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From: Like Xu <like.xu@linux.intel.com>
To: peterz@infradead.org, Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>
Cc: andi@firstfloor.org, kan.liang@linux.intel.com,
	wei.w.wang@intel.com, eranian@google.com,
	liuxiangdong5@huawei.com, Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, Like Xu <like.xu@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>
Subject: [PATCH v5 02/16] perf/x86/intel: Handle guest PEBS overflow PMI for KVM guest
Date: Thu, 15 Apr 2021 11:20:02 +0800
Message-ID: <20210415032016.166201-3-like.xu@linux.intel.com> (raw)
In-Reply-To: <20210415032016.166201-1-like.xu@linux.intel.com>

With PEBS virtualization, the guest PEBS records get delivered to the
guest DS, and the host pmi handler uses perf_guest_cbs->is_in_guest()
to distinguish whether the PMI comes from the guest code like Intel PT.

No matter how many guest PEBS counters are overflowed, only triggering
one fake event is enough. The fake event causes the KVM PMI callback to
be called, thereby injecting the PEBS overflow PMI into the guest.

KVM may inject the PMI with BUFFER_OVF set, even if the guest DS is
empty. That should really be harmless. Thus guest PEBS handler would
retrieve the correct information from its own PEBS records buffer.

Originally-by: Andi Kleen <ak@linux.intel.com>
Co-developed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
 arch/x86/events/intel/core.c | 40 ++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 591d60cc8436..021658df1feb 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2747,6 +2747,43 @@ static void intel_pmu_reset(void)
 	local_irq_restore(flags);
 }
 
+/*
+ * We may be running with guest PEBS events created by KVM, and the
+ * PEBS records are logged into the guest's DS and invisible to host.
+ *
+ * In the case of guest PEBS overflow, we only trigger a fake event
+ * to emulate the PEBS overflow PMI for guest PBES counters in KVM.
+ * The guest will then vm-entry and check the guest DS area to read
+ * the guest PEBS records.
+ *
+ * The contents and other behavior of the guest event do not matter.
+ */
+static void x86_pmu_handle_guest_pebs(struct pt_regs *regs,
+					struct perf_sample_data *data)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	u64 guest_pebs_idxs = cpuc->pebs_enabled & ~cpuc->intel_ctrl_host_mask;
+	struct perf_event *event = NULL;
+	int bit;
+
+	if (!x86_pmu.pebs_active || !guest_pebs_idxs)
+		return;
+
+	for_each_set_bit(bit, (unsigned long *)&guest_pebs_idxs,
+			 INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed) {
+		event = cpuc->events[bit];
+		if (!event->attr.precise_ip)
+			continue;
+
+		perf_sample_data_init(data, 0, event->hw.last_period);
+		if (perf_event_overflow(event, data, regs))
+			x86_pmu_stop(event, 0);
+
+		/* Inject one fake event is enough. */
+		break;
+	}
+}
+
 static int handle_pmi_common(struct pt_regs *regs, u64 status)
 {
 	struct perf_sample_data data;
@@ -2797,6 +2834,9 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 		u64 pebs_enabled = cpuc->pebs_enabled;
 
 		handled++;
+		if (x86_pmu.pebs_vmx && perf_guest_cbs &&
+		    perf_guest_cbs->is_in_guest())
+			x86_pmu_handle_guest_pebs(regs, &data);
 		x86_pmu.drain_pebs(regs, &data);
 		status &= x86_pmu.intel_ctrl | GLOBAL_STATUS_TRACE_TOPAPMI;
 
-- 
2.30.2


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15  3:20 [PATCH v5 00/16] KVM: x86/pmu: Add basic support to enable guest PEBS via DS Like Xu
2021-04-15  3:20 ` [PATCH v5 01/16] perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server Like Xu
2021-04-15  3:20 ` Like Xu [this message]
2021-04-15  3:20 ` [PATCH v5 03/16] perf/x86/core: Pass "struct kvm_pmu *" to determine the guest values Like Xu
2021-04-15  3:20 ` [PATCH v5 04/16] KVM: x86/pmu: Set MSR_IA32_MISC_ENABLE_EMON bit when vPMU is enabled Like Xu
2021-04-15  3:20 ` [PATCH v5 05/16] KVM: x86/pmu: Introduce the ctrl_mask value for fixed counter Like Xu
2021-04-15  3:20 ` [PATCH v5 06/16] KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter Like Xu
2021-04-19  8:11   ` Liuxiangdong
2021-04-19  8:17     ` Xu, Like
2021-04-15  3:20 ` [PATCH v5 07/16] KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS Like Xu
2021-04-15  3:20 ` [PATCH v5 08/16] KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS Like Xu
2021-04-15  3:20 ` [PATCH v5 09/16] KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS Like Xu
2021-04-15  3:20 ` [PATCH v5 10/16] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled Like Xu
2021-04-20  8:30   ` Liuxiangdong
2021-04-20  8:41     ` Xu, Like
2021-04-15  3:20 ` [PATCH v5 11/16] KVM: x86/pmu: Adjust precise_ip to emulate Ice Lake guest PDIR counter Like Xu
2021-04-15  3:20 ` [PATCH v5 12/16] KVM: x86/pmu: Move pmc_speculative_in_use() to arch/x86/kvm/pmu.h Like Xu
2021-04-15  3:20 ` [PATCH v5 13/16] KVM: x86/pmu: Disable guest PEBS temporarily in two rare situations Like Xu
2021-04-15  3:20 ` [PATCH v5 14/16] KVM: x86/pmu: Add kvm_pmu_cap to optimize perf_get_x86_pmu_capability Like Xu
2021-04-15  3:20 ` [PATCH v5 15/16] KVM: x86/cpuid: Refactor host/guest CPU model consistency check Like Xu
2021-04-15  3:20 ` [PATCH v5 16/16] KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64 Like Xu

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