Commit 7ff775ac authored by Jim Mattson's avatar Jim Mattson Committed by Paolo Bonzini
Browse files

KVM: x86/pmu: Use binary search to check filtered events 



The PMU event filter may contain up to 300 events. Replace the linear
search in reprogram_gp_counter() with a binary search.

Signed-off-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220115052431.447232-2-jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1a1d1dbc

arch/x86/kvm/pmu.c

+19 −11
Original line number Diff line number Diff line
@@ -13,6 +13,8 @@ 
#include <linux/types.h>

#include <linux/kvm_host.h>

#include <linux/perf_event.h>

#include <linux/bsearch.h>

#include <linux/sort.h>

#include <asm/perf_event.h>

#include "x86.h"

#include "cpuid.h"
@@ -172,12 +174,16 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc) 
	return true;

}



static int cmp_u64(const void *a, const void *b)

{

	return *(__u64 *)a - *(__u64 *)b;

}



void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)

{

	unsigned config, type = PERF_TYPE_RAW;

	struct kvm *kvm = pmc->vcpu->kvm;

	struct kvm_pmu_event_filter *filter;

	int i;

	bool allow_event = true;



	if (eventsel & ARCH_PERFMON_EVENTSEL_PIN_CONTROL)
@@ -192,16 +198,13 @@ void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel) 


	filter = srcu_dereference(kvm->arch.pmu_event_filter, &kvm->srcu);

	if (filter) {

		for (i = 0; i < filter->nevents; i++)

			if (filter->events[i] ==

			    (eventsel & AMD64_RAW_EVENT_MASK_NB))

				break;

		if (filter->action == KVM_PMU_EVENT_ALLOW &&

		    i == filter->nevents)

			allow_event = false;

		if (filter->action == KVM_PMU_EVENT_DENY &&

		    i < filter->nevents)

			allow_event = false;

		__u64 key = eventsel & AMD64_RAW_EVENT_MASK_NB;



		if (bsearch(&key, filter->events, filter->nevents,

			    sizeof(__u64), cmp_u64))

			allow_event = filter->action == KVM_PMU_EVENT_ALLOW;

		else

			allow_event = filter->action == KVM_PMU_EVENT_DENY;

	}

	if (!allow_event)

		return;
@@ -576,6 +579,11 @@ int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp) 
	/* Ensure nevents can't be changed between the user copies. */

	*filter = tmp;



	/*

	 * Sort the in-kernel list so that we can search it with bsearch.

	 */

	sort(&filter->events, filter->nevents, sizeof(__u64), cmp_u64, NULL);



	mutex_lock(&kvm->lock);

	filter = rcu_replace_pointer(kvm->arch.pmu_event_filter, filter,

				     mutex_is_locked(&kvm->lock));