 +854,107 @@ void unregister_xenstore_notifier(struct
}
EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
+#ifdef CONFIG_CRASH_DUMP
+static DECLARE_WAIT_QUEUE_HEAD(be_state_wq);
+static int be_state;
+
+static void xenbus_reset_state_changed(struct xenbus_watch *w, const char **v,
unsigned int l)
+{
+ xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &be_state);
+ printk(KERN_INFO "XENBUS: %s %s\n", v[XS_WATCH_PATH],
xenbus_strstate(be_state));
+ wake_up(&be_state_wq);
+}
+
+static int xenbus_reset_check_final(int *st)
+{
+ return *st == XenbusStateInitialising || *st == XenbusStateInitWait;
+}
+
+static void xenbus_reset_frontend_state(char *backend, char *frontend)
+{
+ struct xenbus_watch watch;
+
+ memset(&watch, 0, sizeof(watch));
+ watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", backend);
+ if (!watch.node)
+ return;
+
+ watch.callback = xenbus_reset_state_changed;
+ be_state = XenbusStateUnknown;
+
+ printk(KERN_INFO "triggering reconnect on %s\n", backend);
+ register_xenbus_watch(&watch);
+
+ xenbus_printf(XBT_NIL, frontend, "state", "%d", XenbusStateClosing);
+ wait_event_interruptible(be_state_wq, be_state == XenbusStateClosing);
+
+ xenbus_printf(XBT_NIL, frontend, "state", "%d", XenbusStateClosed);
+ wait_event_interruptible(be_state_wq, be_state == XenbusStateClosed);
+
+ xenbus_printf(XBT_NIL, frontend, "state", "%d",
XenbusStateInitialising);
+ wait_event_interruptible(be_state_wq,
xenbus_reset_check_final(&be_state));
+
+ unregister_xenbus_watch(&watch);
+ printk(KERN_INFO "reconnect done on %s\n", backend);
+ kfree(watch.node);
+}
+
+static void xenbus_reset_check_state(char *frontend)
+{
+ int state, err;
+ char *backend;
+
+ err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &state);
+ /* frontend connected? */
+ if (err == 1 && state == XenbusStateConnected) {
+ backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
+ if (!backend || IS_ERR(backend))
+ return;
+ err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &state);
+ /* backend connected? */
+ if (err == 1 && state == XenbusStateConnected)
+ xenbus_reset_frontend_state(backend, frontend);
+ kfree(backend);
+ }
+}
+
+static void xenbus_reset_state(void)
+{
+ char *frontend;
+ char **devclass, **dev;
+ int devclass_n, dev_n;
+ int i, j;
+
+ devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
+ if (IS_ERR(devclass))
+ return;
+
+ for (i = 0; i < devclass_n; i++) {
+ dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
+ if (IS_ERR(dev))
+ continue;
+ for (j = 0; j < dev_n; j++) {
+ frontend = kasprintf(GFP_NOIO|__GFP_HIGH,
"device/%s/%s", devclass[i], dev[j]);
+ if (!frontend)
+ continue;
+ xenbus_reset_check_state(frontend);
+ kfree(frontend);
+ }
+ kfree(dev);
+ }
+ kfree(devclass);
+}
+#endif
void xenbus_probe(void *unused)
{
BUG_ON(!is_xenstored_ready());
+#ifdef CONFIG_CRASH_DUMP
+ /* reset devices in XenbusStateConnected state */
+ if (!is_initial_xendomain() && reset_devices)
+ xenbus_reset_state();
+#endif
/* Enumerate devices in xenstore and watch for changes. */
xenbus_probe_devices(&xenbus_frontend);
register_xenbus_watch(&fe_watch);
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