From patchwork Wed Apr 24 19:32:47 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fenghua Yu X-Patchwork-Id: 10915649 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 A2070922 for ; Wed, 24 Apr 2019 19:44:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 91BE028B8A for ; Wed, 24 Apr 2019 19:44:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8537F28B8E; Wed, 24 Apr 2019 19:44:10 +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 A841228B24 for ; Wed, 24 Apr 2019 19:44:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729695AbfDXToC (ORCPT ); Wed, 24 Apr 2019 15:44:02 -0400 Received: from mga09.intel.com ([134.134.136.24]:15194 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729281AbfDXTlm (ORCPT ); Wed, 24 Apr 2019 15:41:42 -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 orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Apr 2019 12:41:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,390,1549958400"; d="scan'208";a="340454864" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga005.fm.intel.com with ESMTP; 24 Apr 2019 12:41:39 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Paolo Bonzini" , "Dave Hansen" , "Ashok Raj" , "Peter Zijlstra" , "Ravi V Shankar" , "Xiaoyao Li " , "Christopherson Sean J" , "Kalle Valo" , "Michael Chan" Cc: "linux-kernel" , "x86" , kvm@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, Fenghua Yu Subject: [PATCH v8 00/15] x86/split_lock: Enable split lock detection Date: Wed, 24 Apr 2019 12:32:47 -0700 Message-Id: <1556134382-58814-1-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP ==Introduction== A split lock is any atomic operation whose operand crosses two cache lines. Since the operand spans two cache lines and the operation must be atomic, the system locks the bus while the CPU accesses the two cache lines. During bus locking, request from other CPUs or bus agents for control of the bus are blocked. Blocking bus access from other CPUs plus overhead of configuring bus locking protocol degrade not only performance on one CPU but also overall system performance. If the operand is cacheable and completely contained in one cache line, the atomic operation is optimized by less expensive cache locking on Intel P6 and recent processors. If a split lock operation is detected and a developer fixes the issue so that the operand can be operated in one cache line, cache locking instead of more expensive bus locking will be used for the atomic operation. Removing the split lock can improve overall performance. Instructions that may cause split lock issue include lock add, lock btc, xchg, lsl, far call, ltr, etc. More information about split lock, bus locking, and cache locking can be found in the latest Intel 64 and IA-32 Architecture Software Developer's Manual. ==Split lock detection== Currently Linux can trace split lock event counter sq_misc.split_lock for debug purpose. But for system deployed in the field, this event counter after the fact is insufficient. We need a mechanism that detects split lock before it happens to ensure that bus lock is never incurred due to split lock. Intel introduces a mechanism to detect split lock via Alignment Check (#AC) exception before badly aligned atomic instructions might impact whole system performance in Tremont and other future processors. This capability is critical for real time system designers who build consolidated real time systems. These systems run hard real time code on some cores and run "untrusted" user processes on some other cores. The hard real time cannot afford to have any bus lock from the untrusted processes to hurt real time performance. To date the designers have been unable to deploy these solutions as they have no way to prevent the "untrusted" user code from generating split lock and bus lock to block the hard real time code to access memory during bus locking. This capability may also find usage in cloud. A user process with split lock running in one guest can block other cores from accessing shared memory during its split locked memory access. That may cause overall system performance degradation. Split lock may open a security hole where malicious user code may slow down overall system by executing instructions with split lock. ==Enumerate split lock detection feature== A control bit (bit 29) in MSR_TEST_CTL (0x33) will be introduced in future x86 processors. When the bit 29 is set, the processor causes #AC exception for split locked accesses at all CPL. The split lock detection feature is enumerated through bit 5 in MSR_IA32_CORE_CAPABILITY (0xcf). The MSR 0xcf itself is enumerated by CPUID.(EAX=0x7,ECX=0):EDX[30]. The enumeration method is published in the latest Intel 64 and IA-32 Architecture Software Developer's Manual. A few processors have the split lock detection feature. But they don't have MSR_IA32_CORE_CAPABILITY to enumerate the feature. On those processors, enumerate the split lock detection feature based on their family/model/stepping numbers. ==Handle split lock=== There may be different considerations to handle split lock, e.g. how to handle split lock issue in firmware after kernel enables the feature. But this patch set uses a simple way to handle split lock which is suggested by Thomas Gleixner and Dave Hansen: - If split lock happens in kernel, a warning is issued and split lock detection is disabled on the current CPU. The split lock issue should be fixed in kernel. - If split lock happens in user process, the process is killed by SIGBUS. Unless the issue is fixed, the process cannot run in the system. - If split lock happens in firmware, system may hang in firmware. The issue should be fixed in firmware. - Enable split lock detection by default once the feature is enumerated. - Disable split lock detection by kernel parameter "nosplit_lock_detect" during boot time. - Disable/enable split lock detection by sysfs interface /sys/devices/system/cpu/split_lock_detect during run time. ==Expose to guest== To expose this feature to guest, need to 1. Report the new CPUID bit to guest. 