From: Like Xu <like.xu@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
ak@linux.intel.com, wei.w.wang@intel.com,
Like Xu <like.xu@linux.intel.com>
Subject: [PATCH v11 11/11] KVM: x86/pmu: Reduce the overhead of LBR passthrough or cancellation
Date: Thu, 14 May 2020 16:30:54 +0800 [thread overview]
Message-ID: <20200514083054.62538-12-like.xu@linux.intel.com> (raw)
In-Reply-To: <20200514083054.62538-1-like.xu@linux.intel.com>
After passthrough the LBR msrs to the guest, there is no need to call
intel_pmu_intercept_lbr_msrs() again and again, and vice versa.
If host reclaims the LBR between two availability checks, the interception
state and LBR records can be safely preserved due to native save/restore
support from guest LBR event.
Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
arch/x86/include/asm/kvm_host.h | 3 +++
arch/x86/kvm/pmu.c | 1 +
arch/x86/kvm/vmx/pmu_intel.c | 9 +++++++++
3 files changed, 13 insertions(+)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 57b281c4b196..dd51250c5688 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -511,6 +511,9 @@ struct kvm_pmu {
* The records may be inaccurate if the host reclaims the LBR.
*/
struct perf_event *lbr_event;
+
+ /* A flag to reduce the overhead of LBR pass-through or cancellation. */
+ bool lbr_already_available;
};
struct kvm_pmu_ops;
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index d0dece055605..583ecb5f5f7c 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -437,6 +437,7 @@ void kvm_pmu_init(struct kvm_vcpu *vcpu)
init_irq_work(&pmu->irq_work, kvm_pmi_trigger_fn);
pmu->event_count = 0;
pmu->need_cleanup = false;
+ pmu->lbr_already_available = false;
kvm_pmu_refresh(vcpu);
}
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index db185dca903d..408d80c9418b 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -316,6 +316,7 @@ static void intel_pmu_free_lbr_event(struct kvm_vcpu *vcpu)
perf_event_release_kernel(event);
intel_pmu_intercept_lbr_msrs(vcpu, true);
+ pmu->lbr_already_available = false;
pmu->event_count--;
pmu->lbr_event = NULL;
}
@@ -653,10 +654,18 @@ static bool intel_pmu_lbr_is_availabile(struct kvm_vcpu *vcpu)
if (!pmu->lbr_event)
return false;
+ if (pmu->lbr_already_available && event_is_oncpu(pmu->lbr_event))
+ return true;
+
+ if (!pmu->lbr_already_available && !event_is_oncpu(pmu->lbr_event))
+ return false;
+
if (event_is_oncpu(pmu->lbr_event)) {
intel_pmu_intercept_lbr_msrs(vcpu, false);
+ pmu->lbr_already_available = true;
} else {
intel_pmu_intercept_lbr_msrs(vcpu, true);
+ pmu->lbr_already_available = false;
return false;
}
--
2.21.3
next prev parent reply other threads:[~2020-05-14 8:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-14 8:30 [PATCH v11 00/11] Guest Last Branch Recording Enabling Like Xu
2020-05-14 8:30 ` [PATCH v11 01/11] perf/x86: Fix variable types for LBR registers Like Xu
2020-05-14 8:30 ` [PATCH v11 02/11] perf/x86/core: Refactor hw->idx checks and cleanup Like Xu
2020-05-14 8:30 ` [PATCH v11 03/11] perf/x86/lbr: Add interface to get basic information about LBR stack Like Xu
2020-05-14 8:30 ` [PATCH v11 04/11] perf/x86: Add constraint to create guest LBR event without hw counter Like Xu
2020-05-18 11:43 ` Peter Zijlstra
2020-05-14 8:30 ` [PATCH v11 05/11] perf/x86: Keep LBR stack unchanged in host context for guest LBR event Like Xu
2020-05-18 11:59 ` Peter Zijlstra
2020-05-18 12:02 ` Peter Zijlstra
2020-05-19 3:08 ` Like Xu
2020-05-19 10:45 ` Peter Zijlstra
2020-05-19 13:25 ` Xu, Like
2020-05-14 8:30 ` [PATCH v11 06/11] KVM: x86/pmu: Tweak kvm_pmu_get_msr to pass 'struct msr_data' in Like Xu
2020-05-14 8:30 ` [PATCH v11 07/11] KVM: x86: Expose MSR_IA32_PERF_CAPABILITIES for LBR record format Like Xu
2020-05-19 10:53 ` Peter Zijlstra
2020-05-19 12:19 ` Xu, Like
2020-05-19 15:12 ` Sean Christopherson
2020-05-14 8:30 ` [PATCH v11 08/11] KVM: x86/pmu: Emulate LBR feature via guest LBR event Like Xu
2020-05-19 11:00 ` Peter Zijlstra
2020-05-19 12:24 ` Xu, Like
2020-05-19 11:01 ` Peter Zijlstra
2020-05-19 12:28 ` Xu, Like
2020-05-19 11:03 ` Peter Zijlstra
2020-05-19 12:40 ` Xu, Like
2020-05-14 8:30 ` [PATCH v11 09/11] KVM: x86/pmu: Release guest LBR event via vPMU lazy release mechanism Like Xu
2020-05-14 8:30 ` [PATCH v11 10/11] KVM: x86/pmu: Check guest LBR availability in case host reclaims them Like Xu
2020-05-19 11:15 ` Peter Zijlstra
2020-05-19 13:10 ` Xu, Like
2020-05-19 14:57 ` Peter Zijlstra
2020-05-20 2:01 ` Xu, Like
2020-05-27 8:17 ` Like Xu
2020-05-14 8:30 ` Like Xu [this message]
2020-05-27 8:28 ` [PATCH v11 00/11] Guest Last Branch Recording Enabling Xu, Like
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