Subject: [PATCH v3 13/15] powerpc/64s: machine check do not trace real-mode handler

From: Nicholas Piggin <[email-masked]>
Date: Tue, 7 Apr 2020 15:16:34 +1000

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.

Acked-by: Naveen N. Rao <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kernel/mce.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index be7e3f92a7b5..fd90c0eda229 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -16,6 +16,7 @@
 #include <linux/export.h>
 #include <linux/irq_work.h>
 #include <linux/extable.h>
+#include <linux/ftrace.h>
 
 #include <asm/machdep.h>
 #include <asm/mce.h>
@@ -571,10 +572,14 @@ EXPORT_SYMBOL_GPL(machine_check_print_event_info);
  *
  * 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;
 	bool nested = in_nmi();
+	u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
+
+	this_cpu_set_ftrace_enabled(0);
+
 	if (!nested)
 		nmi_enter();
 
@@ -589,6 +594,8 @@ long machine_check_early(struct pt_regs *regs)
 	if (!nested)
 		nmi_exit();
 
+	this_cpu_set_ftrace_enabled(ftrace_enabled);
+
 	return handled;
 }
 
-- 
2.23.0