// SPDX-License-Identifier: (GPL-2.0 OR MIT)
/* Google virtual Ethernet (gve) driver
 *
 * Copyright (C) 2015-2021 Google, Inc.
 */

#include "gve.h"
#include "gve_adminq.h"
#include "gve_utils.h"
#include <linux/etherdevice.h>

static void gve_rx_free_buffer(struct device *dev,
                               struct gve_rx_slot_page_info *page_info,
                               union gve_rx_data_slot *data_slot)
{
        dma_addr_t dma = (dma_addr_t)(be64_to_cpu(data_slot->addr) &
                                      GVE_DATA_SLOT_ADDR_PAGE_MASK);

        gve_free_page(dev, page_info->page, dma, DMA_FROM_DEVICE);
}

static void gve_rx_unfill_pages(struct gve_priv *priv, struct gve_rx_ring *rx)
{
        if (rx->data.raw_addressing) {
                u32 slots = rx->mask + 1;
                int i;

                for (i = 0; i < slots; i++)
                        gve_rx_free_buffer(&priv->pdev->dev, &rx->data.page_info[i],
                                           &rx->data.data_ring[i]);
        } else {
                gve_unassign_qpl(priv, rx->data.qpl->id);
                rx->data.qpl = NULL;
        }
        kvfree(rx->data.page_info);
        rx->data.page_info = NULL;
}

static void gve_rx_free_ring(struct gve_priv *priv, int idx)
{
        struct gve_rx_ring *rx = &priv->rx[idx];
        struct device *dev = &priv->pdev->dev;
        u32 slots = rx->mask + 1;
        size_t bytes;

        gve_rx_remove_from_block(priv, idx);

        bytes = sizeof(struct gve_rx_desc) * priv->rx_desc_cnt;
        dma_free_coherent(dev, bytes, rx->desc.desc_ring, rx->desc.bus);
        rx->desc.desc_ring = NULL;

        dma_free_coherent(dev, sizeof(*rx->q_resources),
                          rx->q_resources, rx->q_resources_bus);
        rx->q_resources = NULL;

        gve_rx_unfill_pages(priv, rx);

        bytes = sizeof(*rx->data.data_ring) * slots;
        dma_free_coherent(dev, bytes, rx->data.data_ring,
                          rx->data.data_bus);
        rx->data.data_ring = NULL;
        netif_dbg(priv, drv, priv->dev, "freed rx ring %d\n", idx);
}

static void gve_setup_rx_buffer(struct gve_rx_slot_page_info *page_info,
                             dma_addr_t addr, struct page *page, __be64 *slot_addr)
{
        page_info->page = page;
        page_info->page_offset = 0;
        page_info->page_address = page_address(page);
        *slot_addr = cpu_to_be64(addr);
}

static int gve_rx_alloc_buffer(struct gve_priv *priv, struct device *dev,
                               struct gve_rx_slot_page_info *page_info,
                               union gve_rx_data_slot *data_slot)
{
        struct page *page;
        dma_addr_t dma;
        int err;

        err = gve_alloc_page(priv, dev, &page, &dma, DMA_FROM_DEVICE);
        if (err)
                return err;

        gve_setup_rx_buffer(page_info, dma, page, &data_slot->addr);
        return 0;
}

static int gve_prefill_rx_pages(struct gve_rx_ring *rx)
{
        struct gve_priv *priv = rx->gve;
        u32 slots;
        int err;
        int i;

        /* Allocate one page per Rx queue slot. Each page is split into two
         * packet buffers, when possible we "page flip" between the two.
         */
        slots = rx->mask + 1;

        rx->data.page_info = kvzalloc(slots *
                                      sizeof(*rx->data.page_info), GFP_KERNEL);
        if (!rx->data.page_info)
                return -ENOMEM;

        if (!rx->data.raw_addressing) {
                rx->data.qpl = gve_assign_rx_qpl(priv);
                if (!rx->data.qpl) {
                        kvfree(rx->data.page_info);
                        rx->data.page_info = NULL;
                        return -ENOMEM;
                }
        }
        for (i = 0; i < slots; i++) {
                if (!rx->data.raw_addressing) {
                        struct page *page = rx->data.qpl->pages[i];
                        dma_addr_t addr = i * PAGE_SIZE;

