/*
 * Copyright (C) 2015, 2016 ARM Ltd.
 *
 * 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/uaccess.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/kvm_host.h>
#include <kvm/arm_vgic.h>
#include <asm/kvm_mmu.h>
#include "vgic.h"

/*
 * Initialization rules: there are multiple stages to the vgic
 * initialization, both for the distributor and the CPU interfaces.  The basic
 * idea is that even though the VGIC is not functional or not requested from
 * user space, the critical path of the run loop can still call VGIC functions
 * that just won't do anything, without them having to check additional
 * initialization flags to ensure they don't look at uninitialized data
 * structures.
 *
 * Distributor:
 *
 * - kvm_vgic_early_init(): initialization of static data that doesn't
 *   depend on any sizing information or emulation type. No allocation
 *   is allowed there.
 *
 * - vgic_init(): allocation and initialization of the generic data
 *   structures that depend on sizing information (number of CPUs,
 *   number of interrupts). Also initializes the vcpu specific data
 *   structures. Can be executed lazily for GICv2.
 *
 * CPU Interface:
 *
 * - kvm_vgic_vcpu_early_init(): initialization of static data that
 *   doesn't depend on any sizing information or emulation type. No
 *   allocation is allowed there.
 */

/* EARLY INIT */

/**
 * kvm_vgic_early_init() - Initialize static VGIC VCPU data structures
 * @kvm: The VM whose VGIC districutor should be initialized
 *
 * Only do initialization of static structures that don't require any
 * allocation or sizing information from userspace.  vgic_init() called
 * kvm_vgic_dist_init() which takes care of the rest.
 */
void kvm_vgic_early_init(struct kvm *kvm)
{
        struct vgic_dist *dist = &kvm->arch.vgic;

        INIT_LIST_HEAD(&dist->lpi_list_head);
        spin_lock_init(&dist->lpi_list_lock);
}

/**
 * kvm_vgic_vcpu_early_init() - Initialize static VGIC VCPU data structures
 * @vcpu: The VCPU whose VGIC data structures whould be initialized
 *
 * Only do initialization, but do not actually enable the VGIC CPU interface
 * yet.
 */
void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
        int i;

        INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
        spin_lock_init(&vgic_cpu->ap_list_lock);

        /*
         * Enable and configure all SGIs to be edge-triggered and
         * configure all PPIs as level-triggered.
         */
        for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
                struct vgic_irq *irq = &vgic_cpu->private_irqs[i];

                INIT_LIST_HEAD(&irq->ap_list);
                spin_lock_init(&irq->irq_lock);
                irq->intid = i;
                irq->vcpu = NULL;
                irq->target_vcpu = vcpu;
                irq->targets = 1U << vcpu->vcpu_id;
                kref_init(&irq->refcount);
                if (vgic_irq_is_sgi(i)) {
                        /* SGIs */
                        irq->enabled = 1;
                        irq->config = VGIC_CONFIG_EDGE;
                } else {
                        /* PPIs */
                        irq->config = VGIC_CONFIG_LEVEL;
                }
        }
}

/* CREATION */

/**
 * kvm_vgic_create: triggered by the instantiation of the VGIC device by
 * user space, either through the legacy KVM_CREATE_IRQCHIP ioctl (v2 only)
 * or through the generic KVM_CREATE_DEVICE API ioctl.
 * irqchip_in_kernel() tells you if this function succeeded or not.
 * @kvm: kvm struct pointer
 * @type: KVM_DEV_TYPE_ARM_VGIC_V[23]
 */
int kvm_vgic_create(struct kvm *kvm, u32 type)
{
        int i, vcpu_lock_idx = -1, ret;
        struct kvm_vcpu *vcpu;

        if (irqchip_in_kernel(kvm))
                return -EEXIST;

        /*
         * This function is also called by the KVM_CREATE_IRQCHIP handler,
         * which had no chance yet to check the availability of the GICv2
         * emulation. So check this here again. KVM_CREATE_DEVICE does
         * the proper checks already.
         */
        if (type == KVM_DEV_TYPE_ARM_VGIC_V2 &&
                !kvm_vgic_global_state.can_emulate_gicv2)
                return -ENODEV;

