Commit c6875f3a authored by Boris Ostrovsky's avatar Boris Ostrovsky

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: default avatarJames Dingwall <james@dingwall.me.uk>
Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
parent a8fabb38
...@@ -5267,6 +5267,10 @@ ...@@ -5267,6 +5267,10 @@
the unplug protocol the unplug protocol
never -- do not unplug even if version check succeeds 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] xen_nopvspin [X86,XEN]
Disables the ticketlock slowpath using Xen PV Disables the ticketlock slowpath using Xen PV
optimizations. optimizations.
......
...@@ -269,19 +269,41 @@ void xen_reboot(int reason) ...@@ -269,19 +269,41 @@ void xen_reboot(int reason)
BUG(); BUG();
} }
static int reboot_reason = SHUTDOWN_reboot;
static bool xen_legacy_crash;
void xen_emergency_restart(void) void xen_emergency_restart(void)
{ {
xen_reboot(SHUTDOWN_reboot); xen_reboot(reboot_reason);
} }
static int static int
xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr) xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
{ {
if (!kexec_crash_loaded()) if (!kexec_crash_loaded()) {
xen_reboot(SHUTDOWN_crash); 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; 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 = { static struct notifier_block xen_panic_block = {
.notifier_call = xen_panic_event, .notifier_call = xen_panic_event,
.priority = INT_MIN .priority = INT_MIN
......
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