From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82FCAC4360F for ; Wed, 3 Apr 2019 21:30:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 543982084B for ; Wed, 3 Apr 2019 21:30:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726890AbfDCVaW (ORCPT ); Wed, 3 Apr 2019 17:30:22 -0400 Received: from mga05.intel.com ([192.55.52.43]:37332 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726790AbfDCVaV (ORCPT ); Wed, 3 Apr 2019 17:30:21 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Apr 2019 14:30:11 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,306,1549958400"; d="scan'208";a="334754249" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga005.fm.intel.com with ESMTP; 03 Apr 2019 14:30:11 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Dave Hansen" , "Paolo Bonzini" , "Ashok Raj" , "Peter Zijlstra" , "Kalle Valo" , "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 v6 10/20] x86/split_lock: Handle #AC exception for split lock Date: Wed, 3 Apr 2019 14:21:56 -0700 Message-Id: <1554326526-172295-11-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> References: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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, a user application developer needs to fix the split lock issue. When #AC exception for split lock is triggered from a kernel instruction, disable split lock detection on local CPU and warn the split lock issue. After the exception, the faulting instruction will be executed and kernel execution continues. Split lock detection is only disabled on the local CPU, not globally. It will be re-enabled if the CPU is offline and then online or through sysfs interface. A kernel/driver developer should check the warning, which contains helpful faulting address, context, and callstack info, and fix the split lock issues. Then further split lock issues may be captured and fixed. After bit 29 in MSR_TEST_CTL is set to 1 in kernel, firmware inherits the setting when firmware is executed in S4, S5, run time services, SMI, etc. If there is a split lock operation in firmware, it will triggers #AC and may hang the system depending on how firmware handles the #AC. It's up to a firmware developer to fix split lock issues in firmware. Signed-off-by: Fenghua Yu --- arch/x86/kernel/traps.c | 43 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index d26f9e9c3d83..0ac992bfa287 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 @@ -293,9 +294,49 @@ 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) -DO_ERROR(X86_TRAP_AC, SIGBUS, BUS_ADRALN, NULL, "alignment check", alignment_check) #undef IP +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"); + + /* + * WARN*()s end up here; fix them up before we call the + * notifier chain. + */ + if (!user_mode(regs) && fixup_bug(regs, trapnr)) + return; + + if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) == + NOTIFY_STOP) + return; + + cond_local_irq_enable(regs); + if (!user_mode(regs) && + static_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) { + /* + * Only split lock can generate #AC from kernel at this point. + * Warn and disable split lock detection on this CPU. The + * faulting instruction will be executed without generating + * another #AC fault. User needs to check the warning and + * fix the split lock issue in the faulting instruction. + */ + msr_clear_bit(MSR_TEST_CTL, + TEST_CTL_ENABLE_SPLIT_LOCK_DETECT_SHIFT); + WARN_ONCE(1, "split lock operation detected\n"); + + return; + } + + /* Handle #AC generated in any other cases. */ + do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs, + error_code, BUS_ADRALN, NULL); +} + #ifdef CONFIG_VMAP_STACK __visible void __noreturn handle_stack_overflow(const char *message, struct pt_regs *regs, -- 2.19.1