From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752443AbeENSz3 (ORCPT ); Mon, 14 May 2018 14:55:29 -0400 Received: from mga06.intel.com ([134.134.136.31]:55033 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751954AbeENSw3 (ORCPT ); Mon, 14 May 2018 14:52:29 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.49,401,1520924400"; d="scan'208";a="39244624" From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "H. Peter Anvin" , "Ashok Raj" , "Ravi V Shankar" , "Tony Luck" , "Dave Hansen" , "Rafael Wysocki" , "Arjan van de Ven" , "Alan Cox" Cc: "x86" , "linux-kernel" , Fenghua Yu Subject: [PATCH 02/15] x86/split_lock: Set up #AC exception for split locked accesses Date: Mon, 14 May 2018 11:52:12 -0700 Message-Id: <1526323945-211107-3-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1526323945-211107-1-git-send-email-fenghua.yu@intel.com> References: <1526323945-211107-1-git-send-email-fenghua.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When bit 29 is set in Test Control MSR register 0x33, #AC exception is generated for split locked accesses at all CPL. By default, kernel inherits the bit setting from BIOS. Signed-off-by: Fenghua Yu --- arch/x86/include/asm/cpu.h | 2 ++ arch/x86/kernel/cpu/common.c | 2 ++ arch/x86/kernel/cpu/split_lock.c | 54 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 58 insertions(+) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index c73b6d369047..b4fe6496bb15 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -42,7 +42,9 @@ unsigned int x86_model(unsigned int sig); unsigned int x86_stepping(unsigned int sig); #ifdef CONFIG_SPLIT_LOCK_AC int __init enumerate_split_lock(void); +void setup_split_lock(void); #else /* CONFIG_SPLIT_LOCK_AC */ static inline int enumerate_split_lock(void) { return 0; } +static inline void setup_split_lock(void) {} #endif /* CONFIG_SPLIT_LOCK_AC */ #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 7684e82e254f..daff18ef4f8f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1304,6 +1304,8 @@ static void identify_cpu(struct cpuinfo_x86 *c) /* Init Machine Check Exception if available. */ mcheck_cpu_init(c); + setup_split_lock(); + select_idle_routine(c); #ifdef CONFIG_NUMA diff --git a/arch/x86/kernel/cpu/split_lock.c b/arch/x86/kernel/cpu/split_lock.c index 2ab28419e080..98bbfb176cf4 100644 --- a/arch/x86/kernel/cpu/split_lock.c +++ b/arch/x86/kernel/cpu/split_lock.c @@ -15,6 +15,11 @@ static bool split_lock_ac_supported; +#define DISABLE_SPLIT_LOCK_AC 0 +#define ENABLE_SPLIT_LOCK_AC 1 + +static int split_lock_ac = DISABLE_SPLIT_LOCK_AC; + /* * On processors not supporting #AC exception for split lock feature, * MSR_TEST_CTL may not exist or MSR_TEST_CTL exists but the bit 29 is @@ -58,5 +63,54 @@ void __init enumerate_split_lock(void) */ wrmsr(MSR_TEST_CTL, l_orig, h); + /* Initialize split lock setting from previous BIOS setting. */ + if (l_orig & MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK) + split_lock_ac = ENABLE_SPLIT_LOCK_AC; + else + split_lock_ac = DISABLE_SPLIT_LOCK_AC; + pr_info("#AC exception for split locked accesses is supported\n"); } + +static bool _setup_split_lock(int split_lock_ac_val) +{ + u32 l, h; + + rdmsr(MSR_TEST_CTL, l, h); + + /* No need to update MSR if same value. */ + if ((l >> MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK_SHIFT & 0x1) == + split_lock_ac_val) + goto out; + + if (split_lock_ac_val == ENABLE_SPLIT_LOCK_AC) + /* Set the split lock bit to enable the feature. */ + l |= MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK; + else if (split_lock_ac_val == DISABLE_SPLIT_LOCK_AC) + /* Clear the split lock bit to disable the feature. */ + l &= ~MSR_TEST_CTL_ENABLE_AC_SPLIT_LOCK; + else + return false; + + wrmsr(MSR_TEST_CTL, l, h); +out: + return true; +} + +void setup_split_lock(void) +{ + if (!split_lock_ac_supported) + return; + + if (!_setup_split_lock(split_lock_ac)) + goto out_fail; + + pr_info_once("split lock #AC is %sd\n", + split_lock_ac == ENABLE_SPLIT_LOCK_AC ? "enable" + : "disable"); + + return; + +out_fail: + pr_warn("fail to set split lock #AC\n"); +} -- 2.5.0