From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 35423470110; Mon, 17 Aug 2026 18:41:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786992090; cv=none; b=J/4+AzPPREUnFyTz1fQD2uj7dXbILD1mTHXPNKrUMjJQ2C3bfRKpPiryciEqzj7ScnHOeJXv+3RHC7OWhUgFzvjP+QQH/af/7uIQYE0BfR4Hy8iYd6zPoaNux/gQI98hJ6mipTZkGn2wd8LzYyKufHvMlAyCtCP7CxvexZKtbcU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786992090; c=relaxed/simple; bh=7enoeOr+5bHlwtkPhEcyQTkoqg1DbtY8tEDKcB319iE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JRErLed52afxvFrPfEdoYuZjGVAeIoOJiRRJbOSeyd/WTcILV3HbkEQ/YjB4OkO40sp7hcAblT1vNUepPLt343zikdLrfHfeXt1c06kSHxWinQrW/s4us73ZiZAd/VEjMd1oMjcAr8lK6aT4BxrfLQ4qNgkI8ZE0dQMHpSnnWXg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=aEX/Np5K; arc=none smtp.client-ip=192.198.163.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="aEX/Np5K" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1786992089; x=1818528089; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=7enoeOr+5bHlwtkPhEcyQTkoqg1DbtY8tEDKcB319iE=; b=aEX/Np5KujO3l/4VNRodIZfywDX19156JW+EhNWOmCGBOGtLKzsIIxos yQ7t1OvbNk6Qg9/RLRhi0bJTVCcXrBwPPFraX7wGIwYv9uKViROR9yzxn 5QXGJZ0AF3XNkJblmnvxEzzs4NAUg9L8RtmeumGNd785IIDrKFHBTwV1T Vtx4rPrfieyPzbHxET5ZETXrPt9DYmpNd1B5Cf/DqyE08M3DAsiCL2BdJ JkTXfahSGu+76vY2I2Iq2eQmuD7bJMAdatmbV9B5i8lm17y7yEEGTFOyw SbGyiUoK1g7fXZAFr9i+aSbivKaXviUMn9jGsRPz2CnlnZOVV4cH+44mz w==; X-CSE-ConnectionGUID: Se1UkMjsRDSc7K4Fsogziw== X-CSE-MsgGUID: K1+pvi5lSP2hBQWDACNT2A== X-IronPort-AV: E=McAfee;i="6800,10657,11878"; a="98066084" X-IronPort-AV: E=Sophos;i="6.25,229,1779174000"; d="scan'208";a="98066084" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2026 11:41:25 -0700 X-CSE-ConnectionGUID: NytYkXPSRg+GGvz9nguNUA== X-CSE-MsgGUID: dbs722HgTJaosJhrxE2y4g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,229,1779174000"; d="scan'208";a="263656959" Received: from 9cc2c43eec6b.jf.intel.com ([10.54.77.29]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Aug 2026 11:41:24 -0700 From: Zide Chen To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, Jim Mattson , Andi Kleen , linux-kernel@vger.kernel.org, Mingwei Zhang , Zide Chen , Das Sandipan , Shukla Manali , Dapeng Mi , Xudong Hao Subject: [PATCH v8 2/8] KVM: x86/pmu: Support Intel fixed counter 3 on mediated vPMU Date: Mon, 17 Aug 2026 11:31:36 -0700 Message-ID: <20260817183143.226156-3-zide.chen@intel.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817183143.226156-1-zide.chen@intel.com> References: <20260817183143.226156-1-zide.chen@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Dapeng Mi Starting with Ice Lake, Intel introduced fixed counter 3, which counts TOPDOWN.SLOTS - the number of available slots for an unhalted logical processor. It serves as the denominator for top-level metrics in the Top-down Microarchitecture Analysis method. Emulating this counter on legacy vPMU would require introducing a new generic perf encoding for the Intel-specific TOPDOWN.SLOTS event in order to call perf_get_hw_event_config(). This is undesirable as it would pollute the generic perf event encoding. Moreover, KVM does not intend to emulate IA32_PERF_METRICS in the legacy vPMU model, and without IA32_PERF_METRICS, emulating this counter has little practical value. Therefore, expose fixed counter 3 to guests only when mediated vPMU is enabled. Signed-off-by: Dapeng Mi Co-developed-by: Zide Chen Signed-off-by: Zide Chen Reviewed-by: Jim Mattson --- v6: - Update comments to replace 2 with