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

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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: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220115052431.447232-2-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Jim Mattson 2022-01-14 21:24:26 -08:00 committed by Paolo Bonzini
parent 1a1d1dbce6
commit 7ff775aca4
1 changed files with 19 additions and 11 deletions
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30
arch/x86/kvm/pmu.c
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@ -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));