Commit 71ed49d8 authored Jun 12, 2020 by Thomas Gleixner

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: 6271fef0 ("x86/entry: Convert NMI to IDTENTRY_NMI")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Debugged-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/CA+G9fYvF3cyrY+-iw_SZtpN-i2qA2BruHg4M=QYECU2-dNdsMw@mail.gmail.com

parent 15a416e8

arch/x86/include/asm/idtentry.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -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

arch/x86/kernel/nmi.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

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