linux/arch/arm64/kvm/pmu-emul.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2015 Linaro Ltd.
 * Author: Shannon Zhao <shannon.zhao@linaro.org>
 */

#include <linux/cpu.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/perf_event.h>
#include <linux/perf/arm_pmu.h>
#include <linux/uaccess.h>
#include <asm/kvm_emulate.h>
#include <kvm/arm_pmu.h>
#include <kvm/arm_vgic.h>

static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx);
static void kvm_pmu_update_pmc_chained(struct kvm_vcpu *vcpu, u64 select_idx);
static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc);

#define PERF_ATTR_CFG1_KVM_PMU_CHAINED 0x1

static u32 kvm_pmu_event_mask(struct kvm *kvm)
{
	switch (kvm->arch.pmuver) {
	case 1:			/* ARMv8.0 */
		return GENMASK(9, 0);
	case 4:			/* ARMv8.1 */
	case 5:			/* ARMv8.4 */
	case 6:			/* ARMv8.5 */
		return GENMASK(15, 0);
	default:		/* Shouldn't be here, just for sanity */
		WARN_ONCE(1, "Unknown PMU version %d\n", kvm->arch.pmuver);
		return 0;
	}
}

/**
 * kvm_pmu_idx_is_64bit - determine if select_idx is a 64bit counter
 * @vcpu: The vcpu pointer
 * @select_idx: The counter index
 */
static bool kvm_pmu_idx_is_64bit(struct kvm_vcpu *vcpu, u64 select_idx)
{
	return (select_idx == ARMV8_PMU_CYCLE_IDX &&
		__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_LC);
}

static struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
{
	struct kvm_pmu *pmu;
	struct kvm_vcpu_arch *vcpu_arch;

	pmc -= pmc->idx;
	pmu = container_of(pmc, struct kvm_pmu, pmc[0]);
	vcpu_arch = container_of(pmu, struct kvm_vcpu_arch, pmu);
	return container_of(vcpu_arch, struct kvm_vcpu, arch);
}

/**
 * kvm_pmu_pmc_is_chained - determine if the pmc is chained
 * @pmc: The PMU counter pointer
 */
static bool kvm_pmu_pmc_is_chained(struct kvm_pmc *pmc)
{
	struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc);

	return test_bit(pmc->idx >> 1, vcpu->arch.pmu.chained);
}

/**
 * kvm_pmu_idx_is_high_counter - determine if select_idx is a high/low counter
 * @select_idx: The counter index
 */
static bool kvm_pmu_idx_is_high_counter(u64 select_idx)
{
	return select_idx & 0x1;
}

/**
 * kvm_pmu_get_canonical_pmc - obtain the canonical pmc
 * @pmc: The PMU counter pointer
 *
 * When a pair of PMCs are chained together we use the low counter (canonical)
 * to hold the underlying perf event.
 */
static struct kvm_pmc *kvm_pmu_get_canonical_pmc(struct kvm_pmc *pmc)
{
	if (kvm_pmu_pmc_is_chained(pmc) &&
	    kvm_pmu_idx_is_high_counter(pmc->idx))
		return pmc - 1;

	return pmc;
}
static struct kvm_pmc *kvm_pmu_get_alternate_pmc(struct kvm_pmc *pmc)
{
	if (kvm_pmu_idx_is_high_counter(pmc->idx))
		return pmc - 1;
	else
		return pmc + 1;
}

/**
 * kvm_pmu_idx_has_chain_evtype - determine if the event type is chain
 * @vcpu: The vcpu pointer
 * @select_idx: The counter index
 */
static bool kvm_pmu_idx_has_chain_evtype(struct kvm_vcpu *vcpu, u64 select_idx)
{
	u64 eventsel, reg;

	select_idx |= 0x1;

	if (select_idx == ARMV8_PMU_CYCLE_IDX)
		return false;

	reg = PMEVTYPER0_EL0 + select_idx;
	eventsel = __vcpu_sys_reg(vcpu, reg) & kvm_pmu_event_mask(vcpu->kvm);

	return eventsel == ARMV8_PMUV3_PERFCTR_CHAIN;
}

/**
 * kvm_pmu_get_pair_counter_value - get PMU counter value
 * @vcpu: The vcpu pointer
 * @pmc: The PMU counter pointer
 */
static u64 kvm_pmu_get_pair_counter_value(struct kvm_vcpu *vcpu,
					  struct kvm_pmc *pmc)
{
	u64 counter, counter_high, reg, enabled, running;

