linux-kernel - [PATCH 4/7] KVM: x86/pmu: Avoid perf_event creation for invalid counter config

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Date:   Fri, 12 Nov 2021 17:51:36 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Like Xu <likexu@...cent.com>
Subject: [PATCH 4/7] KVM: x86/pmu: Avoid perf_event creation for invalid counter config

From: Like Xu <likexu@...cent.com>

KVM needs to be fixed to avoid perf_event creation when the requested
hw event on a gp or fixed counter is marked as unavailable in the Intel
guest CPUID 0AH.EBX leaf.

It's proposed to use is_intel_cpuid_event() to distinguish whether the hw
event is an Intel pre-defined architecture event, so that we can decide to
reprogram it with PERF_TYPE_HARDWARE (for fixed and gp) or
PERF_TYPE_RAW (for gp only) perf_event, or just avoid creating perf_event.

If an Intel cpuid event is marked as unavailable by checking
pmu->available_event_types, the intel_find_[fixed|arch]_event() returns
a new special value of "PERF_COUNT_HW_MAX + 1" to tell the caller
to avoid creating perf_ event and not to use PERF_TYPE_RAW mode for gp.

Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/kvm/pmu.c           |  8 +++++++
 arch/x86/kvm/vmx/pmu_intel.c | 45 +++++++++++++++++++++++++++++++-----
 2 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 7093fc70cd38..3b47bd92e7bb 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -111,6 +111,14 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
 		.config = config,
 	};
 
+	/*
+	 * The "config > PERF_COUNT_HW_MAX" only appears when
+	 * the kernel generic event is marked as unavailable
+	 * in the Intel guest architecture event CPUID leaf.
+	 */
+	if (type == PERF_TYPE_HARDWARE && config >= PERF_COUNT_HW_MAX)
+		return;
+
 	attr.sample_period = get_sample_period(pmc, pmc->counter);
 
 	if (in_tx)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 4c04e94ae548..4f58c14efa61 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -68,17 +68,39 @@ static void global_ctrl_changed(struct kvm_pmu *pmu, u64 data)
 		reprogram_counter(pmu, bit);
 }
 
+/* UMask and Event Select Encodings for Intel CPUID Events */
+static inline bool is_intel_cpuid_event(u8 event_select, u8 unit_mask)
+{
+	if ((!unit_mask && event_select == 0x3C) ||
+	    (!unit_mask && event_select == 0xC0) ||
+	    (unit_mask == 0x01 && event_select == 0x3C) ||
+	    (unit_mask == 0x4F && event_select == 0x2E) ||
+	    (unit_mask == 0x41 && event_select == 0x2E) ||
+	    (!unit_mask && event_select == 0xC4) ||
+	    (!unit_mask && event_select == 0xC5))
+		return true;
+
+	/* the unimplemented topdown.slots event check is kipped. */
+	return false;
+}
+
 static unsigned intel_find_arch_event(struct kvm_pmu *pmu,
 				      u8 event_select,
 				      u8 unit_mask)
 {
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(intel_arch_events); i++)
-		if (intel_arch_events[i].eventsel == event_select &&
-		    intel_arch_events[i].unit_mask == unit_mask &&
-		    ((i > 6) || pmu->available_event_types & (1 << i)))
-			break;
+	for (i = 0; i < ARRAY_SIZE(intel_arch_events); i++) {
+		if (intel_arch_events[i].eventsel != event_select ||
+		    intel_arch_events[i].unit_mask != unit_mask)
+			continue;
+
+		if (is_intel_cpuid_event(event_select, unit_mask) &&
+		    !(pmu->available_event_types & BIT_ULL(i)))
+			return PERF_COUNT_HW_MAX + 1;
+
+		break;
+	}
 
 	if (i == ARRAY_SIZE(intel_arch_events))
 		return PERF_COUNT_HW_MAX;
@@ -90,12 +112,23 @@ static unsigned int intel_find_fixed_event(struct kvm_pmu *pmu, int idx)
 {
 	u32 event;
 	size_t size = ARRAY_SIZE(fixed_pmc_events);
+	u8 event_select, unit_mask;
+	unsigned int event_type;
 
 	if (idx >= size)
 		return PERF_COUNT_HW_MAX;
 
 	event = fixed_pmc_events[array_index_nospec(idx, size)];
-	return intel_arch_events[event].event_type;
+
+	event_select = intel_arch_events[event].eventsel;
+	unit_mask = intel_arch_events[event].unit_mask;
+	event_type = intel_arch_events[event].event_type;
+
+	if (is_intel_cpuid_event(event_select, unit_mask) &&
+	    !(pmu->available_event_types & BIT_ULL(event_type)))
+		return PERF_COUNT_HW_MAX + 1;
+
+	return event_type;
 }
 
 /* check if a PMC is enabled by comparing it with globl_ctrl bits. */
-- 
2.33.0