/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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/>.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/if_ether.h>
#include <linux/vmalloc.h>
#include <linux/rtnetlink.h>
#include <linux/prefetch.h>

#include <asm/sync_bitops.h>

#include "hyperv_net.h"

/*
 * Switch the data path from the synthetic interface to the VF
 * interface.
 */
void netvsc_switch_datapath(struct net_device *ndev, bool vf)
{
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        struct hv_device *dev = net_device_ctx->device_ctx;
        struct netvsc_device *nv_dev = rtnl_dereference(net_device_ctx->nvdev);
        struct nvsp_message *init_pkt = &nv_dev->channel_init_pkt;

        memset(init_pkt, 0, sizeof(struct nvsp_message));
        init_pkt->hdr.msg_type = NVSP_MSG4_TYPE_SWITCH_DATA_PATH;
        if (vf)
                init_pkt->msg.v4_msg.active_dp.active_datapath =
                        NVSP_DATAPATH_VF;
        else
                init_pkt->msg.v4_msg.active_dp.active_datapath =
                        NVSP_DATAPATH_SYNTHETIC;

        vmbus_sendpacket(dev->channel, init_pkt,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_pkt,
                               VM_PKT_DATA_INBAND, 0);
}

static struct netvsc_device *alloc_net_device(void)
{
        struct netvsc_device *net_device;

        net_device = kzalloc(sizeof(struct netvsc_device), GFP_KERNEL);
        if (!net_device)
                return NULL;

        init_waitqueue_head(&net_device->wait_drain);
        net_device->destroy = false;
        atomic_set(&net_device->open_cnt, 0);
        net_device->max_pkt = RNDIS_MAX_PKT_DEFAULT;
        net_device->pkt_align = RNDIS_PKT_ALIGN_DEFAULT;

        init_completion(&net_device->channel_init_wait);
        init_waitqueue_head(&net_device->subchan_open);
        INIT_WORK(&net_device->subchan_work, rndis_set_subchannel);

        return net_device;
}

static void free_netvsc_device(struct rcu_head *head)
{
        struct netvsc_device *nvdev
                = container_of(head, struct netvsc_device, rcu);
        int i;

        for (i = 0; i < VRSS_CHANNEL_MAX; i++)
                vfree(nvdev->chan_table[i].mrc.slots);

        kfree(nvdev);
}

static void free_netvsc_device_rcu(struct netvsc_device *nvdev)
{
        call_rcu(&nvdev->rcu, free_netvsc_device);
}

static void netvsc_destroy_buf(struct hv_device *device)
{
        struct nvsp_message *revoke_packet;
        struct net_device *ndev = hv_get_drvdata(device);
        struct net_device_context *ndc = netdev_priv(ndev);
        struct netvsc_device *net_device = rtnl_dereference(ndc->nvdev);
        int ret;

        /*
         * If we got a section count, it means we received a
         * SendReceiveBufferComplete msg (ie sent
         * NvspMessage1TypeSendReceiveBuffer msg) therefore, we need
         * to send a revoke msg here
         */
        if (net_device->recv_section_cnt) {
                /* Send the revoke receive buffer */
                revoke_packet = &net_device->revoke_packet;
                memset(revoke_packet, 0, sizeof(struct nvsp_message));

                revoke_packet->hdr.msg_type =
                        NVSP_MSG1_TYPE_REVOKE_RECV_BUF;
                revoke_packet->msg.v1_msg.
                revoke_recv_buf.id = NETVSC_RECEIVE_BUFFER_ID;

                ret = vmbus_sendpacket(device->channel,
                                       revoke_packet,
                                       sizeof(struct nvsp_message),
                                       (unsigned long)revoke_packet,
                                       VM_PKT_DATA_INBAND, 0);
                /* If the failure is because the channel is rescinded;
                 * ignore the failure since we cannot send on a rescinded
                 * channel. This would allow us to properly cleanup
                 * even when the channel is rescinded.
                 */
                if (device->channel->rescind)
                        ret = 0;
                /*
                 * If we failed here, we might as well return and
                 * have a leak rather than continue and a bugchk
                 */
                if (ret != 0) {
                        netdev_err(ndev, "unable to send "
                                "revoke receive buffer to netvsp\n");
                        return;
                }
                net_device->recv_section_cnt = 0;
        }

        /* Teardown the gpadl on the vsp end */
        if (net_device->recv_buf_gpadl_handle) {
                ret = vmbus_teardown_gpadl(device->channel,
                                           net_device->recv_buf_gpadl_handle);

                /* If we failed here, we might as well return and have a leak
                 * rather than continue and a bugchk
                 */
                if (ret != 0) {
                        netdev_err(ndev,
                                   "unable to teardown receive buffer's gpadl\n");
                        return;
                }
                net_device->recv_buf_gpadl_handle = 0;
        }

        if (net_device->recv_buf) {
                /* Free up the receive buffer */
                vfree(net_device->recv_buf);
                net_device->recv_buf = NULL;
        }