	if (kvm_pmu_pmc_is_chained(pmc)) {
		pmc = kvm_pmu_get_canonical_pmc(pmc);
		reg = PMEVCNTR0_EL0 + pmc->idx;

		counter = __vcpu_sys_reg(vcpu, reg);
		counter_high = __vcpu_sys_reg(vcpu, reg + 1);

		counter = lower_32_bits(counter) | (counter_high << 32);
	} else {
		reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
		      ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
		counter = __vcpu_sys_reg(vcpu, reg);
	}

	/*
	 * The real counter value is equal to the value of counter register plus
	 * the value perf event counts.
	 */
	if (pmc->perf_event)
		counter += perf_event_read_value(pmc->perf_event, &enabled,
						 &running);

	return counter;
}

/**
 * kvm_pmu_get_counter_value - get PMU counter value
 * @vcpu: The vcpu pointer
 * @select_idx: The counter index
 */
u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
{
	u64 counter;
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_pmc *pmc = &pmu->pmc[select_idx];

	counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);

	if (kvm_pmu_pmc_is_chained(pmc) &&
	    kvm_pmu_idx_is_high_counter(select_idx))
		counter = upper_32_bits(counter);
	else if (select_idx != ARMV8_PMU_CYCLE_IDX)
		counter = lower_32_bits(counter);

	return counter;
}

/**
 * kvm_pmu_set_counter_value - set PMU counter value
 * @vcpu: The vcpu pointer
 * @select_idx: The counter index
 * @val: The counter value
 */
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
{
	u64 reg;

	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);

	/* Recreate the perf event to reflect the updated sample_period */
	kvm_pmu_create_perf_event(vcpu, select_idx);
}

/**
 * kvm_pmu_release_perf_event - remove the perf event
 * @pmc: The PMU counter pointer
 */
static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc)
{
	pmc = kvm_pmu_get_canonical_pmc(pmc);
	if (pmc->perf_event) {
		perf_event_disable(pmc->perf_event);
		perf_event_release_kernel(pmc->perf_event);
		pmc->perf_event = NULL;
	}
}

/**
 * kvm_pmu_stop_counter - stop PMU counter
 * @pmc: The PMU counter pointer
 *
 * If this counter has been configured to monitor some event, release it here.
 */
static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
{
	u64 counter, reg, val;

	pmc = kvm_pmu_get_canonical_pmc(pmc);
	if (!pmc->perf_event)
		return;

	counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);

	if (pmc->idx == ARMV8_PMU_CYCLE_IDX) {
		reg = PMCCNTR_EL0;
		val = counter;
	} else {
		reg = PMEVCNTR0_EL0 + pmc->idx;
		val = lower_32_bits(counter);
	}

	__vcpu_sys_reg(vcpu, reg) = val;

	if (kvm_pmu_pmc_is_chained(pmc))
		__vcpu_sys_reg(vcpu, reg + 1) = upper_32_bits(counter);

	kvm_pmu_release_perf_event(pmc);
}

/**
 * kvm_pmu_vcpu_init - assign pmu counter idx for cpu
 * @vcpu: The vcpu pointer
 *
 */
void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu)
{
	int i;
	struct kvm_pmu *pmu = &vcpu->arch.pmu;

	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
		pmu->pmc[i].idx = i;
}

/**
 * kvm_pmu_vcpu_reset - reset pmu state for cpu
 * @vcpu: The vcpu pointer
 *
 */
void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu)
{
	unsigned long mask = kvm_pmu_valid_counter_mask(vcpu);
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	int i;

	for_each_set_bit(i, &mask, 32)
		kvm_pmu_stop_counter(vcpu, &pmu->pmc[i]);

	bitmap_zero(vcpu->arch.pmu.chained, ARMV8_PMU_MAX_COUNTER_PAIRS);
}

/**
 * kvm_pmu_vcpu_destroy - free perf event of PMU for cpu
 * @vcpu: The vcpu pointer
 *
 */
void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu)
{
	int i;
	struct kvm_pmu *pmu = &vcpu->arch.pmu;

