From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
[ Upstream commit c6875f3aacf2a5a913205accddabf0bfb75cac76 ]
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@xxxxxxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 4 +++
arch/x86/xen/enlighten.c | 28 +++++++++++++++++--
2 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 188a7db8501bd..9d8b42afbe4f9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4873,6 +4873,10 @@
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.
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 515d5e4414c29..00fc683a20110 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -259,19 +259,41 @@ void xen_reboot(int reason)
BUG();
}
+static int reboot_reason = SHUTDOWN_reboot;
+static bool xen_legacy_crash;
void xen_emergency_restart(void)
{
- xen_reboot(SHUTDOWN_reboot);
+ xen_reboot(reboot_reason);
}
static int
xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
{
- if (!kexec_crash_loaded())
- xen_reboot(SHUTDOWN_crash);
+ if (!kexec_crash_loaded()) {
+ if (xen_legacy_crash)
+ xen_reboot(SHUTDOWN_crash);
+
+ reboot_reason = SHUTDOWN_crash;
+
+ /*
+ * If panic_timeout==0 then we are supposed to wait forever.
+ * However, to preserve original dom0 behavior we have to drop
+ * into hypervisor. (domU behavior is controlled by its
+ * config file)
+ */
+ if (panic_timeout == 0)
+ panic_timeout = -1;
+ }
return NOTIFY_DONE;
}
+static int __init parse_xen_legacy_crash(char *arg)
+{
+ xen_legacy_crash = true;
+ return 0;
+}
+early_param("xen_legacy_crash", parse_xen_legacy_crash);
+
static struct notifier_block xen_panic_block = {
.notifier_call = xen_panic_event,
.priority = INT_MIN
--
2.20.1
