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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, 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 F21D3C433E0 for ; Mon, 1 Feb 2021 05:19:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B5BC564E2A for ; Mon, 1 Feb 2021 05:19:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229689AbhBAFTB (ORCPT ); Mon, 1 Feb 2021 00:19:01 -0500 Received: from mga17.intel.com ([192.55.52.151]:9252 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229542AbhBAFSy (ORCPT ); Mon, 1 Feb 2021 00:18:54 -0500 IronPort-SDR: /22J0W/X7AnvGjl7xJXZg+C2R/ruTftzSe7Z3psmdF4NBpsm2NGP8297b5Z3JmSPWlE848eMZO PIE2qw1pQUGg== X-IronPort-AV: E=McAfee;i="6000,8403,9881"; a="160401823" X-IronPort-AV: E=Sophos;i="5.79,391,1602572400"; d="scan'208";a="160401823" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Jan 2021 21:17:08 -0800 IronPort-SDR: Dd8+6vNNpkn8FCHCUllE9b5q2m+/PL4s4k/XiV6zG4y7jfOSoM7u8G+Ozc8yaFhoTsPq5g4+Z9 D5FLk+bZZbwQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,391,1602572400"; d="scan'208";a="390694252" Received: from clx-ap-likexu.sh.intel.com ([10.239.48.108]) by orsmga008.jf.intel.com with ESMTP; 31 Jan 2021 21:17:04 -0800 From: Like Xu To: Paolo Bonzini , Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , ak@linux.intel.com, wei.w.wang@intel.com, kan.liang@intel.com, alex.shi@linux.alibaba.com, kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v14 00/11] KVM: x86/pmu: Guest Last Branch Recording Enabling Date: Mon, 1 Feb 2021 13:10:28 +0800 Message-Id: <20210201051039.255478-1-like.xu@linux.intel.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi geniuses, Please help review this new version which enables the guest LBR. We already upstreamed the guest LBR support in the host perf, please check more details in each commit and feel free to test and comment. QEMU part: https://lore.kernel.org/qemu-devel/20210201045453.240258-1-like.xu@linux.intel.com kvm-unit-tests: https://lore.kernel.org/kvm/20210201045751.243231-1-like.xu@linux.intel.com v13-v14 Changelog: - Rewrite crud about vcpu->arch.perf_capabilities; - Add PERF_CAPABILITIES testcases to tools/testing/selftests/kvm; - Add basic LBR testcases to the kvm-unit-tests (w/ QEMU patches); - Apply rewritten commit log from Paolo; - Queued the first patch "KVM: x86: Move common set/get handler ..."; - Rename 'already_passthrough' to 'msr_passthrough'; - Check the values of MSR_IA32_PERF_CAPABILITIES early; - Call kvm_x86_ops.pmu_ops->cleanup() always and drop extra_cleanup; - Use INTEL_PMC_IDX_FIXED_VLBR directly; - Fix a bug in the vmx_get_perf_capabilities(); Previous: https://lore.kernel.org/kvm/20210108013704.134985-1-like.xu@linux.intel.com/ --- The last branch recording (LBR) is a performance monitor unit (PMU) feature on Intel processors that records a running trace of the most recent branches taken by the processor in the LBR stack. This patch series is going to enable this feature for plenty of KVM guests. with this patch set, the following error will be gone forever and cloud developers can better understand their programs with less profiling overhead: $ perf record -b lbr ${WORKLOAD} or $ perf record --call-graph lbr ${WORKLOAD} Error: cycles: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat' The user space could configure whether it's enabled or not for each guest via MSR_IA32_PERF_CAPABILITIES msr. As a first step, a guest could only enable LBR feature if its cpu model is the same as the host since the LBR feature is still one of model specific features. If it's enabled on the guest, the guest LBR driver would accesses the LBR MSR (including IA32_DEBUGCTLMSR and records MSRs) as host does. The first guest access on the LBR related MSRs is always interceptible. The KVM trap would create a special