	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++)
		kvm_pmu_release_perf_event(&pmu->pmc[i]);
}

u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
{
	u64 val = __vcpu_sys_reg(vcpu, PMCR_EL0) >> ARMV8_PMU_PMCR_N_SHIFT;

	val &= ARMV8_PMU_PMCR_N_MASK;
	if (val == 0)
		return BIT(ARMV8_PMU_CYCLE_IDX);
	else
		return GENMASK(val - 1, 0) | BIT(ARMV8_PMU_CYCLE_IDX);
}

/**
 * kvm_pmu_enable_counter_mask - enable selected PMU counters
 * @vcpu: The vcpu pointer
 * @val: the value guest writes to PMCNTENSET register
 *
 * Call perf_event_enable to start counting the perf event
 */
void kvm_pmu_enable_counter_mask(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;

	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
		if (!(val & BIT(i)))
			continue;

		pmc = &pmu->pmc[i];

		/* A change in the enable state may affect the chain state */
		kvm_pmu_update_pmc_chained(vcpu, i);
		kvm_pmu_create_perf_event(vcpu, i);

		/* At this point, pmc must be the canonical */
		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_disable_counter_mask - disable selected PMU counters
 * @vcpu: The vcpu pointer
 * @val: the value guest writes to PMCNTENCLR register
 *
 * Call perf_event_disable to stop counting the perf event
 */
void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
{
	int i;
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_pmc *pmc;

	if (!val)
		return;

	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
		if (!(val & BIT(i)))
			continue;

		pmc = &pmu->pmc[i];

		/* A change in the enable state may affect the chain state */
		kvm_pmu_update_pmc_chained(vcpu, i);
		kvm_pmu_create_perf_event(vcpu, i);

		/* At this point, pmc must be the canonical */
		if (pmc->perf_event)
			perf_event_disable(pmc->perf_event);
	}
}

static u64 kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
{
	u64 reg = 0;

	if ((__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E)) {
		reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
		reg &= __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
		reg &= __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
		reg &= kvm_pmu_valid_counter_mask(vcpu);
	}

	return reg;
}

static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	bool overflow;

	if (!kvm_arm_pmu_v3_ready(vcpu))
		return;

	overflow = !!kvm_pmu_overflow_status(vcpu);
	if (pmu->irq_level == overflow)
		return;

	pmu->irq_level = overflow;

	if (likely(irqchip_in_kernel(vcpu->kvm))) {
		int ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
					      pmu->irq_num, overflow, pmu);
		WARN_ON(ret);
	}
}

bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_sync_regs *sregs = &vcpu->run->s.regs;
	bool run_level = sregs->device_irq_level & KVM_ARM_DEV_PMU;

	if (likely(irqchip_in_kernel(vcpu->kvm)))
		return false;

	return pmu->irq_level != run_level;
}

/*
 * Reflect the PMU overflow interrupt output level into the kvm_run structure
 */
void kvm_pmu_update_run(struct kvm_vcpu *vcpu)
{
	struct kvm_sync_regs *regs = &vcpu->run->s.regs;

	/* Populate the timer bitmap for user space */
	regs->device_irq_level &= ~KVM_ARM_DEV_PMU;
	if (vcpu->arch.pmu.irq_level)
		regs->device_irq_level |= KVM_ARM_DEV_PMU;
}

/**
 * kvm_pmu_flush_hwstate - flush pmu state to cpu
 * @vcpu: The vcpu pointer
 *
 * Check if the PMU has overflowed while we were running in the host, and inject
 * an interrupt if that was the case.
 */
void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu)
{
	kvm_pmu_update_state(vcpu);
}

/**
 * kvm_pmu_sync_hwstate - sync pmu state from cpu
 * @vcpu: The vcpu pointer
 *
 * Check if the PMU has overflowed while we were running in the guest, and
 * inject an interrupt if that was the case.
 */
void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu)
{
	kvm_pmu_update_state(vcpu);
}

/**
 * When the perf event overflows, set the overflow status and inform the vcpu.
 */
static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
				  struct perf_sample_data *data,
				  struct pt_regs *regs)
{
	struct kvm_pmc *pmc = perf_event->overflow_handler_context;
	struct arm_pmu *cpu_pmu = to_arm_pmu(perf_event->pmu);
	struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc);
	int idx = pmc->idx;
	u64 period;

	cpu_pmu->pmu.stop(perf_event, PERF_EF_UPDATE);

