misc: pvpanic: add crash loaded event

Some users prefer kdump tools to generate guest kernel dumpfile,
at the same time, need a out-of-band kernel panic event.

Currently if booting guest kernel with 'crash_kexec_post_notifiers',
QEMU will receive PVPANIC_PANICKED event and stop VM. If booting
guest kernel without 'crash_kexec_post_notifiers', guest will not
call notifier chain.

Add PVPANIC_CRASH_LOADED bit for pvpanic event, it means that guest
kernel actually hit a kernel panic, but the guest kernel wants to
handle by itself.
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Link: https://lore.kernel.org/r/20200102023513.318836-3-pizhenwei@bytedance.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/pvpanic.c

@@ -10,6 +10,7 @@
 
 #include <linux/acpi.h>
 #include <linux/kernel.h>
+#include <linux/kexec.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
@@ -33,7 +34,13 @@ static int
 pvpanic_panic_notify(struct notifier_block *nb, unsigned long code,
 		     void *unused)
 {
-	pvpanic_send_event(PVPANIC_PANICKED);
+	unsigned int event = PVPANIC_PANICKED;
+
+	if (kexec_crash_loaded())
+		event = PVPANIC_CRASH_LOADED;
+
+	pvpanic_send_event(event);
+
 	return NOTIFY_DONE;
 }
 

include/uapi/misc/pvpanic.h

@@ -4,5 +4,6 @@
 #define __PVPANIC_H__
 
 #define PVPANIC_PANICKED	(1 << 0)
+#define PVPANIC_CRASH_LOADED	(1 << 1)
 
 #endif /* __PVPANIC_H__ */