LBR event (called guest LBR event) which enables the callstack mode and none of hardware counter is assigned. The host perf would enable and schedule this event as usual. Guest's first access to a LBR registers gets trapped to KVM, which creates a guest LBR perf event. It's a regular LBR perf event which gets the LBR facility assigned from the perf subsystem. Once that succeeds, the LBR stack msrs are passed through to the guest for efficient accesses. However, if another host LBR event comes in and takes over the LBR facility, the LBR msrs will be made interceptible, and guest following accesses to the LBR msrs will be trapped and meaningless. Because saving/restoring tens of LBR MSRs (e.g. 32 LBR stack entries) in VMX transition brings too excessive overhead to frequent vmx transition itself, the guest LBR event would help save/restore the LBR stack msrs during the context switching with the help of native LBR event callstack mechanism, including LBR_SELECT msr. If the guest no longer accesses the LBR-related MSRs within a scheduling time slice and the LBR enable bit is unset, vPMU would release its guest LBR event as a normal event of a unused vPMC and the pass-through state of the LBR stack msrs would be canceled. --- LBR testcase: echo 1 > /proc/sys/kernel/watchdog echo 25 > /proc/sys/kernel/perf_cpu_time_max_percent echo 5000 > /proc/sys/kernel/perf_event_max_sample_rate echo 0 > /proc/sys/kernel/perf_cpu_time_max_percent perf record -b ./br_instr a (perf record --call-graph lbr ./br_instr a) - Perf report on the host: Samples: 72K of event 'cycles', Event count (approx.): 72512 Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycles 12.12% br_instr br_instr [.] cmp_end [.] lfsr_cond 1 11.05% br_instr br_instr [.] lfsr_cond [.] cmp_end 5 8.81% br_instr br_instr [.] lfsr_cond [.] cmp_end 4 5.04% br_instr br_instr [.] cmp_end [.] lfsr_cond 20 4.92% br_instr br_instr [.] lfsr_cond [.] cmp_end 6 4.88% br_instr br_instr [.] cmp_end [.] lfsr_cond 6 4.58% br_instr br_instr [.] cmp_end [.] lfsr_cond 5 - Perf report on the guest: Samples: 92K of event 'cycles', Event count (approx.): 92544 Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycles 12.03% br_instr br_instr [.] cmp_end [.] lfsr_cond 1 11.09% br_instr br_instr [.] lfsr_cond [.] cmp_end 5 8.57% br_instr br_instr [.] lfsr_cond [.] cmp_end 4 5.08% br_instr br_instr [.] lfsr_cond [.] cmp_end 6 5.06% br_instr br_instr [.] cmp_end [.] lfsr_cond 20 4.87% br_instr br_instr [.] cmp_end [.] lfsr_cond 6 4.70% br_instr br_instr [.] cmp_end [.] lfsr_cond 5 Conclusion: the profiling results on the guest are similar to that on the host. Like Xu (11): KVM: x86/vmx: Make vmx_set_intercept_for_msr() non-static KVM: x86/pmu: Set up IA32_PERF_CAPABILITIES if PDCM bit is available KVM: vmx/pmu: Add PMU_CAP_LBR_FMT check when guest LBR is enabled KVM: vmx/pmu: Expose DEBUGCTLMSR_LBR in the MSR_IA32_DEBUGCTLMSR KVM: vmx/pmu: Create a guest LBR event when vcpu sets DEBUGCTLMSR_LBR KVM: vmx/pmu: Pass-through LBR msrs when the guest LBR event is ACTIVE KVM: vmx/pmu: Reduce the overhead of LBR pass-through or cancellation KVM: vmx/pmu: Emulate legacy freezing LBRs on virtual PMI KVM: vmx/pmu: Release guest LBR event via lazy release mechanism KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES selftests: kvm/x86: add test for pmu msr MSR_IA32_PERF_CAPABILITIES arch/x86/kvm/pmu.c | 8 +- arch/x86/kvm/pmu.h | 2 + arch/x86/kvm/vmx/capabilities.h | 19 +- arch/x86/kvm/vmx/pmu_intel.c | 281 +++++++++++++++++- arch/x86/kvm/vmx/vmx.c | 55 +++- arch/x86/kvm/vmx/vmx.h | 28 ++ arch/x86/kvm/x86.c | 2 +- tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/x86_64/vmx_pmu_msrs_test.c | 149 ++++++++++ 10 files changed, 524 insertions(+), 22 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c -- 2.29.2