x86/idt: Load idt early in start_secondary

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@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 65a0ccdc3050742f9235922aaa3774560ca1f9c2..5e0453f18a57c88ed20a90ab3fba6a8a0ae1bc2c 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -239,7 +239,7 @@ static void notrace start_secondary(void *unused)
        load_cr3(swapper_pg_dir);
        __flush_tlb_all();
 #endif
-
+       load_current_idt();
        cpu_init();
        x86_cpuinit.early_percpu_clock_init();
        preempt_disable();