Hi Andrew,
On 01/22/2019 10:49 AM, Andrew Murray wrote:
To prevent re-creating perf events everytime the counter registers
are changed, let's instead lazily create the event when the event
is first enabled and destroy it when it changes.
Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
---
virt/kvm/arm/pmu.c | 114 ++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 78 insertions(+), 36 deletions(-)
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 4464899..1921ca9 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -24,8 +24,11 @@
#include <kvm/arm_pmu.h>
#include <kvm/arm_vgic.h>
-static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 data,
- u64 select_idx);
+static void kvm_pmu_reenable_enabled_single(struct kvm_vcpu *vcpu, u64 pair);
I find the approach good. However the function names are a bit odd and
it makes the code read a bit difficult.
I think we could :
1) Rename the existing
kvm_pmu_{enable/disable}_counter => kvm_pmu_{enable/disable}_[mask or
counters ]
as they operate on a set of counters (as a mask) instead of a single
counter.
And then you may be able to drop "_single" from
kvm_pmu_{enable/disable}_counter"_single() functions below, which makes
better sense for what they do.
+static void kvm_pmu_counter_create_enabled_perf_event(struct kvm_vcpu *vcpu,
+ u64 select_idx);
Could we simply keep kvm_pmu_counter_create_event() and add a comment
above the function explaining that the events are enabled as they are
created lazily ?
+static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc);
+
/**
* kvm_pmu_get_counter_value - get PMU counter value
* @vcpu: The vcpu pointer
@@ -59,18 +62,16 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
*/
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
{
- u64 reg, data;
+ u64 reg;
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+ struct kvm_pmc *pmc = &pmu->pmc[select_idx];
reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx;
__vcpu_sys_reg(vcpu, reg) += (s64)val - kvm_pmu_get_counter_value(vcpu, select_idx);
- reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
- ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;
- data = __vcpu_sys_reg(vcpu, reg + select_idx);
-
- /* Recreate the perf event to reflect the updated sample_period */
- kvm_pmu_create_perf_event(vcpu, data, select_idx);
+ kvm_pmu_stop_counter(vcpu, pmc);
+ kvm_pmu_reenable_enabled_single(vcpu, select_idx);
}
/**
@@ -88,6 +89,7 @@ static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc)
/**
* kvm_pmu_stop_counter - stop PMU counter
+ * @vcpu: The vcpu pointer
* @pmc: The PMU counter pointer
*
* If this counter has been configured to monitor some event, release it here.
@@ -150,6 +152,25 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
}
/**
+ * kvm_pmu_enable_counter_single - create/enable a unpaired counter
+ * @vcpu: The vcpu pointer
+ * @select_idx: The counter index
+ */
+static void kvm_pmu_enable_counter_single(struct kvm_vcpu *vcpu, u64 select_idx)
+{
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+ struct kvm_pmc *pmc = &pmu->pmc[select_idx];
+
+ if (!pmc->perf_event) {
+ kvm_pmu_counter_create_enabled_perf_event(vcpu, select_idx);
+ } else if (pmc->perf_event) {
+ perf_event_enable(pmc->perf_event);
+ if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
+ kvm_debug("fail to enable perf event\n");
nit: failed
+ }
+}
+
+/**
* kvm_pmu_enable_counter - enable selected PMU counter
nit: This is a bit misleading. We could be enabling a set of counters.
Please could we update the comment.
* @vcpu: The vcpu pointer
* @val: the value guest writes to PMCNTENSET register
@@ -159,8 +180,6 @@ u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val)
{
int i;
- struct kvm_pmu *pmu = &vcpu->arch.pmu;
- struct kvm_pmc *pmc;
if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) || !val)
return;
@@ -169,16 +188,44 @@ void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val)
if (!(val & BIT(i)))
continue;
- pmc = &pmu->pmc[i];
- if (pmc->perf_event) {
- perf_event_enable(pmc->perf_event);
- if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
- kvm_debug("fail to enable perf event\n");
- }
+ kvm_pmu_enable_counter_single(vcpu, i);
}
}
/**
+ * kvm_pmu_reenable_enabled_single - reenable a counter if it should be enabled
+ * @vcpu: The vcpu pointer
+ * @select_idx: The counter index
+ */
+static void kvm_pmu_reenable_enabled_single(struct kvm_vcpu *vcpu,
+ u64 select_idx)
+{
+ u64 mask = kvm_pmu_valid_counter_mask(vcpu);
+ u64 set = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & mask;
+
+ if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
+ return;
+
+ if (set & BIT(select_idx))
+ kvm_pmu_enable_counter_single(vcpu, select_idx);
Could we not reuse kvm_pmu_enable_counter() here :
i.e,
static inline void kvm_pmu_reenable_counter(struct kvm_vcpu *vcpu, u64
select_idx)
{
kvm_pmu_enable_counter(vcpu, BIT(select_idx));
}
+}
+
+/**
+ * kvm_pmu_disable_counter - disable selected PMU counter
Stale comment
+ * @vcpu: The vcpu pointer
+ * @pmc: The counter to dissable
nit: s/dissable/disable/
+ */
+static void kvm_pmu_disable_counter_single(struct kvm_vcpu *vcpu,
+ u64 select_idx)
+{
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+ struct kvm_pmc *pmc = &pmu->pmc[select_idx];
+
+ if (pmc->perf_event)
+ perf_event_disable(pmc->perf_event);
+}
+
+/**
* kvm_pmu_disable_counter - disable selected PMU counter
While you are at this, please could you make the comment a bit more
clear. i.e, we disable a set of PMU counters not a single one.
Suzuki
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