                        gve_setup_rx_buffer(&rx->data.page_info[i], addr, page,
                                            &rx->data.data_ring[i].qpl_offset);
                        continue;
                }
                err = gve_rx_alloc_buffer(priv, &priv->pdev->dev, &rx->data.page_info[i],
                                          &rx->data.data_ring[i]);
                if (err)
                        goto alloc_err;
        }

        return slots;
alloc_err:
        while (i--)
                gve_rx_free_buffer(&priv->pdev->dev,
                                   &rx->data.page_info[i],
                                   &rx->data.data_ring[i]);
        return err;
}

static int gve_rx_alloc_ring(struct gve_priv *priv, int idx)
{
        struct gve_rx_ring *rx = &priv->rx[idx];
        struct device *hdev = &priv->pdev->dev;
        u32 slots, npages;
        int filled_pages;
        size_t bytes;
        int err;

        netif_dbg(priv, drv, priv->dev, "allocating rx ring\n");
        /* Make sure everything is zeroed to start with */
        memset(rx, 0, sizeof(*rx));

        rx->gve = priv;
        rx->q_num = idx;

        slots = priv->rx_data_slot_cnt;
        rx->mask = slots - 1;
        rx->data.raw_addressing = priv->queue_format == GVE_GQI_RDA_FORMAT;

        /* alloc rx data ring */
        bytes = sizeof(*rx->data.data_ring) * slots;
        rx->data.data_ring = dma_alloc_coherent(hdev, bytes,
                                                &rx->data.data_bus,
                                                GFP_KERNEL);
        if (!rx->data.data_ring)
                return -ENOMEM;
        filled_pages = gve_prefill_rx_pages(rx);
        if (filled_pages < 0) {
                err = -ENOMEM;
                goto abort_with_slots;
        }
        rx->fill_cnt = filled_pages;
        /* Ensure data ring slots (packet buffers) are visible. */
        dma_wmb();

        /* Alloc gve_queue_resources */
        rx->q_resources =
                dma_alloc_coherent(hdev,
                                   sizeof(*rx->q_resources),
                                   &rx->q_resources_bus,
                                   GFP_KERNEL);
        if (!rx->q_resources) {
                err = -ENOMEM;
                goto abort_filled;
        }
        netif_dbg(priv, drv, priv->dev, "rx[%d]->data.data_bus=%lx\n", idx,
                  (unsigned long)rx->data.data_bus);

        /* alloc rx desc ring */
        bytes = sizeof(struct gve_rx_desc) * priv->rx_desc_cnt;
        npages = bytes / PAGE_SIZE;
        if (npages * PAGE_SIZE != bytes) {
                err = -EIO;
                goto abort_with_q_resources;
        }

        rx->desc.desc_ring = dma_alloc_coherent(hdev, bytes, &rx->desc.bus,
                                                GFP_KERNEL);
        if (!rx->desc.desc_ring) {
                err = -ENOMEM;
                goto abort_with_q_resources;
        }
        rx->cnt = 0;
        rx->db_threshold = priv->rx_desc_cnt / 2;
        rx->desc.seqno = 1;
        gve_rx_add_to_block(priv, idx);

        return 0;

abort_with_q_resources:
        dma_free_coherent(hdev, sizeof(*rx->q_resources),
                          rx->q_resources, rx->q_resources_bus);
        rx->q_resources = NULL;
abort_filled:
        gve_rx_unfill_pages(priv, rx);
abort_with_slots:
        bytes = sizeof(*rx->data.data_ring) * slots;
        dma_free_coherent(hdev, bytes, rx->data.data_ring, rx->data.data_bus);
        rx->data.data_ring = NULL;

        return err;
}

int gve_rx_alloc_rings(struct gve_priv *priv)
{
        int err = 0;
        int i;

        for (i = 0; i < priv->rx_cfg.num_queues; i++) {
                err = gve_rx_alloc_ring(priv, i);
                if (err) {
                        netif_err(priv, drv, priv->dev,
                                  "Failed to alloc rx ring=%d: err=%d\n",
                                  i, err);
                        break;
                }
        }
        /* Unallocate if there was an error */
        if (err) {
                int j;

                for (j = 0; j < i; j++)
                        gve_rx_free_ring(priv, j);
        }
        return err;
}

void gve_rx_free_rings_gqi(struct gve_priv *priv)
{
        int i;

