powerpc/powernv: Flush console before platform error reboot

Unrecovered MCE and HMI errors are sent through a special restart OPAL
call to log the platform error. The downside is that they don't go
through normal Linux crash paths, so they don't give much information
to the Linux console.

Change this by providing a special crash function which does some of
the console flushing from the panic() path before calling firmware to
reboot.

The downside of this is a little more code to execute before reaching
the firmware reboot. However in practice, it's critical to get the
Linux console messages output in order to debug a problem. So this is
a desirable tradeoff.

Note on the implementation: It is difficult to plumb a custom reboot
handler into the panic path, because panic does a little bit too much
work. For example, it will try to delay with the timebase, but that
may be corrupted in some cases resulting in a hang without reaching
the platform reboot. Another problem is that panic can invoke the
crash dump code which is not what we want in the case of a hardware
platform error. Long-term the best solution will be to rework the
panic path so it can be suitable for this kind of panic, but for now
we just duplicate a bit of the code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 3 insertions, 19 deletions

diff --git a/arch/powerpc/platforms/powernv/opal-hmi.c b/arch/powerpc/platforms/powernv/opal-hmi.c
index 88f3c61eec95..d78fed728cdf 100644
--- a/arch/powerpc/platforms/powernv/opal-hmi.c
+++ b/arch/powerpc/platforms/powernv/opal-hmi.c
@@ -30,6 +30,8 @@
 #include <asm/cputable.h>
 #include <asm/machdep.h>
 
+#include "powernv.h"
+
 static int opal_hmi_handler_nb_init;
 struct OpalHmiEvtNode {
 	struct list_head list;
@@ -267,8 +269,6 @@ static void hmi_event_handler(struct work_struct *work)
 	spin_unlock_irqrestore(&opal_hmi_evt_lock, flags);
 
 	if (unrecoverable) {
-		int ret;
-
 		/* Pull all HMI events from OPAL before we panic. */
 		while (opal_get_msg(__pa(&msg), sizeof(msg)) == OPAL_SUCCESS) {
 			u32 type;
@@ -284,23 +284,7 @@ static void hmi_event_handler(struct work_struct *work)
 			print_hmi_event_info(hmi_evt);
 		}
 
-		/*
-		 * Unrecoverable HMI exception. We need to inform BMC/OCC
-		 * about this error so that it can collect relevant data
-		 * for error analysis before rebooting.
-		 */
-		ret = opal_cec_reboot2(OPAL_REBOOT_PLATFORM_ERROR,
-			"Unrecoverable HMI exception");
-		if (ret == OPAL_UNSUPPORTED) {
-			pr_emerg("Reboot type %d not supported\n",
-						OPAL_REBOOT_PLATFORM_ERROR);
-		}
-
-		/*
-		 * Fall through and panic if opal_cec_reboot2() returns
-		 * OPAL_UNSUPPORTED.
-		 */
-		panic("Unrecoverable HMI exception");
+		pnv_platform_error_reboot(NULL, "Unrecoverable HMI exception");
 	}
 }