[PATCH 1/5] KVM: x86/pmu: Emulate CTR overflow directly in kvm_pmu_handle_event()

Like Xu
2023-03-10T10:54:35Z

From: Like Xu <likexu@tencent.com>

More and more vPMU emulations are deferred to kvm_pmu_handle_event()
as it reduces the overhead of repeated execution. The reprogram_counter()
is only responsible for creating the required perf_event, and naturally
doesn't include the counter overflow part from emulated instruction events.

Prior to this change, the assignment of pmc->prev_counter always occurred
after pmc was enabled, and to keep the same semantics, pmc->prev_counter
always needed to be reset after it has taken effect.

No functional change intended.

Signed-off-by: Like Xu <likexu@tencent.com>
---
arch/x86/kvm/pmu.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index a1a79b5f49d7..d1c89a6625a0 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -418,9 +418,6 @@ static void reprogram_counter(struct kvm_pmc *pmc)
if (!event_is_allowed(pmc))
goto reprogram_complete;

- if (pmc->counter < pmc->prev_counter)
- __kvm_perf_overflow(pmc, false);
-
if (eventsel & ARCH_PERFMON_EVENTSEL_PIN_CONTROL)
printk_once("kvm pmu: pin control bit is ignored\n");

@@ -458,6 +455,13 @@ static void reprogram_counter(struct kvm_pmc *pmc)

reprogram_complete:
clear_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->reprogram_pmi);
+}
+
+static inline void kvm_pmu_handle_pmc_overflow(struct kvm_pmc *pmc)
+{
+ if (pmc->counter < pmc->prev_counter)
+ __kvm_perf_overflow(pmc, false);
+
pmc->prev_counter = 0;
}

@@ -475,6 +479,7 @@ void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
}

reprogram_counter(pmc);
+ kvm_pmu_handle_pmc_overflow(pmc);
}

/*
--
2.39.2