        /*
         * Any time a vcpu is run, vcpu_load is called which tries to grab the
         * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
         * that no other VCPUs are run while we create the vgic.
         */
        ret = -EBUSY;
        kvm_for_each_vcpu(i, vcpu, kvm) {
                if (!mutex_trylock(&vcpu->mutex))
                        goto out_unlock;
                vcpu_lock_idx = i;
        }

        kvm_for_each_vcpu(i, vcpu, kvm) {
                if (vcpu->arch.has_run_once)
                        goto out_unlock;
        }
        ret = 0;

        if (type == KVM_DEV_TYPE_ARM_VGIC_V2)
                kvm->arch.max_vcpus = VGIC_V2_MAX_CPUS;
        else
                kvm->arch.max_vcpus = VGIC_V3_MAX_CPUS;

        if (atomic_read(&kvm->online_vcpus) > kvm->arch.max_vcpus) {
                ret = -E2BIG;
                goto out_unlock;
        }

        kvm->arch.vgic.in_kernel = true;
        kvm->arch.vgic.vgic_model = type;

        /*
         * kvm_vgic_global_state.vctrl_base is set on vgic probe (kvm_arch_init)
         * it is stored in distributor struct for asm save/restore purpose
         */
        kvm->arch.vgic.vctrl_base = kvm_vgic_global_state.vctrl_base;

        kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF;
        kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF;
        kvm->arch.vgic.vgic_redist_base = VGIC_ADDR_UNDEF;

out_unlock:
        for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
                vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
                mutex_unlock(&vcpu->mutex);
        }
        return ret;
}

/* INIT/DESTROY */

/**
 * kvm_vgic_dist_init: initialize the dist data structures
 * @kvm: kvm struct pointer
 * @nr_spis: number of spis, frozen by caller
 */
static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
{
        struct vgic_dist *dist = &kvm->arch.vgic;
        struct kvm_vcpu *vcpu0 = kvm_get_vcpu(kvm, 0);
        int i;

        dist->spis = kcalloc(nr_spis, sizeof(struct vgic_irq), GFP_KERNEL);
        if (!dist->spis)
                return  -ENOMEM;

        /*
         * In the following code we do not take the irq struct lock since
         * no other action on irq structs can happen while the VGIC is
         * not initialized yet:
         * If someone wants to inject an interrupt or does a MMIO access, we
         * require prior initialization in case of a virtual GICv3 or trigger
         * initialization when using a virtual GICv2.
         */
        for (i = 0; i < nr_spis; i++) {
                struct vgic_irq *irq = &dist->spis[i];

                irq->intid = i + VGIC_NR_PRIVATE_IRQS;
                INIT_LIST_HEAD(&irq->ap_list);
                spin_lock_init(&irq->irq_lock);
                irq->vcpu = NULL;
                irq->target_vcpu = vcpu0;
                kref_init(&irq->refcount);
                if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2)
                        irq->targets = 0;
                else
                        irq->mpidr = 0;
        }
        return 0;
}

/**
 * kvm_vgic_vcpu_init() - Register VCPU-specific KVM iodevs
 * @vcpu: pointer to the VCPU being created and initialized
 */
int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
{
        int ret = 0;
        struct vgic_dist *dist = &vcpu->kvm->arch.vgic;

        if (!irqchip_in_kernel(vcpu->kvm))
                return 0;

        /*
         * If we are creating a VCPU with a GICv3 we must also register the
         * KVM io device for the redistributor that belongs to this VCPU.
         */
        if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) {
                mutex_lock(&vcpu->kvm->lock);
                ret = vgic_register_redist_iodev(vcpu);
                mutex_unlock(&vcpu->kvm->lock);
        }
        return ret;
}

static void kvm_vgic_vcpu_enable(struct kvm_vcpu *vcpu)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_enable(vcpu);
        else
                vgic_v3_enable(vcpu);
}

