// SPDX-License-Identifier: GPL-2.0+
// Copyright 2017 IBM Corp.
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <uapi/misc/ocxl.h>
#include <asm/reg.h>
#include <asm/switch_to.h>
#include "ocxl_internal.h"


#define OCXL_NUM_MINORS 256 /* Total to reserve */

static dev_t ocxl_dev;
static struct class *ocxl_class;
static struct mutex minors_idr_lock;
static struct idr minors_idr;

static struct ocxl_afu *find_and_get_afu(dev_t devno)
{
        struct ocxl_afu *afu;
        int afu_minor;

        afu_minor = MINOR(devno);
        /*
         * We don't declare an RCU critical section here, as our AFU
         * is protected by a reference counter on the device. By the time the
         * minor number of a device is removed from the idr, the ref count of
         * the device is already at 0, so no user API will access that AFU and
         * this function can't return it.
         */
        afu = idr_find(&minors_idr, afu_minor);
        if (afu)
                ocxl_afu_get(afu);
        return afu;
}

static int allocate_afu_minor(struct ocxl_afu *afu)
{
        int minor;

        mutex_lock(&minors_idr_lock);
        minor = idr_alloc(&minors_idr, afu, 0, OCXL_NUM_MINORS, GFP_KERNEL);
        mutex_unlock(&minors_idr_lock);
        return minor;
}

static void free_afu_minor(struct ocxl_afu *afu)
{
        mutex_lock(&minors_idr_lock);
        idr_remove(&minors_idr, MINOR(afu->dev.devt));
        mutex_unlock(&minors_idr_lock);
}

static int afu_open(struct inode *inode, struct file *file)
{
        struct ocxl_afu *afu;
        struct ocxl_context *ctx;
        int rc;

        pr_debug("%s for device %x\n", __func__, inode->i_rdev);

        afu = find_and_get_afu(inode->i_rdev);
        if (!afu)
                return -ENODEV;

        ctx = ocxl_context_alloc();
        if (!ctx) {
                rc = -ENOMEM;
                goto put_afu;
        }

        rc = ocxl_context_init(ctx, afu, inode->i_mapping);
        if (rc)
                goto put_afu;
        file->private_data = ctx;
        ocxl_afu_put(afu);
        return 0;

put_afu:
        ocxl_afu_put(afu);
        return rc;
}

static long afu_ioctl_attach(struct ocxl_context *ctx,
                        struct ocxl_ioctl_attach __user *uarg)
{
        struct ocxl_ioctl_attach arg;
        u64 amr = 0;
        int rc;

        pr_debug("%s for context %d\n", __func__, ctx->pasid);

        if (copy_from_user(&arg, uarg, sizeof(arg)))
                return -EFAULT;

        /* Make sure reserved fields are not set for forward compatibility */
        if (arg.reserved1 || arg.reserved2 || arg.reserved3)
                return -EINVAL;

        amr = arg.amr & mfspr(SPRN_UAMOR);
        rc = ocxl_context_attach(ctx, amr);
        return rc;
}

static long afu_ioctl_get_metadata(struct ocxl_context *ctx,
                struct ocxl_ioctl_metadata __user *uarg)
{
        struct ocxl_ioctl_metadata arg;

        memset(&arg, 0, sizeof(arg));

        arg.version = 0;

        arg.afu_version_major = ctx->afu->config.version_major;
        arg.afu_version_minor = ctx->afu->config.version_minor;
        arg.pasid = ctx->pasid;
        arg.pp_mmio_size = ctx->afu->config.pp_mmio_stride;
        arg.global_mmio_size = ctx->afu->config.global_mmio_size;

        if (copy_to_user(uarg, &arg, sizeof(arg)))
                return -EFAULT;

        return 0;
}

#ifdef CONFIG_PPC64
static long afu_ioctl_enable_p9_wait(struct ocxl_context *ctx,
                struct ocxl_ioctl_p9_wait __user *uarg)
{
        struct ocxl_ioctl_p9_wait arg;

        memset(&arg, 0, sizeof(arg));

        if (cpu_has_feature(CPU_FTR_P9_TIDR)) {
                enum ocxl_context_status status;

