linux-kernel - [tip: x86/entry] x86/entry: Make NMI use IDTENTRY

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Date:   Fri, 12 Jun 2020 19:50:08 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/entry] x86/entry: Make NMI use IDTENTRY_RAW

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     71ed49d8fb33023f242419a77ecb1141c029cac4
Gitweb:        https://git.kernel.org/tip/71ed49d8fb33023f242419a77ecb1141c029cac4
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 12 Jun 2020 14:02:27 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 12 Jun 2020 14:15:48 +02:00

x86/entry: Make NMI use IDTENTRY_RAW

For no reason other than beginning brainmelt, IDTENTRY_NMI was mapped to
IDTENTRY_IST.

This is not a problem on 64bit because the IST default entry point maps to
IDTENTRY_RAW which does not any entry handling. The surplus function
declaration for the noist C entry point is unused and as there is no ASM
code emitted for NMI this went unnoticed.

On 32bit IDTENTRY_IST maps to a regular IDTENTRY which does the normal
entry handling. That is clearly the wrong thing to do for NMI.

Map it to IDTENTRY_RAW to unbreak it. The IDTENTRY_NMI mapping needs to
stay to avoid emitting ASM code.

Fixes: 6271fef00b34 ("x86/entry: Convert NMI to IDTENTRY_NMI")
Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Debugged-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/CA+G9fYvF3cyrY+-iw_SZtpN-i2qA2BruHg4M=QYECU2-dNdsMw@mail.gmail.com
---
 arch/x86/include/asm/idtentry.h | 4 ++--
 arch/x86/kernel/nmi.c           | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 2fc6b0c..cf51c50 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -391,8 +391,8 @@ __visible noinstr void func(struct pt_regs *regs,			\
 #define DEFINE_IDTENTRY_MCE		DEFINE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_MCE_USER	DEFINE_IDTENTRY_NOIST
 
-#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_IST
-#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_IST
+#define DECLARE_IDTENTRY_NMI		DECLARE_IDTENTRY_RAW
+#define DEFINE_IDTENTRY_NMI		DEFINE_IDTENTRY_RAW
 
 #define DECLARE_IDTENTRY_DEBUG		DECLARE_IDTENTRY_IST
 #define DEFINE_IDTENTRY_DEBUG		DEFINE_IDTENTRY_IST
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 3a98ff3..2de365f 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -476,7 +476,7 @@ static DEFINE_PER_CPU(enum nmi_states, nmi_state);
 static DEFINE_PER_CPU(unsigned long, nmi_cr2);
 static DEFINE_PER_CPU(unsigned long, nmi_dr7);
 
-DEFINE_IDTENTRY_NMI(exc_nmi)
+DEFINE_IDTENTRY_RAW(exc_nmi)
 {
 	if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id()))
 		return;