From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752588AbdK0OVs (ORCPT ); Mon, 27 Nov 2017 09:21:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38512 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751311AbdK0OVp (ORCPT ); Mon, 27 Nov 2017 09:21:45 -0500 From: Chunyu Hu To: tglx@linutronix.de Cc: mingo@kernel.org, hpa@zytor.com, peterz@infradead.org, luto@kernel.org, bp@alien8.de, rostedt@goodmis.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/idt: load idt early in start_secondary Date: Mon, 27 Nov 2017 22:21:39 +0800 Message-Id: <1511792499-4073-1-git-send-email-chuhu@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 27 Nov 2017 14:21:45 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For ap, idt is first loaded in cpu_init() with load_current_idt(), that is to say, no exception can be handled before there. And then the idt_table has been completed by the bp. While there are some WARNs which needs the UD exception handling in the early boot code might be triggered when something uexpected happens during boot. In that case, cpu would fail to boot as the exception can't be handled. A WARNing during boot is not usually meaning the system could not boot. One use case is when ftrace=function is setup in kernel cmdline, the ftrace callback function will be called for every traced function. And in my case, the first traced function is load_ucode_ap. And there are WARN()s in function trace callback handling, it failed to reboot as one of the WARN()s is triggered before load_current_idt() executed. To make WARN()s can work earlier to ap, we load the idt_table early in start_secondary, and keep the second time idt load in cpu_init, as there is a load_ucode_ap() there. Signed-off-by: Chunyu Hu --- arch/x86/kernel/smpboot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 3d01df7..05a97d5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -237,7 +237,7 @@ 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(); -- 1.8.3.1