2. Emulate IA32_CORE_CAPABILITIES MSR. 3. Emulate TEST_CTL MSR. Since this patch series enable split lock detection in host kernel by default, if do not emulate MSR_TEST_CTL for guest, guest will run with the value set by host without knowing that. So guest will run with split lock detection enabled due to the host's value. Thus guest running with buggy firmware and old kernel will fail because they lack the ability to handle #AC for split lock. So need to emulate MSR_TEST_CTL and separate its value between host and guest. ==Patches== Patch 1-4: Fix a few existing split lock issues. Patch 5-9: Enumerate features and define MSR_TEST_CTL. Patch 10: Handle #AC for split lock. Patch 11-12: Enable split lock detection in KVM. Patch 13: Enable split lock detection by default after #AC handler and KVM are installed. Patch 14: Disable split lock detection by kernel parameter "nosplit_lock_detect" during boot time. Patch 15: Define a sysfs interface to enable/disable split lock detection during run time. ==Changelog== v8: Address issues pointed out by Thomas Gleixner: - Remove all "clearcpuid=" related patches. - Add kernel parameter "nosplit_lock_detect" patch. - Merge definition and initialization of msr_test_ctl_cache into #AC handling patch which first uses the variable. - Add justification for the sysfs knob and combine function and doc patches into one patch 0015. - A few other adjustments. v7: - Add per cpu variable to cach MSR TEST_CTL. Suggested by Thomas Gleixner. - Change a few other changes including locking, simplifying code, work flow, KVM fixes, etc. Suggested by Thomas Gleixner. - Fix KVM issues pointed out by Sean Christopherson. v6: - Fix #AC handler issues pointed out by Dave Hansen - Add doc for the sysfs interface pointed out by Dave Hansen - Fix a lock issue around wrmsr during split lock init, pointed out by Dave Hansen - Update descriptions and comments suggested by Dave Hansen - Fix __le32 issue in wlcore raised by Kalle Valo - Add feature enumeration based on family/model/stepping for Icelake mobile v5: - Fix wlcore issue from Paolo Bonzini - Fix b44 issue from Peter Zijlstra - Change init sequence by Dave Hansen - Fix KVM issues from Paolo Bonzini - Re-order patch sequence v4: - Remove "setcpuid=" option - Enable IA32_CORE_CAPABILITY enumeration for split lock - Handle CPUID faulting by Peter Zijlstra - Enable /sys interface to enable/disable split lock detection v3: - Handle split lock as suggested by Thomas Gleixner. - Fix a few potential spit lock issues suggested by Thomas Gleixner. - Support kernel option "setcpuid=" suggested by Dave Hanson and Thomas Gleixner. - Support flag string in "clearcpuid=" suggested by Dave Hanson and Thomas Gleixner. v2: - Remove code that handles split lock issue in firmware and fix x86_capability issue mainly based on comments from Thomas Gleixner and Peter Zijlstra. In previous version: Comments from Dave Hansen: - Enumerate feature in X86_FEATURE_SPLIT_LOCK_AC - Separate #AC handler from do_error_trap - Use CONFIG to configure inherit BIOS setting, enable, or disable split lock. Remove kernel parameter "split_lock_ac=" - Change config interface to debugfs from sysfs - Fix a few bisectable issues - Other changes. Comment from Tony Luck and Dave Hansen: - Dump right information in #AC handler Comment from Alan Cox and Dave Hansen: - Description of split lock in patch 0 Others: - Remove tracing because we can trace split lock in existing sq_misc.split_lock. - Add CONFIG to configure either panic or re-execute faulting instruction for split lock in kernel. - other minor changes. Fenghua Yu (11): x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long x86/split_lock: Align x86_capability to unsigned long to avoid split locked access x86/msr-index: Define MSR_IA32_CORE_CAPABILITY and split lock detection bit x86/cpufeatures: Enumerate MSR_IA32_CORE_CAPABILITY x86/split_lock: Enumerate split lock detection by MSR_IA32_CORE_CAPABILITY x86/split_lock: Enumerate split lock detection on Icelake mobile processor x86/split_lock: Define MSR TEST_CTL register x86/split_lock: Handle #AC exception for split lock x86/split_lock: Enable split lock detection by default x86/split_lock: Disable split lock detection by kernel parameter "nosplit_lock_detect" x86/split_lock: Add a sysfs interface to enable/disable split lock detection during run time Paolo Bonzini (1): wlcore: simplify/fix/optimize reg_ch_conf_pending operations Peter Zijlstra (1): drivers/net/b44: Align pwol_mask to unsigned long for better performance Xiaoyao Li (2): kvm/x86: Emulate MSR IA32_CORE_CAPABILITY kvm/vmx: Emulate MSR TEST_CTL .../ABI/testing/sysfs-devices-system-cpu | 22 +++ .../admin-guide/kernel-parameters.txt | 2 + arch/x86/include/asm/cpu.h | 8 ++ arch/x86/include/asm/cpufeatures.h | 2 + arch/x86/include/asm/kvm_host.h | 1 + arch/x86/include/asm/msr-index.h | 7 + arch/x86/include/asm/processor.h | 4 +- arch/x86/kernel/cpu/common.c | 7 +- arch/x86/kernel/cpu/cpuid-deps.c | 79 ++++++----- arch/x86/kernel/cpu/intel.c | 133 ++++++++++++++++++ arch/x86/kernel/traps.c | 31 +++- arch/x86/kvm/cpuid.c | 6 + arch/x86/kvm/vmx/vmx.c | 42 ++++++ arch/x86/kvm/vmx/vmx.h | 2 + arch/x86/kvm/x86.c | 39 +++++ drivers/net/ethernet/broadcom/b44.c | 4 +- drivers/net/wireless/ti/wlcore/cmd.c | 15 +- drivers/net/wireless/ti/wlcore/wlcore.h | 4 +- 18 files changed, 352 insertions(+), 56 deletions(-)