[PATCH 4.14 046/164] x86/idt: Load idt early in start_secondary

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Chunyu Hu <chuhu@xxxxxxxxxx>

commit 55d2d0ad2fb4325f615d1950486fbc5e6fba1769 upstream.

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@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: peterz@xxxxxxxxxxxxx
Cc: bp@xxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: luto@xxxxxxxxxx
Link: https://lkml.kernel.org/r/1511792499-4073-1-git-send-email-chuhu@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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
@@ -239,7 +239,7 @@ static void notrace start_secondary(void
 	load_cr3(swapper_pg_dir);
 	__flush_tlb_all();
 #endif
-
+	load_current_idt();
 	cpu_init();
 	x86_cpuinit.early_percpu_clock_init();
 	preempt_disable();