        for (i = 0; i < priv->rx_cfg.num_queues; i++)
                gve_rx_free_ring(priv, i);
}

void gve_rx_write_doorbell(struct gve_priv *priv, struct gve_rx_ring *rx)
{
        u32 db_idx = be32_to_cpu(rx->q_resources->db_index);

        iowrite32be(rx->fill_cnt, &priv->db_bar2[db_idx]);
}

static enum pkt_hash_types gve_rss_type(__be16 pkt_flags)
{
        if (likely(pkt_flags & (GVE_RXF_TCP | GVE_RXF_UDP)))
                return PKT_HASH_TYPE_L4;
        if (pkt_flags & (GVE_RXF_IPV4 | GVE_RXF_IPV6))
                return PKT_HASH_TYPE_L3;
        return PKT_HASH_TYPE_L2;
}

static struct sk_buff *gve_rx_add_frags(struct napi_struct *napi,
                                        struct gve_rx_slot_page_info *page_info,
                                        u16 len)
{
        struct sk_buff *skb = napi_get_frags(napi);

        if (unlikely(!skb))
                return NULL;

        skb_add_rx_frag(skb, 0, page_info->page,
                        page_info->page_offset +
                        GVE_RX_PAD, len, PAGE_SIZE / 2);

        return skb;
}

static void gve_rx_flip_buff(struct gve_rx_slot_page_info *page_info, __be64 *slot_addr)
{
        const __be64 offset = cpu_to_be64(PAGE_SIZE / 2);

        /* "flip" to other packet buffer on this page */
        page_info->page_offset ^= PAGE_SIZE / 2;
        *(slot_addr) ^= offset;
}

static bool gve_rx_can_flip_buffers(struct net_device *netdev)
{
        return PAGE_SIZE == 4096
                ? netdev->mtu + GVE_RX_PAD + ETH_HLEN <= PAGE_SIZE / 2 : false;
}

static int gve_rx_can_recycle_buffer(struct page *page)
{
        int pagecount = page_count(page);

        /* This page is not being used by any SKBs - reuse */
        if (pagecount == 1)
                return 1;
        /* This page is still being used by an SKB - we can't reuse */
        else if (pagecount >= 2)
                return 0;
        WARN(pagecount < 1, "Pagecount should never be < 1");
        return -1;
}

static struct sk_buff *
gve_rx_raw_addressing(struct device *dev, struct net_device *netdev,
                      struct gve_rx_slot_page_info *page_info, u16 len,
                      struct napi_struct *napi,
                      union gve_rx_data_slot *data_slot)
{
        struct sk_buff *skb;

        skb = gve_rx_add_frags(napi, page_info, len);
        if (!skb)
                return NULL;

        /* Optimistically stop the kernel from freeing the page by increasing
         * the page bias. We will check the refcount in refill to determine if
         * we need to alloc a new page.
         */
        get_page(page_info->page);

        return skb;
}

static struct sk_buff *
gve_rx_qpl(struct device *dev, struct net_device *netdev,
           struct gve_rx_ring *rx, struct gve_rx_slot_page_info *page_info,
           u16 len, struct napi_struct *napi,
           union gve_rx_data_slot *data_slot)
{
        struct sk_buff *skb;

        /* if raw_addressing mode is not enabled gvnic can only receive into
         * registered segments. If the buffer can't be recycled, our only
         * choice is to copy the data out of it so that we can return it to the
         * device.
         */
        if (page_info->can_flip) {
                skb = gve_rx_add_frags(napi, page_info, len);
                /* No point in recycling if we didn't get the skb */
                if (skb) {
                        /* Make sure that the page isn't freed. */
                        get_page(page_info->page);
                        gve_rx_flip_buff(page_info, &data_slot->qpl_offset);
                }
        } else {
                skb = gve_rx_copy(netdev, napi, page_info, len, GVE_RX_PAD);
                if (skb) {
                        u64_stats_update_begin(&rx->statss);
                        rx->rx_copied_pkt++;
                        u64_stats_update_end(&rx->statss);
                }
        }
        return skb;
}

static bool gve_rx(struct gve_rx_ring *rx, struct gve_rx_desc *rx_desc,
                   netdev_features_t feat, u32 idx)
{
        struct gve_rx_slot_page_info *page_info;
        struct gve_priv *priv = rx->gve;
        struct napi_struct *napi = &priv->ntfy_blocks[rx->ntfy_id].napi;
        struct net_device *dev = priv->dev;
        union gve_rx_data_slot *data_slot;
        struct sk_buff *skb = NULL;
        dma_addr_t page_bus;
        u16 len;

