x86/xen: Return from panic notifier
Currently execution of panic() continues until Xen's panic notifier
(xen_panic_event()) is called at which point we make a hypercall that
never returns.
This means that any notifier that is supposed to be called later as
well as significant part of panic() code (such as pstore writes from
kmsg_dump()) is never executed.
There is no reason for xen_panic_event() to be this last point in
execution since panic()'s emergency_restart() will call into
xen_emergency_restart() from where we can perform our hypercall.
Nevertheless, we will provide xen_legacy_crash boot option that will
preserve original behavior during crash. This option could be used,
for example, if running kernel dumper (which happens after panic
notifiers) is undesirable.
Reported-by: James Dingwall <james@dingwall.me.uk>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4c19719..5ea005c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5267,6 +5267,10 @@
the unplug protocol
never -- do not unplug even if version check succeeds
+ xen_legacy_crash [X86,XEN]
+ Crash from Xen panic notifier, without executing late
+ panic() code such as dumping handler.
+
xen_nopvspin [X86,XEN]
Disables the ticketlock slowpath using Xen PV
optimizations.