	/*
	 * Reset the sample period to the architectural limit,
	 * i.e. the point where the counter overflows.
	 */
	period = -(local64_read(&perf_event->count));

	if (!kvm_pmu_idx_is_64bit(vcpu, pmc->idx))
		period &= GENMASK(31, 0);

	local64_set(&perf_event->hw.period_left, 0);
	perf_event->attr.sample_period = period;
	perf_event->hw.sample_period = period;

	__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx);

	if (kvm_pmu_overflow_status(vcpu)) {
		kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
		kvm_vcpu_kick(vcpu);
	}

	cpu_pmu->pmu.start(perf_event, PERF_EF_RELOAD);
}

/**
 * kvm_pmu_software_increment - do software increment
 * @vcpu: The vcpu pointer
 * @val: the value guest writes to PMSWINC register
 */
void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	int i;

	if (!(__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E))
		return;

	/* Weed out disabled counters */
	val &= __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);

	for (i = 0; i < ARMV8_PMU_CYCLE_IDX; i++) {
		u64 type, reg;

		if (!(val & BIT(i)))
			continue;

		/* PMSWINC only applies to ... SW_INC! */
		type = __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + i);
		type &= kvm_pmu_event_mask(vcpu->kvm);
		if (type != ARMV8_PMUV3_PERFCTR_SW_INCR)
			continue;

		/* increment this even SW_INC counter */
		reg = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) + 1;
		reg = lower_32_bits(reg);
		__vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i) = reg;

		if (reg) /* no overflow on the low part */
			continue;

		if (kvm_pmu_pmc_is_chained(&pmu->pmc[i])) {
			/* increment the high counter */
			reg = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i + 1) + 1;
			reg = lower_32_bits(reg);
			__vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i + 1) = reg;
			if (!reg) /* mark overflow on the high counter */
				__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i + 1);
		} else {
			/* mark overflow on low counter */
			__vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(i);
		}
	}
}

/**
 * kvm_pmu_handle_pmcr - handle PMCR register
 * @vcpu: The vcpu pointer
 * @val: the value guest writes to PMCR register
 */
void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
{
	unsigned long mask = kvm_pmu_valid_counter_mask(vcpu);
	int i;

	if (val & ARMV8_PMU_PMCR_E) {
		kvm_pmu_enable_counter_mask(vcpu,
		       __vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & mask);
	} else {
		kvm_pmu_disable_counter_mask(vcpu, mask);
	}

	if (val & ARMV8_PMU_PMCR_C)
		kvm_pmu_set_counter_value(vcpu, ARMV8_PMU_CYCLE_IDX, 0);

	if (val & ARMV8_PMU_PMCR_P) {
		for_each_set_bit(i, &mask, 32)
			kvm_pmu_set_counter_value(vcpu, i, 0);
	}
}

static bool kvm_pmu_counter_is_enabled(struct kvm_vcpu *vcpu, u64 select_idx)
{
	return (__vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) &&
	       (__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & BIT(select_idx));
}

/**
 * kvm_pmu_create_perf_event - create a perf event for a counter
 * @vcpu: The vcpu pointer
 * @select_idx: The number of selected counter
 */
static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_pmc *pmc;
	struct perf_event *event;
	struct perf_event_attr attr;
	u64 eventsel, counter, reg, data;

	/*
	 * For chained counters the event type and filtering attributes are
	 * obtained from the low/even counter. We also use this counter to
	 * determine if the event is enabled/disabled.
	 */
	pmc = kvm_pmu_get_canonical_pmc(&pmu->pmc[select_idx]);

	reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
	      ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + pmc->idx;
	data = __vcpu_sys_reg(vcpu, reg);

	kvm_pmu_stop_counter(vcpu, pmc);
	if (pmc->idx == ARMV8_PMU_CYCLE_IDX)
		eventsel = ARMV8_PMUV3_PERFCTR_CPU_CYCLES;
	else
		eventsel = data & kvm_pmu_event_mask(vcpu->kvm);

	/* Software increment event doesn't need to be backed by a perf event */
	if (eventsel == ARMV8_PMUV3_PERFCTR_SW_INCR)
		return;