        /* drop this packet */
        if (unlikely(rx_desc->flags_seq & GVE_RXF_ERR)) {
                u64_stats_update_begin(&rx->statss);
                rx->rx_desc_err_dropped_pkt++;
                u64_stats_update_end(&rx->statss);
                return false;
        }

        len = be16_to_cpu(rx_desc->len) - GVE_RX_PAD;
        page_info = &rx->data.page_info[idx];

        data_slot = &rx->data.data_ring[idx];
        page_bus = (rx->data.raw_addressing) ?
                        be64_to_cpu(data_slot->addr) & GVE_DATA_SLOT_ADDR_PAGE_MASK :
                        rx->data.qpl->page_buses[idx];
        dma_sync_single_for_cpu(&priv->pdev->dev, page_bus,
                                PAGE_SIZE, DMA_FROM_DEVICE);

        if (len <= priv->rx_copybreak) {
                /* Just copy small packets */
                skb = gve_rx_copy(dev, napi, page_info, len, GVE_RX_PAD);
                u64_stats_update_begin(&rx->statss);
                rx->rx_copied_pkt++;
                rx->rx_copybreak_pkt++;
                u64_stats_update_end(&rx->statss);
        } else {
                u8 can_flip = gve_rx_can_flip_buffers(dev);
                int recycle = 0;

                if (can_flip) {
                        recycle = gve_rx_can_recycle_buffer(page_info->page);
                        if (recycle < 0) {
                                if (!rx->data.raw_addressing)
                                        gve_schedule_reset(priv);
                                return false;
                        }
                }

                page_info->can_flip = can_flip && recycle;
                if (rx->data.raw_addressing) {
                        skb = gve_rx_raw_addressing(&priv->pdev->dev, dev,
                                                    page_info, len, napi,
                                                    data_slot);
                } else {
                        skb = gve_rx_qpl(&priv->pdev->dev, dev, rx,
                                         page_info, len, napi, data_slot);
                }
        }

        if (!skb) {
                u64_stats_update_begin(&rx->statss);
                rx->rx_skb_alloc_fail++;
                u64_stats_update_end(&rx->statss);
                return false;
        }

        if (likely(feat & NETIF_F_RXCSUM)) {
                /* NIC passes up the partial sum */
                if (rx_desc->csum)
                        skb->ip_summed = CHECKSUM_COMPLETE;
                else
                        skb->ip_summed = CHECKSUM_NONE;
                skb->csum = csum_unfold(rx_desc->csum);
        }

        /* parse flags & pass relevant info up */
        if (likely(feat & NETIF_F_RXHASH) &&
            gve_needs_rss(rx_desc->flags_seq))
                skb_set_hash(skb, be32_to_cpu(rx_desc->rss_hash),
                             gve_rss_type(rx_desc->flags_seq));

        if (skb_is_nonlinear(skb))
                napi_gro_frags(napi);
        else
                napi_gro_receive(napi, skb);
        return true;
}

static bool gve_rx_work_pending(struct gve_rx_ring *rx)
{
        struct gve_rx_desc *desc;
        __be16 flags_seq;
        u32 next_idx;

        next_idx = rx->cnt & rx->mask;
        desc = rx->desc.desc_ring + next_idx;

        flags_seq = desc->flags_seq;
        /* Make sure we have synchronized the seq no with the device */
        smp_rmb();

        return (GVE_SEQNO(flags_seq) == rx->desc.seqno);
}

static bool gve_rx_refill_buffers(struct gve_priv *priv, struct gve_rx_ring *rx)
{
        int refill_target = rx->mask + 1;
        u32 fill_cnt = rx->fill_cnt;

        while (fill_cnt - rx->cnt < refill_target) {
                struct gve_rx_slot_page_info *page_info;
                u32 idx = fill_cnt & rx->mask;

                page_info = &rx->data.page_info[idx];
                if (page_info->can_flip) {
                        /* The other half of the page is free because it was
                         * free when we processed the descriptor. Flip to it.
                         */
                        union gve_rx_data_slot *data_slot =
                                                &rx->data.data_ring[idx];