                // Locks both status & tidr
                mutex_lock(&ctx->status_mutex);
                if (!ctx->tidr) {
                        if (set_thread_tidr(current)) {
                                mutex_unlock(&ctx->status_mutex);
                                return -ENOENT;
                        }

                        ctx->tidr = current->thread.tidr;
                }

                status = ctx->status;
                mutex_unlock(&ctx->status_mutex);

                if (status == ATTACHED) {
                        int rc;
                        struct link *link = ctx->afu->fn->link;

                        rc = ocxl_link_update_pe(link, ctx->pasid, ctx->tidr);
                        if (rc)
                                return rc;
                }

                arg.thread_id = ctx->tidr;
        } else
                return -ENOENT;

        if (copy_to_user(uarg, &arg, sizeof(arg)))
                return -EFAULT;

        return 0;
}
#endif


static long afu_ioctl_get_features(struct ocxl_context *ctx,
                struct ocxl_ioctl_features __user *uarg)
{
        struct ocxl_ioctl_features arg;

        memset(&arg, 0, sizeof(arg));

#ifdef CONFIG_PPC64
        if (cpu_has_feature(CPU_FTR_P9_TIDR))
                arg.flags[0] |= OCXL_IOCTL_FEATURES_FLAGS0_P9_WAIT;
#endif

        if (copy_to_user(uarg, &arg, sizeof(arg)))
                return -EFAULT;

        return 0;
}

#define CMD_STR(x) (x == OCXL_IOCTL_ATTACH ? "ATTACH" :                 \
                        x == OCXL_IOCTL_IRQ_ALLOC ? "IRQ_ALLOC" :       \
                        x == OCXL_IOCTL_IRQ_FREE ? "IRQ_FREE" :         \
                        x == OCXL_IOCTL_IRQ_SET_FD ? "IRQ_SET_FD" :     \
                        x == OCXL_IOCTL_GET_METADATA ? "GET_METADATA" : \
                        x == OCXL_IOCTL_ENABLE_P9_WAIT ? "ENABLE_P9_WAIT" :     \
                        x == OCXL_IOCTL_GET_FEATURES ? "GET_FEATURES" : \
                        "UNKNOWN")

static long afu_ioctl(struct file *file, unsigned int cmd,
                unsigned long args)
{
        struct ocxl_context *ctx = file->private_data;
        struct ocxl_ioctl_irq_fd irq_fd;
        u64 irq_offset;
        long rc;

        pr_debug("%s for context %d, command %s\n", __func__, ctx->pasid,
                CMD_STR(cmd));

        if (ctx->status == CLOSED)
                return -EIO;

        switch (cmd) {
        case OCXL_IOCTL_ATTACH:
                rc = afu_ioctl_attach(ctx,
                                (struct ocxl_ioctl_attach __user *) args);
                break;

        case OCXL_IOCTL_IRQ_ALLOC:
                rc = ocxl_afu_irq_alloc(ctx, &irq_offset);
                if (!rc) {
                        rc = copy_to_user((u64 __user *) args, &irq_offset,
                                        sizeof(irq_offset));
                        if (rc) {
                                ocxl_afu_irq_free(ctx, irq_offset);
                                return -EFAULT;
                        }
                }
                break;

        case OCXL_IOCTL_IRQ_FREE:
                rc = copy_from_user(&irq_offset, (u64 __user *) args,
                                sizeof(irq_offset));
                if (rc)
                        return -EFAULT;
                rc = ocxl_afu_irq_free(ctx, irq_offset);
                break;

        case OCXL_IOCTL_IRQ_SET_FD:
                rc = copy_from_user(&irq_fd, (u64 __user *) args,
                                sizeof(irq_fd));
                if (rc)
                        return -EFAULT;
                if (irq_fd.reserved)
                        return -EINVAL;
                rc = ocxl_afu_irq_set_fd(ctx, irq_fd.irq_offset,
                                        irq_fd.eventfd);
                break;

        case OCXL_IOCTL_GET_METADATA:
                rc = afu_ioctl_get_metadata(ctx,
                                (struct ocxl_ioctl_metadata __user *) args);
                break;

