linux-kernel - [PATCH] KVM: x86: Add fixed counters to PMU filter

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Message-Id: <20190718183818.190051-1-ehankland@google.com>
Date:   Thu, 18 Jul 2019 11:38:18 -0700
From:   Eric Hankland <ehankland@...gle.com>
To:     Wei Wang <wei.w.wang@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>,
        ehankland <ehankland@...gle.com>
Subject: [PATCH] KVM: x86: Add fixed counters to PMU filter

From: ehankland <ehankland@...gle.com>

Updates KVM_CAP_PMU_EVENT_FILTER so it can also whitelist or blacklist
fixed counters.

Signed-off-by: ehankland <ehankland@...gle.com>
---
 Documentation/virtual/kvm/api.txt | 13 ++++++++-----
 arch/x86/include/uapi/asm/kvm.h   |  9 ++++++---
 arch/x86/kvm/pmu.c                | 30 +++++++++++++++++++++++++-----
 3 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 2cd6250b2896..96bcf1aa1931 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4090,17 +4090,20 @@ Parameters: struct kvm_pmu_event_filter (in)
 Returns: 0 on success, -1 on error
 
 struct kvm_pmu_event_filter {
-       __u32 action;
-       __u32 nevents;
-       __u64 events[0];
+	__u32 action;
+	__u32 nevents;
+	__u32 fixed_counter_bitmap;
+	__u32 flags;
+	__u32 pad[4];
+	__u64 events[0];
 };
 
 This ioctl restricts the set of PMU events that the guest can program.
 The argument holds a list of events which will be allowed or denied.
 The eventsel+umask of each event the guest attempts to program is compared
 against the events field to determine whether the guest should have access.
-This only affects general purpose counters; fixed purpose counters can
-be disabled by changing the perfmon CPUID leaf.
+The events field only controls general purpose counters; fixed purpose
+counters are controlled by the fixed_counter_bitmap.
 
 Valid values for 'action':
 #define KVM_PMU_EVENT_ALLOW 0
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index e901b0ab116f..503d3f42da16 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -435,9 +435,12 @@ struct kvm_nested_state {
 
 /* for KVM_CAP_PMU_EVENT_FILTER */
 struct kvm_pmu_event_filter {
-       __u32 action;
-       __u32 nevents;
-       __u64 events[0];
+	__u32 action;
+	__u32 nevents;
+	__u32 fixed_counter_bitmap;
+	__u32 flags;
+	__u32 pad[4];
+	__u64 events[0];
 };
 
 #define KVM_PMU_EVENT_ALLOW 0
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index aa5a2597305a..ae5cd1b02086 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -19,8 +19,8 @@
 #include "lapic.h"
 #include "pmu.h"
 
-/* This keeps the total size of the filter under 4k. */
-#define KVM_PMU_EVENT_FILTER_MAX_EVENTS 63
+/* This is enough to filter the vast majority of currently defined events. */
+#define KVM_PMU_EVENT_FILTER_MAX_EVENTS 300
 
 /* NOTE:
  * - Each perf counter is defined as "struct kvm_pmc";
@@ -206,12 +206,25 @@ void reprogram_fixed_counter(struct kvm_pmc *pmc, u8 ctrl, int idx)
 {
 	unsigned en_field = ctrl & 0x3;
 	bool pmi = ctrl & 0x8;
+	struct kvm_pmu_event_filter *filter;
+	struct kvm *kvm = pmc->vcpu->kvm;
+
 
 	pmc_stop_counter(pmc);
 
 	if (!en_field || !pmc_is_enabled(pmc))
 		return;
 
+	filter = srcu_dereference(kvm->arch.pmu_event_filter, &kvm->srcu);
+	if (filter) {
+		if (filter->action == KVM_PMU_EVENT_DENY &&
+		    test_bit(idx, (ulong *)&filter->fixed_counter_bitmap))
+			return;
+		if (filter->action == KVM_PMU_EVENT_ALLOW &&
+		    !test_bit(idx, (ulong *)&filter->fixed_counter_bitmap))
+			return;
+	}
+
 	pmc_reprogram_counter(pmc, PERF_TYPE_HARDWARE,
 			      kvm_x86_ops->pmu_ops->find_fixed_event(idx),
 			      !(en_field & 0x2), /* exclude user */
@@ -376,7 +389,7 @@ int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_pmu_event_filter tmp, *filter;
 	size_t size;
-	int r;
+	int r, i;
 
 	if (copy_from_user(&tmp, argp, sizeof(tmp)))
 		return -EFAULT;
@@ -385,6 +398,13 @@ int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp)
 	    tmp.action != KVM_PMU_EVENT_DENY)
 		return -EINVAL;
 
+	if (tmp.flags != 0)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(tmp.pad); i++)
+		if (tmp.pad[i] != 0)
+			return -EINVAL;
+
 	if (tmp.nevents > KVM_PMU_EVENT_FILTER_MAX_EVENTS)
 		return -E2BIG;
 
@@ -406,8 +426,8 @@ int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp)
 	mutex_unlock(&kvm->lock);
 
 	synchronize_srcu_expedited(&kvm->srcu);
- 	r = 0;
+	r = 0;
 cleanup:
 	kfree(filter);
- 	return r;
+	return r;
 }