// SPDX-License-Identifier: GPL-2.0
/*
 * VFIO based Physical Subchannel device driver
 *
 * Copyright IBM Corp. 2017
 * Copyright Red Hat, Inc. 2019
 *
 * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
 *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
 *            Cornelia Huck <cohuck@redhat.com>
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/mdev.h>

#include <asm/isc.h>

#include "chp.h"
#include "ioasm.h"
#include "css.h"
#include "vfio_ccw_private.h"

struct workqueue_struct *vfio_ccw_work_q;
struct kmem_cache *vfio_ccw_io_region;
struct kmem_cache *vfio_ccw_cmd_region;
struct kmem_cache *vfio_ccw_schib_region;
struct kmem_cache *vfio_ccw_crw_region;

debug_info_t *vfio_ccw_debug_msg_id;
debug_info_t *vfio_ccw_debug_trace_id;

/*
 * Helpers
 */
int vfio_ccw_sch_quiesce(struct subchannel *sch)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
        struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);
        DECLARE_COMPLETION_ONSTACK(completion);
        int iretry, ret = 0;

        /*
         * Probably an impossible situation, after being called through
         * FSM callbacks. But in the event it did, register a warning
         * and return as if things were fine.
         */
        if (WARN_ON(!private))
                return 0;

        iretry = 255;
        do {

                ret = cio_cancel_halt_clear(sch, &iretry);

                if (ret == -EIO) {
                        pr_err("vfio_ccw: could not quiesce subchannel 0.%x.%04x!\n",
                               sch->schid.ssid, sch->schid.sch_no);
                        break;
                }

                /*
                 * Flush all I/O and wait for
                 * cancel/halt/clear completion.
                 */
                private->completion = &completion;
                spin_unlock_irq(&sch->lock);

                if (ret == -EBUSY)
                        wait_for_completion_timeout(&completion, 3*HZ);

                private->completion = NULL;
                flush_workqueue(vfio_ccw_work_q);
                spin_lock_irq(&sch->lock);
                ret = cio_disable_subchannel(sch);
        } while (ret == -EBUSY);

        return ret;
}

void vfio_ccw_sch_io_todo(struct work_struct *work)
{
        struct vfio_ccw_private *private;
        struct irb *irb;
        bool is_final;
        bool cp_is_finished = false;

        private = container_of(work, struct vfio_ccw_private, io_work);
        irb = &private->irb;

        is_final = !(scsw_actl(&irb->scsw) &
                     (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT));
        if (scsw_is_solicited(&irb->scsw)) {
                cp_update_scsw(&private->cp, &irb->scsw);
                if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) {
                        cp_free(&private->cp);
                        cp_is_finished = true;
                }
        }
        mutex_lock(&private->io_mutex);
        memcpy(private->io_region->irb_area, irb, sizeof(*irb));
        mutex_unlock(&private->io_mutex);

        /*
         * Reset to IDLE only if processing of a channel program
         * has finished. Do not overwrite a possible processing
         * state if the interrupt was unsolicited, or if the final
         * interrupt was for HSCH or CSCH.
         */
        if (cp_is_finished)
                private->state = VFIO_CCW_STATE_IDLE;

        if (private->io_trigger)
                eventfd_signal(private->io_trigger);
}

void vfio_ccw_crw_todo(struct work_struct *work)
{
        struct vfio_ccw_private *private;

        private = container_of(work, struct vfio_ccw_private, crw_work);

        if (!list_empty(&private->crw) && private->crw_trigger)
                eventfd_signal(private->crw_trigger);
}

/*
 * Css driver callbacks
 */
static void vfio_ccw_sch_irq(struct subchannel *sch)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
        struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);

        /*
         * The subchannel should still be disabled at this point,
         * so an interrupt would be quite surprising. As with an
         * interrupt while the FSM is closed, let's attempt to
         * disable the subchannel again.
         */
        if (!private) {
                VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: unexpected interrupt\n",
                                   sch->schid.cssid, sch->schid.ssid,
                                   sch->schid.sch_no);

                cio_disable_subchannel(sch);
                return;
        }

        inc_irq_stat(IRQIO_CIO);
        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
}

static void vfio_ccw_free_parent(struct device *dev)
{
        struct vfio_ccw_parent *parent = container_of(dev, struct vfio_ccw_parent, dev);

        kfree(parent);
}

static int vfio_ccw_sch_probe(struct subchannel *sch)
{
        struct pmcw *pmcw = &sch->schib.pmcw;
        struct vfio_ccw_parent *parent;
        int ret = -ENOMEM;

        if (pmcw->qf) {
                dev_warn(&sch->dev, "vfio: ccw: does not support QDIO: %s\n",
                         dev_name(&sch->dev));
                return -ENODEV;
        }

        parent = kzalloc_obj(*parent);
        if (!parent)
                return -ENOMEM;

        dev_set_name(&parent->dev, "parent");
        parent->dev.parent = &sch->dev;
        parent->dev.release = &vfio_ccw_free_parent;
        ret = device_register(&parent->dev);
        if (ret)
                goto out_free;

        dev_set_drvdata(&sch->dev, parent);

        parent->mdev_type.sysfs_name = "io";
        parent->mdev_type.pretty_name = "I/O subchannel (Non-QDIO)";
        parent->mdev_types = &parent->mdev_type;
        ret = mdev_register_parent(&parent->parent, &sch->dev,
                                   &vfio_ccw_mdev_driver,
                                   &parent->mdev_types, 1);
        if (ret)
                goto out_unreg;