KVM_MAX_NR_INTEL_FIXED_COUNTERS - 1. v3: - Move the non-contiguous counter filter code to pmu.c v2: - Don't advertise fixed counter 3 to userspace if the host doesn't support it. --- arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/msrs.c | 4 ++-- arch/x86/kvm/pmu.c | 19 ++++++++++++++++++- 3 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 283847619ff8..8a4e542218a7 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -562,7 +562,7 @@ struct kvm_pmc { #define KVM_MAX_NR_GP_COUNTERS KVM_MAX(KVM_MAX_NR_INTEL_GP_COUNTERS, \ KVM_MAX_NR_AMD_GP_COUNTERS) -#define KVM_MAX_NR_INTEL_FIXED_COUNTERS 3 +#define KVM_MAX_NR_INTEL_FIXED_COUNTERS 4 #define KVM_MAX_NR_AMD_FIXED_COUNTERS 0 #define KVM_MAX_NR_FIXED_COUNTERS KVM_MAX(KVM_MAX_NR_INTEL_FIXED_COUNTERS, \ KVM_MAX_NR_AMD_FIXED_COUNTERS) diff --git a/arch/x86/kvm/msrs.c b/arch/x86/kvm/msrs.c index 66fa7140d65d..1fbd8f08a7f0 100644 --- a/arch/x86/kvm/msrs.c +++ b/arch/x86/kvm/msrs.c @@ -217,7 +217,7 @@ static const u32 msrs_to_save_base[] = { static const u32 msrs_to_save_pmu[] = { MSR_ARCH_PERFMON_FIXED_CTR0, MSR_ARCH_PERFMON_FIXED_CTR1, - MSR_ARCH_PERFMON_FIXED_CTR0 + 2, + MSR_ARCH_PERFMON_FIXED_CTR2, MSR_ARCH_PERFMON_FIXED_CTR3, MSR_CORE_PERF_FIXED_CTR_CTRL, MSR_CORE_PERF_GLOBAL_STATUS, MSR_CORE_PERF_GLOBAL_CTRL, MSR_IA32_PEBS_ENABLE, MSR_IA32_DS_AREA, MSR_PEBS_DATA_CFG, @@ -2671,7 +2671,7 @@ void kvm_init_msr_lists(void) { unsigned i; - BUILD_BUG_ON_MSG(KVM_MAX_NR_FIXED_COUNTERS != 3, + BUILD_BUG_ON_MSG(KVM_MAX_NR_FIXED_COUNTERS != 4, "Please update the fixed PMCs in msrs_to_save_pmu[]"); num_msrs_to_save = 0; diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index a7d60c8785cd..913a0ecbf260 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -19,6 +19,7 @@ #include #include #include +#include #include "x86.h" #include "cpuid.h" #include "lapic.h" @@ -99,7 +100,8 @@ static const struct x86_cpu_id vmx_pebs_pdist_cpu[] = { * all perf counters (both gp and fixed). The mapping relationship * between pmc and perf counters is as the following: * * Intel: [0 .. KVM_MAX_NR_INTEL_GP_COUNTERS-1] <=> gp counters - * [KVM_FIXED_PMC_BASE_IDX .. KVM_FIXED_PMC_BASE_IDX + 2] <=> fixed + * [KVM_FIXED_PMC_BASE_IDX .. KVM_FIXED_PMC_BASE_IDX + + * KVM_MAX_NR_INTEL_FIXED_COUNTERS - 1] <=> fixed * * AMD: [0 .. AMD64_NUM_COUNTERS-1] and, for families 15H * and later, [0 .. AMD64_NUM_COUNTERS_CORE-1] <=> gp counters */ @@ -134,6 +136,8 @@ void kvm_init_pmu_capability(struct kvm_pmu_ops *pmu_ops) { bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL; int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS; + union cpuid10_edx edx; + u32 eax, ebx, ecx; /* * Hybrid PMUs don't play nice with virtualization without careful @@ -181,6 +185,19 @@ void kvm_init_pmu_capability(struct kvm_pmu_ops *pmu_ops) kvm_pmu_cap.num_counters_fixed = min(kvm_pmu_cap.num_counters_fixed, KVM_MAX_NR_FIXED_COUNTERS); + /* + * Currently, KVM doesn't support non-contiguous fixed counters; make + * sure only contiguous ones are retained in kvm_pmu_cap. + */ + if (kvm_host_pmu.version >= 5) { + cpuid(0xa, &eax, &ebx, &ecx, &edx.full); + if (kvm_pmu_cap.num_counters_fixed > edx.split.num_counters_fixed) + kvm_pmu_cap.num_counters_fixed = edx.split.num_counters_fixed; + } + + if (!enable_mediated_pmu && kvm_pmu_cap.num_counters_fixed > 3) + kvm_pmu_cap.num_counters_fixed = 3; + kvm_pmu_eventsel.INSTRUCTIONS_RETIRED = perf_get_hw_event_config(PERF_COUNT_HW_INSTRUCTIONS); kvm_pmu_eventsel.BRANCH_INSTRUCTIONS_RETIRED = -- 2.55.0