From patchwork Tue Mar 12 23:00:27 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fenghua Yu X-Patchwork-Id: 10850121 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5E0411515 for ; Tue, 12 Mar 2019 23:08:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 494A028749 for ; Tue, 12 Mar 2019 23:08:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3C2212993B; Tue, 12 Mar 2019 23:08:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2A72F28749 for ; Tue, 12 Mar 2019 23:08:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727486AbfCLXIU (ORCPT ); Tue, 12 Mar 2019 19:08:20 -0400 Received: from mga11.intel.com ([192.55.52.93]:27628 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727328AbfCLXIR (ORCPT ); Tue, 12 Mar 2019 19:08:17 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Mar 2019 16:08:14 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,472,1544515200"; d="scan'208";a="326744240" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga006.fm.intel.com with ESMTP; 12 Mar 2019 16:08:14 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "H Peter Anvin" , "Dave Hansen" , "Paolo Bonzini" , "Ashok Raj" , "Peter Zijlstra" , "Xiaoyao Li " , "Michael Chan" , "Ravi V Shankar" Cc: "linux-kernel" , "x86" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, Fenghua Yu Subject: [PATCH v5 09/18] x86/split_lock: Handle #AC exception for split lock Date: Tue, 12 Mar 2019 16:00:27 -0700 Message-Id: <1552431636-31511-10-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1552431636-31511-1-git-send-email-fenghua.yu@intel.com> References: <1552431636-31511-1-git-send-email-fenghua.yu@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There may be different considerations on how to handle #AC for split lock, e.g. how to handle system hang caused by split lock issue in firmware, how to emulate faulting instruction, etc. We use a simple method to handle user and kernel split lock and may extend the method in the future. When #AC exception for split lock is triggered from user process, the process is killed by SIGBUS. To execute the process properly, user application developer needs to fix the split lock issue. When #AC exception for split lock is triggered from a kernel instruction, disable #AC for split lock on local CPU and warn the split lock issue. After the exception, the faulting instruction will be executed and kernel execution continues. #AC for split lock is only disabled on the local CPU not globally. It will be re-enabled if the CPU is offline and then online. Kernel developer should check the warning, which contains helpful faulting address, context, and callstack info, and fix the split lock issue one by one. Then further split lock may be captured and fixed. After bit 29 in MSR_TEST_CTL is set as one in kernel, firmware inherits the setting when firmware is executed in S4, S5, run time services, SMI, etc. Split lock issue in firmware triggers #AC and may hang the system depending on how firmware handles the #AC. It's up to firmware developer to fix the split lock issues in firmware. Signed-off-by: Fenghua Yu --- arch/x86/kernel/traps.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index d26f9e9c3d83..69b6233e783e 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -61,6 +61,7 @@ #include #include #include +#include #ifdef CONFIG_X86_64 #include @@ -293,7 +294,37 @@ DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, 0, NULL, "coprocessor segment overru DO_ERROR(X86_TRAP_TS, SIGSEGV, 0, NULL, "invalid TSS", invalid_TSS) DO_ERROR(X86_TRAP_NP, SIGBUS, 0, NULL, "segment not present", segment_not_present) DO_ERROR(X86_TRAP_SS, SIGBUS, 0, NULL, "stack segment", stack_segment) +#ifndef CONFIG_CPU_SUP_INTEL DO_ERROR(X86_TRAP_AC, SIGBUS, BUS_ADRALN, NULL, "alignment check", alignment_check) +#else +dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code) +{ + unsigned int trapnr = X86_TRAP_AC; + char str[] = "alignment check"; + int signr = SIGBUS; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); + + if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != + NOTIFY_STOP) { + cond_local_irq_enable(regs); + if (!user_mode(regs)) { + /* + * Only split lock can generate #AC from kernel. Warn + * and disable #AC for split lock on current CPU. + */ + msr_clear_bit(MSR_TEST_CTL, + TEST_CTL_ENABLE_SPLIT_LOCK_DETECT_SHIFT); + WARN_ONCE(1, "A split lock issue is detected.\n"); + + return; + } + /* Handle #AC generated from user code. */ + do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs, + error_code, BUS_ADRALN, NULL); + } +} +#endif #undef IP #ifdef CONFIG_VMAP_STACK