	/*
	 * If we have a filter in place and that the event isn't allowed, do
	 * not install a perf event either.
	 */
	if (vcpu->kvm->arch.pmu_filter &&
	    !test_bit(eventsel, vcpu->kvm->arch.pmu_filter))
		return;

	memset(&attr, 0, sizeof(struct perf_event_attr));
	attr.type = PERF_TYPE_RAW;
	attr.size = sizeof(attr);
	attr.pinned = 1;
	attr.disabled = !kvm_pmu_counter_is_enabled(vcpu, pmc->idx);
	attr.exclude_user = data & ARMV8_PMU_EXCLUDE_EL0 ? 1 : 0;
	attr.exclude_kernel = data & ARMV8_PMU_EXCLUDE_EL1 ? 1 : 0;
	attr.exclude_hv = 1; /* Don't count EL2 events */
	attr.exclude_host = 1; /* Don't count host events */
	attr.config = eventsel;

	counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);

	if (kvm_pmu_pmc_is_chained(pmc)) {
		/**
		 * The initial sample period (overflow count) of an event. For
		 * chained counters we only support overflow interrupts on the
		 * high counter.
		 */
		attr.sample_period = (-counter) & GENMASK(63, 0);
		attr.config1 |= PERF_ATTR_CFG1_KVM_PMU_CHAINED;

		event = perf_event_create_kernel_counter(&attr, -1, current,
							 kvm_pmu_perf_overflow,
							 pmc + 1);
	} else {
		/* The initial sample period (overflow count) of an event. */
		if (kvm_pmu_idx_is_64bit(vcpu, pmc->idx))
			attr.sample_period = (-counter) & GENMASK(63, 0);
		else
			attr.sample_period = (-counter) & GENMASK(31, 0);

		event = perf_event_create_kernel_counter(&attr, -1, current,
						 kvm_pmu_perf_overflow, pmc);
	}

	if (IS_ERR(event)) {
		pr_err_once("kvm: pmu event creation failed %ld\n",
			    PTR_ERR(event));
		return;
	}

	pmc->perf_event = event;
}

/**
 * kvm_pmu_update_pmc_chained - update chained bitmap
 * @vcpu: The vcpu pointer
 * @select_idx: The number of selected counter
 *
 * Update the chained bitmap based on the event type written in the
 * typer register and the enable state of the odd register.
 */
static void kvm_pmu_update_pmc_chained(struct kvm_vcpu *vcpu, u64 select_idx)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_pmc *pmc = &pmu->pmc[select_idx], *canonical_pmc;
	bool new_state, old_state;

	old_state = kvm_pmu_pmc_is_chained(pmc);
	new_state = kvm_pmu_idx_has_chain_evtype(vcpu, pmc->idx) &&
		    kvm_pmu_counter_is_enabled(vcpu, pmc->idx | 0x1);

	if (old_state == new_state)
		return;

	canonical_pmc = kvm_pmu_get_canonical_pmc(pmc);
	kvm_pmu_stop_counter(vcpu, canonical_pmc);
	if (new_state) {
		/*
		 * During promotion from !chained to chained we must ensure
		 * the adjacent counter is stopped and its event destroyed
		 */
		kvm_pmu_stop_counter(vcpu, kvm_pmu_get_alternate_pmc(pmc));
		set_bit(pmc->idx >> 1, vcpu->arch.pmu.chained);
		return;
	}
	clear_bit(pmc->idx >> 1, vcpu->arch.pmu.chained);
}

/**
 * kvm_pmu_set_counter_event_type - set selected counter to monitor some event
 * @vcpu: The vcpu pointer
 * @data: The data guest writes to PMXEVTYPER_EL0
 * @select_idx: The number of selected counter
 *
 * When OS accesses PMXEVTYPER_EL0, that means it wants to set a PMC to count an
 * event with given hardware event number. Here we call perf_event API to
 * emulate this action and create a kernel perf event for it.
 */
void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
				    u64 select_idx)
{
	u64 reg, mask;

	mask  =  ARMV8_PMU_EVTYPE_MASK;
	mask &= ~ARMV8_PMU_EVTYPE_EVENT;
	mask |= kvm_pmu_event_mask(vcpu->kvm);

	reg = (select_idx == ARMV8_PMU_CYCLE_IDX)
	      ? PMCCFILTR_EL0 : PMEVTYPER0_EL0 + select_idx;

