KVM: x86: Add fixed counters to PMU filter

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

Signed-off-by: Eric Hankland <[e-mail]>
[No need to check padding fields for zero. - Paolo]
Signed-off-by: Paolo Bonzini <[e-mail]>

Documentation/virtual/kvm/api.txt

···
 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.
+
+No flags are defined yet, the field must be zero.
 
 Valid values for 'action':
 #define KVM_PMU_EVENT_ALLOW 0

arch/x86/include/uapi/asm/kvm.h

···
 
 /* 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

arch/x86/kvm/pmu.c

···
 #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";
···
 {
 	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),
···
 	    tmp.action != KVM_PMU_EVENT_DENY)
 		return -EINVAL;
 
+	if (tmp.flags != 0)
+		return -EINVAL;
+
 	if (tmp.nevents > KVM_PMU_EVENT_FILTER_MAX_EVENTS)
 		return -E2BIG;
 
···
 	mutex_unlock(&kvm->lock);
 
 	synchronize_srcu_expedited(&kvm->srcu);
- 	r = 0;
+	r = 0;
 cleanup:
 	kfree(filter);
- 	return r;
+	return r;
 }