                        gve_rx_flip_buff(page_info, &data_slot->addr);
                        page_info->can_flip = 0;
                } else {
                        /* It is possible that the networking stack has already
                         * finished processing all outstanding packets in the buffer
                         * and it can be reused.
                         * Flipping is unnecessary here - if the networking stack still
                         * owns half the page it is impossible to tell which half. Either
                         * the whole page is free or it needs to be replaced.
                         */
                        int recycle = gve_rx_can_recycle_buffer(page_info->page);

                        if (recycle < 0) {
                                if (!rx->data.raw_addressing)
                                        gve_schedule_reset(priv);
                                return false;
                        }
                        if (!recycle) {
                                /* We can't reuse the buffer - alloc a new one*/
                                union gve_rx_data_slot *data_slot =
                                                &rx->data.data_ring[idx];
                                struct device *dev = &priv->pdev->dev;

                                gve_rx_free_buffer(dev, page_info, data_slot);
                                page_info->page = NULL;
                                if (gve_rx_alloc_buffer(priv, dev, page_info, data_slot))
                                        break;
                        }
                }
                fill_cnt++;
        }
        rx->fill_cnt = fill_cnt;
        return true;
}

bool gve_clean_rx_done(struct gve_rx_ring *rx, int budget,
                       netdev_features_t feat)
{
        struct gve_priv *priv = rx->gve;
        u32 work_done = 0, packets = 0;
        struct gve_rx_desc *desc;
        u32 cnt = rx->cnt;
        u32 idx = cnt & rx->mask;
        u64 bytes = 0;

        desc = rx->desc.desc_ring + idx;
        while ((GVE_SEQNO(desc->flags_seq) == rx->desc.seqno) &&
               work_done < budget) {
                bool dropped;

                netif_info(priv, rx_status, priv->dev,
                           "[%d] idx=%d desc=%p desc->flags_seq=0x%x\n",
                           rx->q_num, idx, desc, desc->flags_seq);
                netif_info(priv, rx_status, priv->dev,
                           "[%d] seqno=%d rx->desc.seqno=%d\n",
                           rx->q_num, GVE_SEQNO(desc->flags_seq),
                           rx->desc.seqno);
                dropped = !gve_rx(rx, desc, feat, idx);
                if (!dropped) {
                        bytes += be16_to_cpu(desc->len) - GVE_RX_PAD;
                        packets++;
                }
                cnt++;
                idx = cnt & rx->mask;
                desc = rx->desc.desc_ring + idx;
                rx->desc.seqno = gve_next_seqno(rx->desc.seqno);
                work_done++;
        }

        if (!work_done && rx->fill_cnt - cnt > rx->db_threshold)
                return false;

        u64_stats_update_begin(&rx->statss);
        rx->rpackets += packets;
        rx->rbytes += bytes;
        u64_stats_update_end(&rx->statss);
        rx->cnt = cnt;

        /* restock ring slots */
        if (!rx->data.raw_addressing) {
                /* In QPL mode buffs are refilled as the desc are processed */
                rx->fill_cnt += work_done;
        } else if (rx->fill_cnt - cnt <= rx->db_threshold) {
                /* In raw addressing mode buffs are only refilled if the avail
                 * falls below a threshold.
                 */
                if (!gve_rx_refill_buffers(priv, rx))
                        return false;

                /* If we were not able to completely refill buffers, we'll want
                 * to schedule this queue for work again to refill buffers.
                 */
                if (rx->fill_cnt - cnt <= rx->db_threshold) {
                        gve_rx_write_doorbell(priv, rx);
                        return true;
                }
        }

        gve_rx_write_doorbell(priv, rx);
        return gve_rx_work_pending(rx);
}

bool gve_rx_poll(struct gve_notify_block *block, int budget)
{
        struct gve_rx_ring *rx = block->rx;
        netdev_features_t feat;
        bool repoll = false;

        feat = block->napi.dev->features;

        /* If budget is 0, do all the work */
        if (budget == 0)
                budget = INT_MAX;

        if (budget > 0)
                repoll |= gve_clean_rx_done(rx, budget, feat);
        else
                repoll |= gve_rx_work_pending(rx);
        return repoll;
}