	__vcpu_sys_reg(vcpu, reg) = data & mask;

	kvm_pmu_update_pmc_chained(vcpu, select_idx);
	kvm_pmu_create_perf_event(vcpu, select_idx);
}

static int kvm_pmu_probe_pmuver(void)
{
	struct perf_event_attr attr = { };
	struct perf_event *event;
	struct arm_pmu *pmu;
	int pmuver = 0xf;

	/*
	 * Create a dummy event that only counts user cycles. As we'll never
	 * leave this function with the event being live, it will never
	 * count anything. But it allows us to probe some of the PMU
	 * details. Yes, this is terrible.
	 */
	attr.type = PERF_TYPE_RAW;
	attr.size = sizeof(attr);
	attr.pinned = 1;
	attr.disabled = 0;
	attr.exclude_user = 0;
	attr.exclude_kernel = 1;
	attr.exclude_hv = 1;
	attr.exclude_host = 1;
	attr.config = ARMV8_PMUV3_PERFCTR_CPU_CYCLES;
	attr.sample_period = GENMASK(63, 0);

	event = perf_event_create_kernel_counter(&attr, -1, current,
						 kvm_pmu_perf_overflow, &attr);

	if (IS_ERR(event)) {
		pr_err_once("kvm: pmu event creation failed %ld\n",
			    PTR_ERR(event));
		return 0xf;
	}

	if (event->pmu) {
		pmu = to_arm_pmu(event->pmu);
		if (pmu->pmuver)
			pmuver = pmu->pmuver;
	}

	perf_event_disable(event);
	perf_event_release_kernel(event);

	return pmuver;
}

bool kvm_arm_support_pmu_v3(void)
{
	/*
	 * Check if HW_PERF_EVENTS are supported by checking the number of
	 * hardware performance counters. This could ensure the presence of
	 * a physical PMU and CONFIG_PERF_EVENT is selected.
	 */
	return (perf_num_counters() > 0);
}

int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu)
{
	if (!vcpu->arch.pmu.created)
		return 0;

	/*
	 * A valid interrupt configuration for the PMU is either to have a
	 * properly configured interrupt number and using an in-kernel
	 * irqchip, or to not have an in-kernel GIC and not set an IRQ.
	 */
	if (irqchip_in_kernel(vcpu->kvm)) {
		int irq = vcpu->arch.pmu.irq_num;
		if (!kvm_arm_pmu_irq_initialized(vcpu))
			return -EINVAL;

		/*
		 * If we are using an in-kernel vgic, at this point we know
		 * the vgic will be initialized, so we can check the PMU irq
		 * number against the dimensions of the vgic and make sure
		 * it's valid.
		 */
		if (!irq_is_ppi(irq) && !vgic_valid_spi(vcpu->kvm, irq))
			return -EINVAL;
	} else if (kvm_arm_pmu_irq_initialized(vcpu)) {
		   return -EINVAL;
	}

	kvm_pmu_vcpu_reset(vcpu);
	vcpu->arch.pmu.ready = true;

	return 0;
}

static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
{
	if (irqchip_in_kernel(vcpu->kvm)) {
		int ret;

		/*
		 * If using the PMU with an in-kernel virtual GIC
		 * implementation, we require the GIC to be already
		 * initialized when initializing the PMU.
		 */
		if (!vgic_initialized(vcpu->kvm))
			return -ENODEV;

		if (!kvm_arm_pmu_irq_initialized(vcpu))
			return -ENXIO;

		ret = kvm_vgic_set_owner(vcpu, vcpu->arch.pmu.irq_num,
					 &vcpu->arch.pmu);
		if (ret)
			return ret;
	}

	vcpu->arch.pmu.created = true;
	return 0;
}

/*
 * For one VM the interrupt type must be same for each vcpu.
 * As a PPI, the interrupt number is the same for all vcpus,
 * while as an SPI it must be a separate number per vcpu.
 */
static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
{
	int i;
	struct kvm_vcpu *vcpu;

	kvm_for_each_vcpu(i, vcpu, kvm) {
		if (!kvm_arm_pmu_irq_initialized(vcpu))
			continue;

		if (irq_is_ppi(irq)) {
			if (vcpu->arch.pmu.irq_num != irq)
				return false;
		} else {
			if (vcpu->arch.pmu.irq_num == irq)
				return false;
		}
	}