/*
 * vgic_init: allocates and initializes dist and vcpu data structures
 * depending on two dimensioning parameters:
 * - the number of spis
 * - the number of vcpus
 * The function is generally called when nr_spis has been explicitly set
 * by the guest through the KVM DEVICE API. If not nr_spis is set to 256.
 * vgic_initialized() returns true when this function has succeeded.
 * Must be called with kvm->lock held!
 */
int vgic_init(struct kvm *kvm)
{
        struct vgic_dist *dist = &kvm->arch.vgic;
        struct kvm_vcpu *vcpu;
        int ret = 0, i;

        if (vgic_initialized(kvm))
                return 0;

        /* freeze the number of spis */
        if (!dist->nr_spis)
                dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;

        ret = kvm_vgic_dist_init(kvm, dist->nr_spis);
        if (ret)
                goto out;

        if (vgic_has_its(kvm)) {
                ret = vgic_v4_init(kvm);
                if (ret)
                        goto out;
        }

        kvm_for_each_vcpu(i, vcpu, kvm)
                kvm_vgic_vcpu_enable(vcpu);

        ret = kvm_vgic_setup_default_irq_routing(kvm);
        if (ret)
                goto out;

        vgic_debug_init(kvm);

        dist->initialized = true;

        /*
         * If we're initializing GICv2 on-demand when first running the VCPU
         * then we need to load the VGIC state onto the CPU.  We can detect
         * this easily by checking if we are in between vcpu_load and vcpu_put
         * when we just initialized the VGIC.
         */
        preempt_disable();
        vcpu = kvm_arm_get_running_vcpu();
        if (vcpu)
                kvm_vgic_load(vcpu);
        preempt_enable();
out:
        return ret;
}

static void kvm_vgic_dist_destroy(struct kvm *kvm)
{
        struct vgic_dist *dist = &kvm->arch.vgic;

        dist->ready = false;
        dist->initialized = false;

        kfree(dist->spis);
        dist->nr_spis = 0;

        if (vgic_supports_direct_msis(kvm))
                vgic_v4_teardown(kvm);
}

void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;

        INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
}

/* To be called with kvm->lock held */
static void __kvm_vgic_destroy(struct kvm *kvm)
{
        struct kvm_vcpu *vcpu;
        int i;

        vgic_debug_destroy(kvm);

        kvm_vgic_dist_destroy(kvm);

        kvm_for_each_vcpu(i, vcpu, kvm)
                kvm_vgic_vcpu_destroy(vcpu);
}

void kvm_vgic_destroy(struct kvm *kvm)
{
        mutex_lock(&kvm->lock);
        __kvm_vgic_destroy(kvm);
        mutex_unlock(&kvm->lock);
}

/**
 * vgic_lazy_init: Lazy init is only allowed if the GIC exposed to the guest
 * is a GICv2. A GICv3 must be explicitly initialized by the guest using the
 * KVM_DEV_ARM_VGIC_GRP_CTRL KVM_DEVICE group.
 * @kvm: kvm struct pointer
 */
int vgic_lazy_init(struct kvm *kvm)
{
        int ret = 0;

        if (unlikely(!vgic_initialized(kvm))) {
                /*
                 * We only provide the automatic initialization of the VGIC
                 * for the legacy case of a GICv2. Any other type must
                 * be explicitly initialized once setup with the respective
                 * KVM device call.
                 */
                if (kvm->arch.vgic.vgic_model != KVM_DEV_TYPE_ARM_VGIC_V2)
                        return -EBUSY;

                mutex_lock(&kvm->lock);
                ret = vgic_init(kvm);
                mutex_unlock(&kvm->lock);
        }

