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Date: Wed, 19 May 2021 09:44:24 +0800 From: Liuxiangdong <liuxiangdong5@...wei.com> To: "Xu, Like" <like.xu@...el.com> CC: Borislav Petkov <bp@...en8.de>, Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, <weijiang.yang@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, <ak@...ux.intel.com>, <wei.w.wang@...el.com>, <eranian@...gle.com>, <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <kvm@...r.kernel.org>, "Fangyi (Eric)" <eric.fangyi@...wei.com>, Xiexiangyou <xiexiangyou@...wei.com>, Peter Zijlstra <peterz@...radead.org>, "Paolo Bonzini" <pbonzini@...hat.com>, Like Xu <like.xu@...ux.intel.com> Subject: Re: [PATCH v6 00/16] KVM: x86/pmu: Add *basic* support to enable guest PEBS via DS On 2021/5/18 20:40, Xu, Like wrote: > On 2021/5/18 20:23, Liuxiangdong wrote: >> >> >> On 2021/5/17 14:38, Like Xu wrote: >>> Hi xiangdong, >>> >>> On 2021/5/15 18:30, Liuxiangdong wrote: >>>> >>>> >>>> On 2021/5/11 10:41, Like Xu wrote: >>>>> A new kernel cycle has begun, and this version looks promising. >>>>> >>>>> The guest Precise Event Based Sampling (PEBS) feature can provide >>>>> an architectural state of the instruction executed after the guest >>>>> instruction that exactly caused the event. It needs new hardware >>>>> facility only available on Intel Ice Lake Server platforms. This >>>>> patch set enables the basic PEBS feature for KVM guests on ICX. >>>>> >>>>> We can use PEBS feature on the Linux guest like native: >>>>> >>>>> # perf record -e instructions:ppp ./br_instr a >>>>> # perf record -c 100000 -e instructions:pp ./br_instr a >>>> >>>> Hi, Like. >>>> Has the qemu patch been modified? >>>> >>>> https://lore.kernel.org/kvm/f4dcb068-2ddf-428f-50ad-39f65cad3710@intel.com/ >>>> ? >>> >>> I think the qemu part still works based on >>> 609d7596524ab204ccd71ef42c9eee4c7c338ea4 (tag: v6.0.0). >>> >> >> Yes. I applied these two qemu patches to qemu v6.0.0 and this kvm >> patches set to latest kvm tree. >> >> I can see pebs flags in Guest(linux 5.11) on the IceLake( Model: 106 >> Model name: Intel(R) Xeon(R) Platinum 8378A CPU), >> and i can use PEBS like this. >> >> #perf record -e instructions:pp >> >> It can work normally. >> >> But there is no sampling when i use "perf record -e events:pp" or >> just "perf record" in guest >> unless i delete patch 09 and patch 13 from this kvm patches set. >> >> > > With patch 9 and 13, does the basic counter sampling still work ? > You may retry w/ "echo 0 > /proc/sys/kernel/watchdog" on the host and > guest. > In fact, I didn't use "echo 0 > /proc/sys/kernel/watchdog" when I tried PEBS patches V3 on Icelake. Why should we use it now? What does it have to do with sampling? Thanks! >> Have you tried "perf record -e events:pp" in this patches set? Does >> it work normally? > > All my PEBS testcases passed. You may dump guest msr traces from your > testcase with me. > >> >> >> >> Thanks! >> Xiangdong Liu >> >> >> >>> When the LBR qemu patch receives the ACK from the maintainer, >>> I will submit PBES qemu support because their changes are very similar. >>> >>> Please help review this version and >>> feel free to add your comments or "Reviewed-by". >>> >>> Thanks, >>> Like Xu >>> >>>> >>>> >>>>> To emulate guest PEBS facility for the above perf usages, >>>>> we need to implement 2 code paths: >>>>> >>>>> 1) Fast path >>>>> >>>>> This is when the host assigned physical PMC has an identical index as >>>>> the virtual PMC (e.g. using physical PMC0 to emulate virtual PMC0). >>>>> This path is used in most common use cases. >>>>> >>>>> 2) Slow path >>>>> >>>>> This is when the host assigned physical PMC has a different index >>>>> from the virtual PMC (e.g. using physical PMC1 to emulate virtual >>>>> PMC0) >>>>> In this case, KVM needs to rewrite the PEBS records to change the >>>>> applicable counter indexes to the virtual PMC indexes, which would >>>>> otherwise contain the physical counter index written by PEBS >>>>> facility, >>>>> and switch the counter reset values to the offset corresponding to >>>>> the physical counter indexes in the DS data structure. >>>>> >>>>> The previous version [0] enables both fast path and slow path, which >>>>> seems a bit more complex as the first step. In this patchset, we want >>>>> to start with the fast path to get the basic guest PEBS enabled while >>>>> keeping the slow path disabled. More focused discussion on the slow >>>>> path [1] is planned to be put to another patchset in the next step. >>>>> >>>>> Compared to later versions in subsequent steps, the functionality >>>>> to support host-guest PEBS both enabled and the functionality to >>>>> emulate guest PEBS when the counter is cross-mapped are missing >>>>> in this patch set (neither of these are typical scenarios). >>>>> >>>>> With the basic support, the guest can retrieve the correct PEBS >>>>> information from its own PEBS records on the Ice Lake servers. >>>>> And we expect it should work when migrating to another Ice Lake >>>>> and no regression about host perf is expected. >>>>> >>>>> Here are the results of pebs test from guest/host for same workload: >>>>> >>>>> perf report on guest: >>>>> # Samples: 2K of event 'instructions:ppp', # Event count >>>>> (approx.): 1473377250 >>>>> # Overhead Command Shared Object Symbol >>>>> 57.74% br_instr br_instr [.] lfsr_cond >>>>> 41.40% br_instr br_instr [.] cmp_end >>>>> 0.21% br_instr [kernel.kallsyms] [k] __lock_acquire >>>>> >>>>> perf report on host: >>>>> # Samples: 2K of event 'instructions:ppp', # Event count >>>>> (approx.): 1462721386 >>>>> # Overhead Command Shared Object Symbol >>>>> 57.90% br_instr br_instr [.] lfsr_cond >>>>> 41.95% br_instr br_instr [.] cmp_end >>>>> 0.05% br_instr [kernel.vmlinux] [k] lock_acquire >>>>> Conclusion: the profiling results on the guest are similar >>>>> tothat on the host. >>>>> >>>>> A minimum guest kernel version may be v5.4 or a backport version >>>>> support Icelake server PEBS. >>>>> >>>>> Please check more details in each commit and feel free to comment. >>>>> >>>>> Previous: >>>>> https://lore.kernel.org/kvm/20210415032016.166201-1-like.xu@linux.intel.com/ >>>>> >>>>> >>>>> [0] >>>>> https://lore.kernel.org/kvm/20210104131542.495413-1-like.xu@linux.intel.com/ >>>>> [1] >>>>> https://lore.kernel.org/kvm/20210115191113.nktlnmivc3edstiv@two.firstfloor.org/ >>>>> >>>>> >>>>> V5 -> V6 Changelog: >>>>> - Rebased on the latest kvm/queue tree; >>>>> - Fix a git rebase issue (Liuxiangdong); >>>>> - Adjust the patch sequence 06/07 for bisection (Liuxiangdong); >>>>> >>>>> Like Xu (16): >>>>> perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server >>>>> perf/x86/intel: Handle guest PEBS overflow PMI for KVM guest >>>>> perf/x86/core: Pass "struct kvm_pmu *" to determine the guest >>>>> values >>>>> KVM: x86/pmu: Set MSR_IA32_MISC_ENABLE_EMON bit when vPMU is >>>>> enabled >>>>> KVM: x86/pmu: Introduce the ctrl_mask value for fixed counter >>>>> KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS >>>>> KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter >>>>> KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS >>>>> KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support >>>>> adaptive PEBS >>>>> KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is >>>>> enabled >>>>> KVM: x86/pmu: Adjust precise_ip to emulate Ice Lake guest PDIR >>>>> counter >>>>> KVM: x86/pmu: Move pmc_speculative_in_use() to arch/x86/kvm/pmu.h >>>>> KVM: x86/pmu: Disable guest PEBS temporarily in two rare >>>>> situations >>>>> KVM: x86/pmu: Add kvm_pmu_cap to optimize >>>>> perf_get_x86_pmu_capability >>>>> KVM: x86/cpuid: Refactor host/guest CPU model consistency check >>>>> KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64 >>>>> >>>>> arch/x86/events/core.c | 5 +- >>>>> arch/x86/events/intel/core.c | 129 >>>>> ++++++++++++++++++++++++------ >>>>> arch/x86/events/perf_event.h | 5 +- >>>>> arch/x86/include/asm/kvm_host.h | 16 ++++ >>>>> arch/x86/include/asm/msr-index.h | 6 ++ >>>>> arch/x86/include/asm/perf_event.h | 5 +- >>>>> arch/x86/kvm/cpuid.c | 24 ++---- >>>>> arch/x86/kvm/cpuid.h | 5 ++ >>>>> arch/x86/kvm/pmu.c | 50 +++++++++--- >>>>> arch/x86/kvm/pmu.h | 38 +++++++++ >>>>> arch/x86/kvm/vmx/capabilities.h | 26 ++++-- >>>>> arch/x86/kvm/vmx/pmu_intel.c | 115 +++++++++++++++++++++----- >>>>> arch/x86/kvm/vmx/vmx.c | 24 +++++- >>>>> arch/x86/kvm/vmx/vmx.h | 2 +- >>>>> arch/x86/kvm/x86.c | 14 ++-- >>>>> 15 files changed, 368 insertions(+), 96 deletions(-) >>>>> >>> >> >
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