	return true;
}

int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
	if (!kvm_arm_support_pmu_v3() ||
	    !test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
		return -ENODEV;

	if (vcpu->arch.pmu.created)
		return -EBUSY;

	if (!vcpu->kvm->arch.pmuver)
		vcpu->kvm->arch.pmuver = kvm_pmu_probe_pmuver();

	if (vcpu->kvm->arch.pmuver == 0xf)
		return -ENODEV;

	switch (attr->attr) {
	case KVM_ARM_VCPU_PMU_V3_IRQ: {
		int __user *uaddr = (int __user *)(long)attr->addr;
		int irq;

		if (!irqchip_in_kernel(vcpu->kvm))
			return -EINVAL;

		if (get_user(irq, uaddr))
			return -EFAULT;

		/* The PMU overflow interrupt can be a PPI or a valid SPI. */
		if (!(irq_is_ppi(irq) || irq_is_spi(irq)))
			return -EINVAL;

		if (!pmu_irq_is_valid(vcpu->kvm, irq))
			return -EINVAL;

		if (kvm_arm_pmu_irq_initialized(vcpu))
			return -EBUSY;

		kvm_debug("Set kvm ARM PMU irq: %d\n", irq);
		vcpu->arch.pmu.irq_num = irq;
		return 0;
	}
	case KVM_ARM_VCPU_PMU_V3_FILTER: {
		struct kvm_pmu_event_filter __user *uaddr;
		struct kvm_pmu_event_filter filter;
		int nr_events;

		nr_events = kvm_pmu_event_mask(vcpu->kvm) + 1;

		uaddr = (struct kvm_pmu_event_filter __user *)(long)attr->addr;

		if (copy_from_user(&filter, uaddr, sizeof(filter)))
			return -EFAULT;

		if (((u32)filter.base_event + filter.nevents) > nr_events ||
		    (filter.action != KVM_PMU_EVENT_ALLOW &&
		     filter.action != KVM_PMU_EVENT_DENY))
			return -EINVAL;

		mutex_lock(&vcpu->kvm->lock);

		if (!vcpu->kvm->arch.pmu_filter) {
			vcpu->kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL);
			if (!vcpu->kvm->arch.pmu_filter) {
				mutex_unlock(&vcpu->kvm->lock);
				return -ENOMEM;
			}

			/*
			 * The default depends on the first applied filter.
			 * If it allows events, the default is to deny.
			 * Conversely, if the first filter denies a set of
			 * events, the default is to allow.
			 */
			if (filter.action == KVM_PMU_EVENT_ALLOW)
				bitmap_zero(vcpu->kvm->arch.pmu_filter, nr_events);
			else
				bitmap_fill(vcpu->kvm->arch.pmu_filter, nr_events);
		}

		if (filter.action == KVM_PMU_EVENT_ALLOW)
			bitmap_set(vcpu->kvm->arch.pmu_filter, filter.base_event, filter.nevents);
		else
			bitmap_clear(vcpu->kvm->arch.pmu_filter, filter.base_event, filter.nevents);

		mutex_unlock(&vcpu->kvm->lock);

		return 0;
	}
	case KVM_ARM_VCPU_PMU_V3_INIT:
		return kvm_arm_pmu_v3_init(vcpu);
	}

	return -ENXIO;
}

int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
	switch (attr->attr) {
	case KVM_ARM_VCPU_PMU_V3_IRQ: {
		int __user *uaddr = (int __user *)(long)attr->addr;
		int irq;

		if (!irqchip_in_kernel(vcpu->kvm))
			return -EINVAL;

		if (!test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
			return -ENODEV;

		if (!kvm_arm_pmu_irq_initialized(vcpu))
			return -ENXIO;

		irq = vcpu->arch.pmu.irq_num;
		return put_user(irq, uaddr);
	}
	}

	return -ENXIO;
}

int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
	switch (attr->attr) {
	case KVM_ARM_VCPU_PMU_V3_IRQ:
	case KVM_ARM_VCPU_PMU_V3_INIT:
	case KVM_ARM_VCPU_PMU_V3_FILTER:
		if (kvm_arm_support_pmu_v3() &&
		    test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
			return 0;
	}

	return -ENXIO;
}