        return ret;
}

/* RESOURCE MAPPING */

/**
 * Map the MMIO regions depending on the VGIC model exposed to the guest
 * called on the first VCPU run.
 * Also map the virtual CPU interface into the VM.
 * v2/v3 derivatives call vgic_init if not already done.
 * vgic_ready() returns true if this function has succeeded.
 * @kvm: kvm struct pointer
 */
int kvm_vgic_map_resources(struct kvm *kvm)
{
        struct vgic_dist *dist = &kvm->arch.vgic;
        int ret = 0;

        mutex_lock(&kvm->lock);
        if (!irqchip_in_kernel(kvm))
                goto out;

        if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2)
                ret = vgic_v2_map_resources(kvm);
        else
                ret = vgic_v3_map_resources(kvm);

        if (ret)
                __kvm_vgic_destroy(kvm);

out:
        mutex_unlock(&kvm->lock);
        return ret;
}

/* GENERIC PROBE */

static int vgic_init_cpu_starting(unsigned int cpu)
{
        enable_percpu_irq(kvm_vgic_global_state.maint_irq, 0);
        return 0;
}


static int vgic_init_cpu_dying(unsigned int cpu)
{
        disable_percpu_irq(kvm_vgic_global_state.maint_irq);
        return 0;
}

static irqreturn_t vgic_maintenance_handler(int irq, void *data)
{
        /*
         * We cannot rely on the vgic maintenance interrupt to be
         * delivered synchronously. This means we can only use it to
         * exit the VM, and we perform the handling of EOIed
         * interrupts on the exit path (see vgic_process_maintenance).
         */
        return IRQ_HANDLED;
}

/**
 * kvm_vgic_init_cpu_hardware - initialize the GIC VE hardware
 *
 * For a specific CPU, initialize the GIC VE hardware.
 */
void kvm_vgic_init_cpu_hardware(void)
{
        BUG_ON(preemptible());

        /*
         * We want to make sure the list registers start out clear so that we
         * only have the program the used registers.
         */
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_init_lrs();
        else
                kvm_call_hyp(__vgic_v3_init_lrs);
}

/**
 * kvm_vgic_hyp_init: populates the kvm_vgic_global_state variable
 * according to the host GIC model. Accordingly calls either
 * vgic_v2/v3_probe which registers the KVM_DEVICE that can be
 * instantiated by a guest later on .
 */
int kvm_vgic_hyp_init(void)
{
        const struct gic_kvm_info *gic_kvm_info;
        int ret;

        gic_kvm_info = gic_get_kvm_info();
        if (!gic_kvm_info)
                return -ENODEV;

        if (!gic_kvm_info->maint_irq) {
                kvm_err("No vgic maintenance irq\n");
                return -ENXIO;
        }

        switch (gic_kvm_info->type) {
        case GIC_V2:
                ret = vgic_v2_probe(gic_kvm_info);
                break;
        case GIC_V3:
                ret = vgic_v3_probe(gic_kvm_info);
                if (!ret) {
                        static_branch_enable(&kvm_vgic_global_state.gicv3_cpuif);
                        kvm_info("GIC system register CPU interface enabled\n");
                }
                break;
        default:
                ret = -ENODEV;
        };

        if (ret)
                return ret;

        kvm_vgic_global_state.maint_irq = gic_kvm_info->maint_irq;
        ret = request_percpu_irq(kvm_vgic_global_state.maint_irq,
                                 vgic_maintenance_handler,
                                 "vgic", kvm_get_running_vcpus());
        if (ret) {
                kvm_err("Cannot register interrupt %d\n",
                        kvm_vgic_global_state.maint_irq);
                return ret;
        }

        ret = cpuhp_setup_state(CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING,
                                "kvm/arm/vgic:starting",
                                vgic_init_cpu_starting, vgic_init_cpu_dying);
        if (ret) {
                kvm_err("Cannot register vgic CPU notifier\n");
                goto out_free_irq;
        }

        kvm_info("vgic interrupt IRQ%d\n", kvm_vgic_global_state.maint_irq);
        return 0;

out_free_irq:
        free_percpu_irq(kvm_vgic_global_state.maint_irq,
                        kvm_get_running_vcpus());
        return ret;
}