[PATCH 5.10 505/545] KVM: x86/pmu: Use binary search to check filtered events

Greg Kroah-Hartman
2022-08-19T16:49:28Z

From: Jim Mattson <jmattson@google.com>

[ Upstream commit 7ff775aca48adc854436b92c060e5eebfffb6a4a ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/pmu.c | 30 +++++++++++++++++++-----------
1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 2f83b5d948b3..350e7cdaad02 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -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"
@@ -168,13 +170,17 @@ 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)
{
u64 config;
u32 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)
@@ -189,16 +195,13 @@ 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;
@@ -507,6 +510,11 @@ 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));
--
2.35.1