#ifdef CONFIG_PPC64
        case OCXL_IOCTL_ENABLE_P9_WAIT:
                rc = afu_ioctl_enable_p9_wait(ctx,
                                (struct ocxl_ioctl_p9_wait __user *) args);
                break;
#endif

        case OCXL_IOCTL_GET_FEATURES:
                rc = afu_ioctl_get_features(ctx,
                                (struct ocxl_ioctl_features __user *) args);
                break;

        default:
                rc = -EINVAL;
        }
        return rc;
}

static long afu_compat_ioctl(struct file *file, unsigned int cmd,
                        unsigned long args)
{
        return afu_ioctl(file, cmd, args);
}

static int afu_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct ocxl_context *ctx = file->private_data;

        pr_debug("%s for context %d\n", __func__, ctx->pasid);
        return ocxl_context_mmap(ctx, vma);
}

static bool has_xsl_error(struct ocxl_context *ctx)
{
        bool ret;

        mutex_lock(&ctx->xsl_error_lock);
        ret = !!ctx->xsl_error.addr;
        mutex_unlock(&ctx->xsl_error_lock);

        return ret;
}

/*
 * Are there any events pending on the AFU
 * ctx: The AFU context
 * Returns: true if there are events pending
 */
static bool afu_events_pending(struct ocxl_context *ctx)
{
        if (has_xsl_error(ctx))
                return true;
        return false;
}

static unsigned int afu_poll(struct file *file, struct poll_table_struct *wait)
{
        struct ocxl_context *ctx = file->private_data;
        unsigned int mask = 0;
        bool closed;

        pr_debug("%s for context %d\n", __func__, ctx->pasid);

        poll_wait(file, &ctx->events_wq, wait);

        mutex_lock(&ctx->status_mutex);
        closed = (ctx->status == CLOSED);
        mutex_unlock(&ctx->status_mutex);

        if (afu_events_pending(ctx))
                mask = EPOLLIN | EPOLLRDNORM;
        else if (closed)
                mask = EPOLLERR;

        return mask;
}

/*
 * Populate the supplied buffer with a single XSL error
 * ctx: The AFU context to report the error from
 * header: the event header to populate
 * buf: The buffer to write the body into (should be at least
 *      AFU_EVENT_BODY_XSL_ERROR_SIZE)
 * Return: the amount of buffer that was populated
 */
static ssize_t append_xsl_error(struct ocxl_context *ctx,
                                struct ocxl_kernel_event_header *header,
                                char __user *buf)
{
        struct ocxl_kernel_event_xsl_fault_error body;

        memset(&body, 0, sizeof(body));

        mutex_lock(&ctx->xsl_error_lock);
        if (!ctx->xsl_error.addr) {
                mutex_unlock(&ctx->xsl_error_lock);
                return 0;
        }

        body.addr = ctx->xsl_error.addr;
        body.dsisr = ctx->xsl_error.dsisr;
        body.count = ctx->xsl_error.count;

        ctx->xsl_error.addr = 0;
        ctx->xsl_error.dsisr = 0;
        ctx->xsl_error.count = 0;

        mutex_unlock(&ctx->xsl_error_lock);

        header->type = OCXL_AFU_EVENT_XSL_FAULT_ERROR;

        if (copy_to_user(buf, &body, sizeof(body)))
                return -EFAULT;

        return sizeof(body);
}

#define AFU_EVENT_BODY_MAX_SIZE sizeof(struct ocxl_kernel_event_xsl_fault_error)

/*
 * Reports events on the AFU
 * Format:
 *      Header (struct ocxl_kernel_event_header)
 *      Body (struct ocxl_kernel_event_*)
 *      Header...
 */
static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
                        loff_t *off)
{
        struct ocxl_context *ctx = file->private_data;
        struct ocxl_kernel_event_header header;
        ssize_t rc;
        ssize_t used = 0;
        DEFINE_WAIT(event_wait);

        memset(&header, 0, sizeof(header));

