From: Chunyu Hu <chuhu@redhat.com>
Date: Mon, 27 Nov 2017 22:21:39 +0800
Subject: x86/idt: Load idt early in start_secondary
Git-commit: 55d2d0ad2fb4325f615d1950486fbc5e6fba1769
Patch-mainline: v4.15-rc3
References: bsc#1110006

On a secondary, idt is first loaded in cpu_init() with load_current_idt(),
i.e. no exceptions can be handled before that point.

The conversion of WARN() to use UD requires the IDT being loaded earlier as
any warning between start_secondary() and load_curren_idt() in cpu_init()
will result in an unhandled @UD exception and therefore fail the bringup of
the CPU.

Install the IDT handlers right in start_secondary() before calling cpu_init().

[ tglx: Massaged changelog ]

Fixes: 9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Cc: peterz@infradead.org
Cc: bp@alien8.de
Cc: rostedt@goodmis.org
Cc: luto@kernel.org
Link: https://lkml.kernel.org/r/1511792499-4073-1-git-send-email-chuhu@redhat.com

Acked-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/smpboot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -230,6 +230,7 @@ static void notrace start_secondary(void
 	 */
 	if (boot_cpu_has(X86_FEATURE_PCID))
 		__write_cr4(__read_cr4() | X86_CR4_PCIDE);
+	load_current_idt();
 	cpu_init();
 	x86_cpuinit.early_percpu_clock_init();
 	preempt_disable();