        VFIO_CCW_MSG_EVENT(4, "bound to subchannel %x.%x.%04x\n",
                           sch->schid.cssid, sch->schid.ssid,
                           sch->schid.sch_no);
        return 0;

out_unreg:
        device_del(&parent->dev);
out_free:
        put_device(&parent->dev);
        dev_set_drvdata(&sch->dev, NULL);
        return ret;
}

static void vfio_ccw_sch_remove(struct subchannel *sch)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);

        mdev_unregister_parent(&parent->parent);

        device_unregister(&parent->dev);
        dev_set_drvdata(&sch->dev, NULL);

        VFIO_CCW_MSG_EVENT(4, "unbound from subchannel %x.%x.%04x\n",
                           sch->schid.cssid, sch->schid.ssid,
                           sch->schid.sch_no);
}

static void vfio_ccw_sch_shutdown(struct subchannel *sch)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
        struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);

        if (!private)
                return;

        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

/**
 * vfio_ccw_sch_event - process subchannel event
 * @sch: subchannel
 * @process: non-zero if function is called in process context
 *
 * An unspecified event occurred for this subchannel. Adjust data according
 * to the current operational state of the subchannel. Return zero when the
 * event has been handled sufficiently or -EAGAIN when this function should
 * be called again in process context.
 */
static int vfio_ccw_sch_event(struct subchannel *sch, int process)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
        struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);
        unsigned long flags;
        int rc = -EAGAIN;

        spin_lock_irqsave(&sch->lock, flags);
        if (!device_is_registered(&sch->dev))
                goto out_unlock;

        if (work_pending(&sch->todo_work))
                goto out_unlock;

        rc = 0;

        if (cio_update_schib(sch)) {
                if (private)
                        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
        }

out_unlock:
        spin_unlock_irqrestore(&sch->lock, flags);

        return rc;
}

static void vfio_ccw_queue_crw(struct vfio_ccw_private *private,
                               unsigned int rsc,
                               unsigned int erc,
                               unsigned int rsid)
{
        struct vfio_ccw_crw *crw;

        /*
         * If unable to allocate a CRW, just drop the event and
         * carry on.  The guest will either see a later one or
         * learn when it issues its own store subchannel.
         */
        crw = kzalloc_obj(*crw, GFP_ATOMIC);
        if (!crw)
                return;

        /*
         * Build the CRW based on the inputs given to us.
         */
        crw->crw.rsc = rsc;
        crw->crw.erc = erc;
        crw->crw.rsid = rsid;

        list_add_tail(&crw->next, &private->crw);
        queue_work(vfio_ccw_work_q, &private->crw_work);
}

static int vfio_ccw_chp_event(struct subchannel *sch,
                              struct chp_link *link, int event)
{
        struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
        struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);
        int mask = chp_ssd_get_mask(&sch->ssd_info, link);
        int retry = 255;

        if (!private || !mask)
                return 0;

        trace_vfio_ccw_chp_event(sch->schid, mask, event);
        VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: mask=0x%x event=%d\n",
                           sch->schid.cssid,
                           sch->schid.ssid, sch->schid.sch_no,
                           mask, event);

        if (cio_update_schib(sch))
                return -ENODEV;

        switch (event) {
        case CHP_VARY_OFF:
                /* Path logically turned off */
                sch->opm &= ~mask;
                sch->lpm &= ~mask;
                if (sch->schib.pmcw.lpum & mask)
                        cio_cancel_halt_clear(sch, &retry);
                break;
        case CHP_OFFLINE:
                /* Path is gone */
                if (sch->schib.pmcw.lpum & mask)
                        cio_cancel_halt_clear(sch, &retry);
                vfio_ccw_queue_crw(private, CRW_RSC_CPATH, CRW_ERC_PERRN,
                                   link->chpid.id);
                break;
        case CHP_VARY_ON:
                /* Path logically turned on */
                sch->opm |= mask;
                sch->lpm |= mask;
                break;
        case CHP_ONLINE:
                /* Path became available */
                sch->lpm |= mask & sch->opm;
                vfio_ccw_queue_crw(private, CRW_RSC_CPATH, CRW_ERC_INIT,
                                   link->chpid.id);
                break;
        }

        return 0;
}

static struct css_device_id vfio_ccw_sch_ids[] = {
        { .match_flags = 0x1, .type = SUBCHANNEL_TYPE_IO, },
        { /* end of list */ },
};
MODULE_DEVICE_TABLE(css, vfio_ccw_sch_ids);

