From 390869338382eea94cf43bb138867b420a6ec228 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Sat, 11 Sep 2021 12:13:56 +0800
Subject: [PATCH] Intel: hardirq/nmi: Allow nested nmi_enter()

mainline inclusion
from mainline-v5.8-rc1
commit 69ea03b56ed2c7189ccd0b5910ad39f3cad1df21
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I47H3V
CVE: NA

--------------------------------

commit 69ea03b56ed2c7189ccd0b5910ad39f3cad1df21 upstream
Backport summary: Backport to kernel 4.19.57 to enhance MCA-R for
copyin, backporting removes the changes to non-x86 architecture.

Since there are already a number of sites (ARM64, PowerPC) that effectively
nest nmi_enter(), make the primitive support this before adding even more.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lkml.kernel.org/r/20200505134100.864179229@linutronix.de
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 include/linux/hardirq.h | 5 ++++-
 include/linux/preempt.h | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index da0af631ded5..9c4ed2c4b45c 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -65,13 +65,16 @@ extern void irq_exit(void);
 #define arch_nmi_exit()		do { } while (0)
 #endif
 
+/*
+ * nmi_enter() can nest up to 15 times; see NMI_BITS.
+ */
 #define nmi_enter()						\
 	do {							\
 		arch_nmi_enter();				\
 		printk_nmi_enter();				\
 		lockdep_off();					\
 		ftrace_nmi_enter();				\
-		BUG_ON(in_nmi());				\
+		BUG_ON(in_nmi() == NMI_MASK);			\
 		preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET);	\
 		rcu_nmi_enter();				\
 		trace_hardirq_enter();				\
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index c01813c3fbe9..f10333a2b676 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -26,13 +26,13 @@
  *         PREEMPT_MASK:	0x000000ff
  *         SOFTIRQ_MASK:	0x0000ff00
  *         HARDIRQ_MASK:	0x000f0000
- *             NMI_MASK:	0x00100000
+ *             NMI_MASK:	0x00f00000
  * PREEMPT_NEED_RESCHED:	0x80000000
  */
 #define PREEMPT_BITS	8
 #define SOFTIRQ_BITS	8
 #define HARDIRQ_BITS	4
-#define NMI_BITS	1
+#define NMI_BITS	4
 
 #define PREEMPT_SHIFT	0
 #define SOFTIRQ_SHIFT	(PREEMPT_SHIFT + PREEMPT_BITS)
-- 
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