// SPDX-License-Identifier: GPL-2.0
/* Copyright(c) 2019 Intel Corporation. All rights rsvd. */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <uapi/linux/idxd.h>
#include "idxd.h"
#include "registers.h"

static struct idxd_desc *__get_desc(struct idxd_wq *wq, int idx, int cpu)
{
        struct idxd_desc *desc;
        struct idxd_device *idxd = wq->idxd;

        desc = wq->descs[idx];
        memset(desc->hw, 0, sizeof(struct dsa_hw_desc));
        memset(desc->completion, 0, idxd->data->compl_size);
        desc->cpu = cpu;

        if (device_pasid_enabled(idxd))
                desc->hw->pasid = idxd->pasid;

        return desc;
}

struct idxd_desc *idxd_alloc_desc(struct idxd_wq *wq, enum idxd_op_type optype)
{
        int cpu, idx;
        struct idxd_device *idxd = wq->idxd;
        DEFINE_SBQ_WAIT(wait);
        struct sbq_wait_state *ws;
        struct sbitmap_queue *sbq;

        if (idxd->state != IDXD_DEV_ENABLED)
                return ERR_PTR(-EIO);

        sbq = &wq->sbq;
        idx = sbitmap_queue_get(sbq, &cpu);
        if (idx < 0) {
                if (optype == IDXD_OP_NONBLOCK)
                        return ERR_PTR(-EAGAIN);
        } else {
                return __get_desc(wq, idx, cpu);
        }

        ws = &sbq->ws[0];
        for (;;) {
                sbitmap_prepare_to_wait(sbq, ws, &wait, TASK_INTERRUPTIBLE);
                if (signal_pending_state(TASK_INTERRUPTIBLE, current))
                        break;
                idx = sbitmap_queue_get(sbq, &cpu);
                if (idx >= 0)
                        break;
                schedule();
        }

        sbitmap_finish_wait(sbq, ws, &wait);
        if (idx < 0)
                return ERR_PTR(-EAGAIN);

        return __get_desc(wq, idx, cpu);
}
EXPORT_SYMBOL_NS_GPL(idxd_alloc_desc, "IDXD");

void idxd_free_desc(struct idxd_wq *wq, struct idxd_desc *desc)
{
        int cpu = desc->cpu;

        desc->cpu = -1;
        sbitmap_queue_clear(&wq->sbq, desc->id, cpu);
}
EXPORT_SYMBOL_NS_GPL(idxd_free_desc, "IDXD");

static struct idxd_desc *list_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
                                         struct idxd_desc *desc)
{
        struct idxd_desc *d, *n;

        lockdep_assert_held(&ie->list_lock);
        list_for_each_entry_safe(d, n, &ie->work_list, list) {
                if (d == desc) {
                        list_del(&d->list);
                        return d;
                }
        }

        /*
         * At this point, the desc needs to be aborted is held by the completion
         * handler where it has taken it off the pending list but has not added to the
         * work list. It will be cleaned up by the interrupt handler when it sees the
         * IDXD_COMP_DESC_ABORT for completion status.
         */
        return NULL;
}

static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
                             struct idxd_desc *desc)
{
        struct idxd_desc *d, *t, *found = NULL;
        struct llist_node *head;
        LIST_HEAD(flist);

        desc->completion->status = IDXD_COMP_DESC_ABORT;
        /*
         * Grab the list lock so it will block the irq thread handler. This allows the
         * abort code to locate the descriptor need to be aborted.
         */
        spin_lock(&ie->list_lock);
        head = llist_del_all(&ie->pending_llist);
        if (head) {
                llist_for_each_entry_safe(d, t, head, llnode) {
                        if (d == desc) {
                                found = desc;
                                continue;
                        }

                        if (d->completion->status)
                                list_add_tail(&d->list, &flist);
                        else
                                list_add_tail(&d->list, &ie->work_list);
                }
        }

        if (!found)
                found = list_abort_desc(wq, ie, desc);
        spin_unlock(&ie->list_lock);

        if (found)
                idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, false,
                                      NULL, NULL);

        /*
         * completing the descriptor will return desc to allocator and
         * the desc can be acquired by a different process and the
         * desc->list can be modified.  Delete desc from list so the
         * list traversing does not get corrupted by the other process.
         */
        list_for_each_entry_safe(d, t, &flist, list) {
                list_del_init(&d->list);
                idxd_dma_complete_txd(d, IDXD_COMPLETE_ABORT, true,
                                      NULL, NULL);
        }
}

/*
 * ENQCMDS typically fail when the WQ is inactive or busy. On host submission, the driver
 * has better control of number of descriptors being submitted to a shared wq by limiting
 * the number of driver allocated descriptors to the wq size. However, when the swq is
 * exported to a guest kernel, it may be shared with multiple guest kernels. This means
 * the likelihood of getting busy returned on the swq when submitting goes significantly up.
 * Having a tunable retry mechanism allows the driver to keep trying for a bit before giving
 * up. The sysfs knob can be tuned by the system administrator.
 */
int idxd_enqcmds(struct idxd_wq *wq, void __iomem *portal, const void *desc)
{
        unsigned int retries = wq->enqcmds_retries;
        int rc;

        do {
                rc = enqcmds(portal, desc);
                if (rc == 0)
                        break;
                cpu_relax();
        } while (retries--);

        return rc;
}

int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
{
        struct idxd_device *idxd = wq->idxd;
        struct idxd_irq_entry *ie = NULL;
        u32 desc_flags = desc->hw->flags;
        void __iomem *portal;
        int rc;

        if (idxd->state != IDXD_DEV_ENABLED)
                return -EIO;

        if (!percpu_ref_tryget_live(&wq->wq_active)) {
                wait_for_completion(&wq->wq_resurrect);
                if (!percpu_ref_tryget_live(&wq->wq_active))
                        return -ENXIO;
        }

        portal = idxd_wq_portal_addr(wq);

        /*
         * Pending the descriptor to the lockless list for the irq_entry
         * that we designated the descriptor to.
         */
        if (desc_flags & IDXD_OP_FLAG_RCI) {
                ie = &wq->ie;
                desc->hw->int_handle = ie->int_handle;
                llist_add(&desc->llnode, &ie->pending_llist);
        }

        /*
         * The wmb() flushes writes to coherent DMA data before
         * possibly triggering a DMA read. The wmb() is necessary
         * even on UP because the recipient is a device.
         */
        wmb();

        if (wq_dedicated(wq)) {
                iosubmit_cmds512(portal, desc->hw, 1);
        } else {
                rc = idxd_enqcmds(wq, portal, desc->hw);
                if (rc < 0) {
                        percpu_ref_put(&wq->wq_active);
                        /* abort operation frees the descriptor */
                        if (ie)
                                llist_abort_desc(wq, ie, desc);
                        return rc;
                }
        }

        percpu_ref_put(&wq->wq_active);
        return 0;
}
EXPORT_SYMBOL_NS_GPL(idxd_submit_desc, "IDXD");