(this is actually a forward port of rev 1079 from 2.6.18.hg, untested because
kdump just hangs before (or while) entering the crash kernel in 3.0)
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>
---
drivers/xen/xenbus/xenbus_comms.c | 4 -
drivers/xen/xenbus/xenbus_probe_frontend.c | 97 +++++++++++++++++++++++++++++
2 files changed, 100 insertions(+), 1 deletion(-)
Index: linux-3.0/drivers/xen/xenbus/xenbus_comms.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_comms.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_comms.c
@@ -212,7 +212,9 @@ 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-3.0/drivers/xen/xenbus/xenbus_probe_frontend.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_probe_frontend.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_probe_frontend.c
@@ -254,10 +254,107 @@ int __xenbus_register_frontend(struct xe
}
EXPORT_SYMBOL_GPL(__xenbus_register_frontend);
+#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 "XENBUS: 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 "XENBUS: reconnect done on %s\n", backend);
+ kfree(watch.node);
+}
+
+static void xenbus_reset_check_state(char *class, char *dev)
+{
+ int state, err;
+ char *backend, *frontend;
+
+ frontend = kasprintf(GFP_NOIO | __GFP_HIGH, "device/%s/%s", class, dev);
+ if (!frontend)
+ return;
+
+ 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))
+ goto out;
+ err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &state);
+ /* backend connected? */
+ if (err == 1 && state == XenbusStateConnected)
+ xenbus_reset_frontend_state(backend, frontend);
+ kfree(backend);
+ }
+out:
+ kfree(frontend);
+}
+
+static void xenbus_reset_state(void)
+{
+ 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++)
+ xenbus_reset_check_state(devclass[i], dev[j]);
+ kfree(dev);
+ }
+ kfree(devclass);
+}
+#endif
+
static int frontend_probe_and_watch(struct notifier_block *notifier,
unsigned long event,
void *data)
{
+#ifdef CONFIG_CRASH_DUMP
+ /* reset devices in XenbusStateConnected state */
+ if (!xen_initial_domain() && 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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