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authorBoris Ostrovsky <boris.ostrovsky@oracle.com>2019-09-30 16:44:41 -0400
committerBoris Ostrovsky <boris.ostrovsky@oracle.com>2019-10-07 17:53:30 -0400
commitc6875f3aacf2a5a913205accddabf0bfb75cac76 (patch)
treeab2ad24560746f3b179b5c3d48ee8461a1eee0d9
parenta8fabb38525c51a094607768bac3ba46b3f4a9d5 (diff)
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>
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt4
-rw-r--r--arch/x86/xen/enlighten.c28
2 files changed, 29 insertions, 3 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4c1971960afa..5ea005c9e2d6 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.
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 750f46ad018a..205b1176084f 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -269,19 +269,41 @@ 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

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