static struct css_driver vfio_ccw_sch_driver = {
        .drv = {
                .name = "vfio_ccw",
                .owner = THIS_MODULE,
        },
        .subchannel_type = vfio_ccw_sch_ids,
        .irq = vfio_ccw_sch_irq,
        .probe = vfio_ccw_sch_probe,
        .remove = vfio_ccw_sch_remove,
        .shutdown = vfio_ccw_sch_shutdown,
        .sch_event = vfio_ccw_sch_event,
        .chp_event = vfio_ccw_chp_event,
};

static int __init vfio_ccw_debug_init(void)
{
        vfio_ccw_debug_msg_id = debug_register("vfio_ccw_msg", 16, 1,
                                               11 * sizeof(long));
        if (!vfio_ccw_debug_msg_id)
                goto out_unregister;
        debug_register_view(vfio_ccw_debug_msg_id, &debug_sprintf_view);
        debug_set_level(vfio_ccw_debug_msg_id, 2);
        vfio_ccw_debug_trace_id = debug_register("vfio_ccw_trace", 16, 1, 16);
        if (!vfio_ccw_debug_trace_id)
                goto out_unregister;
        debug_register_view(vfio_ccw_debug_trace_id, &debug_hex_ascii_view);
        debug_set_level(vfio_ccw_debug_trace_id, 2);
        return 0;

out_unregister:
        debug_unregister(vfio_ccw_debug_msg_id);
        debug_unregister(vfio_ccw_debug_trace_id);
        return -1;
}

static void vfio_ccw_debug_exit(void)
{
        debug_unregister(vfio_ccw_debug_msg_id);
        debug_unregister(vfio_ccw_debug_trace_id);
}

static void vfio_ccw_destroy_regions(void)
{
        kmem_cache_destroy(vfio_ccw_crw_region);
        kmem_cache_destroy(vfio_ccw_schib_region);
        kmem_cache_destroy(vfio_ccw_cmd_region);
        kmem_cache_destroy(vfio_ccw_io_region);
}

static int __init vfio_ccw_sch_init(void)
{
        int ret;

        ret = vfio_ccw_debug_init();
        if (ret)
                return ret;

        vfio_ccw_work_q = create_singlethread_workqueue("vfio-ccw");
        if (!vfio_ccw_work_q) {
                ret = -ENOMEM;
                goto out_regions;
        }

        vfio_ccw_io_region = kmem_cache_create_usercopy("vfio_ccw_io_region",
                                        sizeof(struct ccw_io_region), 0,
                                        SLAB_ACCOUNT, 0,
                                        sizeof(struct ccw_io_region), NULL);
        if (!vfio_ccw_io_region) {
                ret = -ENOMEM;
                goto out_regions;
        }

        vfio_ccw_cmd_region = kmem_cache_create_usercopy("vfio_ccw_cmd_region",
                                        sizeof(struct ccw_cmd_region), 0,
                                        SLAB_ACCOUNT, 0,
                                        sizeof(struct ccw_cmd_region), NULL);
        if (!vfio_ccw_cmd_region) {
                ret = -ENOMEM;
                goto out_regions;
        }

        vfio_ccw_schib_region = kmem_cache_create_usercopy("vfio_ccw_schib_region",
                                        sizeof(struct ccw_schib_region), 0,
                                        SLAB_ACCOUNT, 0,
                                        sizeof(struct ccw_schib_region), NULL);

        if (!vfio_ccw_schib_region) {
                ret = -ENOMEM;
                goto out_regions;
        }

        vfio_ccw_crw_region = kmem_cache_create_usercopy("vfio_ccw_crw_region",
                                        sizeof(struct ccw_crw_region), 0,
                                        SLAB_ACCOUNT, 0,
                                        sizeof(struct ccw_crw_region), NULL);

        if (!vfio_ccw_crw_region) {
                ret = -ENOMEM;
                goto out_regions;
        }

        ret = mdev_register_driver(&vfio_ccw_mdev_driver);
        if (ret)
                goto out_regions;

        isc_register(VFIO_CCW_ISC);
        ret = css_driver_register(&vfio_ccw_sch_driver);
        if (ret) {
                isc_unregister(VFIO_CCW_ISC);
                goto out_driver;
        }

        return ret;

out_driver:
        mdev_unregister_driver(&vfio_ccw_mdev_driver);
out_regions:
        vfio_ccw_destroy_regions();
        destroy_workqueue(vfio_ccw_work_q);
        vfio_ccw_debug_exit();
        return ret;
}

static void __exit vfio_ccw_sch_exit(void)
{
        css_driver_unregister(&vfio_ccw_sch_driver);
        mdev_unregister_driver(&vfio_ccw_mdev_driver);
        isc_unregister(VFIO_CCW_ISC);
        vfio_ccw_destroy_regions();
        destroy_workqueue(vfio_ccw_work_q);
        vfio_ccw_debug_exit();
}
module_init(vfio_ccw_sch_init);
module_exit(vfio_ccw_sch_exit);

MODULE_DESCRIPTION("VFIO based Subchannel device driver");
MODULE_LICENSE("GPL v2");