        /* Require offset to be 0 */
        if (*off != 0)
                return -EINVAL;

        if (count < (sizeof(struct ocxl_kernel_event_header) +
                        AFU_EVENT_BODY_MAX_SIZE))
                return -EINVAL;

        for (;;) {
                prepare_to_wait(&ctx->events_wq, &event_wait,
                                TASK_INTERRUPTIBLE);

                if (afu_events_pending(ctx))
                        break;

                if (ctx->status == CLOSED)
                        break;

                if (file->f_flags & O_NONBLOCK) {
                        finish_wait(&ctx->events_wq, &event_wait);
                        return -EAGAIN;
                }

                if (signal_pending(current)) {
                        finish_wait(&ctx->events_wq, &event_wait);
                        return -ERESTARTSYS;
                }

                schedule();
        }

        finish_wait(&ctx->events_wq, &event_wait);

        if (has_xsl_error(ctx)) {
                used = append_xsl_error(ctx, &header, buf + sizeof(header));
                if (used < 0)
                        return used;
        }

        if (!afu_events_pending(ctx))
                header.flags |= OCXL_KERNEL_EVENT_FLAG_LAST;

        if (copy_to_user(buf, &header, sizeof(header)))
                return -EFAULT;

        used += sizeof(header);

        rc = used;
        return rc;
}

static int afu_release(struct inode *inode, struct file *file)
{
        struct ocxl_context *ctx = file->private_data;
        int rc;

        pr_debug("%s for device %x\n", __func__, inode->i_rdev);
        rc = ocxl_context_detach(ctx);
        mutex_lock(&ctx->mapping_lock);
        ctx->mapping = NULL;
        mutex_unlock(&ctx->mapping_lock);
        wake_up_all(&ctx->events_wq);
        if (rc != -EBUSY)
                ocxl_context_free(ctx);
        return 0;
}

static const struct file_operations ocxl_afu_fops = {
        .owner          = THIS_MODULE,
        .open           = afu_open,
        .unlocked_ioctl = afu_ioctl,
        .compat_ioctl   = afu_compat_ioctl,
        .mmap           = afu_mmap,
        .poll           = afu_poll,
        .read           = afu_read,
        .release        = afu_release,
};

int ocxl_create_cdev(struct ocxl_afu *afu)
{
        int rc;

        cdev_init(&afu->cdev, &ocxl_afu_fops);
        rc = cdev_add(&afu->cdev, afu->dev.devt, 1);
        if (rc) {
                dev_err(&afu->dev, "Unable to add afu char device: %d\n", rc);
                return rc;
        }
        return 0;
}

void ocxl_destroy_cdev(struct ocxl_afu *afu)
{
        cdev_del(&afu->cdev);
}

int ocxl_register_afu(struct ocxl_afu *afu)
{
        int minor;

        minor = allocate_afu_minor(afu);
        if (minor < 0)
                return minor;
        afu->dev.devt = MKDEV(MAJOR(ocxl_dev), minor);
        afu->dev.class = ocxl_class;
        return device_register(&afu->dev);
}

void ocxl_unregister_afu(struct ocxl_afu *afu)
{
        free_afu_minor(afu);
}

static char *ocxl_devnode(struct device *dev, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "ocxl/%s", dev_name(dev));
}

int ocxl_file_init(void)
{
        int rc;

        mutex_init(&minors_idr_lock);
        idr_init(&minors_idr);

        rc = alloc_chrdev_region(&ocxl_dev, 0, OCXL_NUM_MINORS, "ocxl");
        if (rc) {
                pr_err("Unable to allocate ocxl major number: %d\n", rc);
                return rc;
        }

        ocxl_class = class_create(THIS_MODULE, "ocxl");
        if (IS_ERR(ocxl_class)) {
                pr_err("Unable to create ocxl class\n");
                unregister_chrdev_region(ocxl_dev, OCXL_NUM_MINORS);
                return PTR_ERR(ocxl_class);
        }

        ocxl_class->devnode = ocxl_devnode;
        return 0;
}

void ocxl_file_exit(void)
{
        class_destroy(ocxl_class);
        unregister_chrdev_region(ocxl_dev, OCXL_NUM_MINORS);
        idr_destroy(&minors_idr);
}