From abd106fb437ad1cd8c8df8ccabd0fa941ef6342a Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Fri, 8 May 2020 14:34:05 +1000
Subject: [PATCH] powerpc/64s: machine check do not trace real-mode handler

References: bsc#1094244 ltc#168122
Patch-mainline: v5.8-rc1
Git-commit: abd106fb437ad1cd8c8df8ccabd0fa941ef6342a

Rather than notrace annotations throughout a significant part of the
machine check code across kernel/ pseries/ and powernv/ which can
easily be broken and is infrequently tested, use paca->ftrace_enabled
to blanket-disable tracing of the real-mode non-maskable handler.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Link: https://lore.kernel.org/r/20200508043408.886394-14-npiggin@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kernel/mce.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -28,6 +28,7 @@
 #include <linux/percpu.h>
 #include <linux/export.h>
 #include <linux/irq_work.h>
+#include <linux/ftrace.h>
 
 #include <asm/machdep.h>
 #include <asm/mce.h>
@@ -456,9 +457,12 @@ EXPORT_SYMBOL(get_mce_fault_addr);
  *
  * regs->nip and regs->msr contains srr0 and ssr1.
  */
-long machine_check_early(struct pt_regs *regs)
+long notrace machine_check_early(struct pt_regs *regs)
 {
 	long handled = 0;
+	u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
+
+	this_cpu_set_ftrace_enabled(0);
 
 	hv_nmi_check_nonrecoverable(regs);
 
@@ -467,6 +471,9 @@ long machine_check_early(struct pt_regs
 	 */
 	if (ppc_md.machine_check_early)
 		handled = ppc_md.machine_check_early(regs);
+
+	this_cpu_set_ftrace_enabled(ftrace_enabled);
+
 	return handled;
 }