/*
 * Copyright (C) 2015 Linaro Ltd.
 * Author: Shannon Zhao <shannon.zhao@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

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

/**
 * 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, reg, enabled, running;
	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;
	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 & pmc->bitmask;
}

/**
 * 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);
}

/**
 * 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;

	if (pmc->perf_event) {
		counter = kvm_pmu_get_counter_value(vcpu, pmc->idx);
		reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
		       ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
		vcpu_sys_reg(vcpu, reg) = counter;
		perf_event_disable(pmc->perf_event);
		perf_event_release_kernel(pmc->perf_event);
		pmc->perf_event = NULL;
	}
}

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 - enable selected PMU counter
 * @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(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];
		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 - disable selected PMU counter
 * @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(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];
		if (pmc->perf_event)
			perf_event_disable(pmc->perf_event);
	}
}

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_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)
{
	struct kvm_pmu *pmu = &vcpu->arch.pmu;
	struct kvm_pmc *pmc = &pmu->pmc[select_idx];
	struct perf_event *event;
	struct perf_event_attr attr;
	u64 eventsel, counter;

	kvm_pmu_stop_counter(vcpu, pmc);
	eventsel = data & ARMV8_PMU_EVTYPE_EVENT;

	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, select_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_counter_value(vcpu, select_idx);
	/* The initial sample period (overflow count) of an event. */
	attr.sample_period = (-counter) & pmc->bitmask;

	event = perf_event_create_kernel_counter(&attr, -1, current, NULL, pmc);
	if (IS_ERR(event)) {
		pr_err_once("kvm: pmu event creation failed %ld\n",
			    PTR_ERR(event));
		return;
	}

	pmc->perf_event = event;
}