        /* Deal with the send buffer we may have setup.
         * If we got a  send section size, it means we received a
         * NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE msg (ie sent
         * NVSP_MSG1_TYPE_SEND_SEND_BUF msg) therefore, we need
         * to send a revoke msg here
         */
        if (net_device->send_section_cnt) {
                /* Send the revoke receive buffer */
                revoke_packet = &net_device->revoke_packet;
                memset(revoke_packet, 0, sizeof(struct nvsp_message));

                revoke_packet->hdr.msg_type =
                        NVSP_MSG1_TYPE_REVOKE_SEND_BUF;
                revoke_packet->msg.v1_msg.revoke_send_buf.id =
                        NETVSC_SEND_BUFFER_ID;

                ret = vmbus_sendpacket(device->channel,
                                       revoke_packet,
                                       sizeof(struct nvsp_message),
                                       (unsigned long)revoke_packet,
                                       VM_PKT_DATA_INBAND, 0);

                /* If the failure is because the channel is rescinded;
                 * ignore the failure since we cannot send on a rescinded
                 * channel. This would allow us to properly cleanup
                 * even when the channel is rescinded.
                 */
                if (device->channel->rescind)
                        ret = 0;

                /* If we failed here, we might as well return and
                 * have a leak rather than continue and a bugchk
                 */
                if (ret != 0) {
                        netdev_err(ndev, "unable to send "
                                   "revoke send buffer to netvsp\n");
                        return;
                }
                net_device->send_section_cnt = 0;
        }
        /* Teardown the gpadl on the vsp end */
        if (net_device->send_buf_gpadl_handle) {
                ret = vmbus_teardown_gpadl(device->channel,
                                           net_device->send_buf_gpadl_handle);

                /* If we failed here, we might as well return and have a leak
                 * rather than continue and a bugchk
                 */
                if (ret != 0) {
                        netdev_err(ndev,
                                   "unable to teardown send buffer's gpadl\n");
                        return;
                }
                net_device->send_buf_gpadl_handle = 0;
        }
        if (net_device->send_buf) {
                /* Free up the send buffer */
                vfree(net_device->send_buf);
                net_device->send_buf = NULL;
        }
        kfree(net_device->send_section_map);
}

int netvsc_alloc_recv_comp_ring(struct netvsc_device *net_device, u32 q_idx)
{
        struct netvsc_channel *nvchan = &net_device->chan_table[q_idx];
        int node = cpu_to_node(nvchan->channel->target_cpu);
        size_t size;

        size = net_device->recv_completion_cnt * sizeof(struct recv_comp_data);
        nvchan->mrc.slots = vzalloc_node(size, node);
        if (!nvchan->mrc.slots)
                nvchan->mrc.slots = vzalloc(size);

        return nvchan->mrc.slots ? 0 : -ENOMEM;
}

static int netvsc_init_buf(struct hv_device *device,
                           struct netvsc_device *net_device,
                           const struct netvsc_device_info *device_info)
{
        struct nvsp_1_message_send_receive_buffer_complete *resp;
        struct net_device *ndev = hv_get_drvdata(device);
        struct nvsp_message *init_packet;
        unsigned int buf_size;
        size_t map_words;
        int ret = 0;

        /* Get receive buffer area. */
        buf_size = device_info->recv_sections * device_info->recv_section_size;
        buf_size = roundup(buf_size, PAGE_SIZE);

        net_device->recv_buf = vzalloc(buf_size);
        if (!net_device->recv_buf) {
                netdev_err(ndev,
                           "unable to allocate receive buffer of size %u\n",
                           buf_size);
                ret = -ENOMEM;
                goto cleanup;
        }

        /*
         * Establish the gpadl handle for this buffer on this
         * channel.  Note: This call uses the vmbus connection rather
         * than the channel to establish the gpadl handle.
         */
        ret = vmbus_establish_gpadl(device->channel, net_device->recv_buf,
                                    buf_size,
                                    &net_device->recv_buf_gpadl_handle);
        if (ret != 0) {
                netdev_err(ndev,
                        "unable to establish receive buffer's gpadl\n");
                goto cleanup;
        }

        /* Notify the NetVsp of the gpadl handle */
        init_packet = &net_device->channel_init_pkt;
        memset(init_packet, 0, sizeof(struct nvsp_message));
        init_packet->hdr.msg_type = NVSP_MSG1_TYPE_SEND_RECV_BUF;
        init_packet->msg.v1_msg.send_recv_buf.
                gpadl_handle = net_device->recv_buf_gpadl_handle;
        init_packet->msg.v1_msg.
                send_recv_buf.id = NETVSC_RECEIVE_BUFFER_ID;

        /* Send the gpadl notification request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0) {
                netdev_err(ndev,
                        "unable to send receive buffer's gpadl to netvsp\n");
                goto cleanup;
        }

        wait_for_completion(&net_device->channel_init_wait);

        /* Check the response */
        resp = &init_packet->msg.v1_msg.send_recv_buf_complete;
        if (resp->status != NVSP_STAT_SUCCESS) {
                netdev_err(ndev,
                           "Unable to complete receive buffer initialization with NetVsp - status %d\n",
                           resp->status);
                ret = -EINVAL;
                goto cleanup;
        }

        /* Parse the response */
        netdev_dbg(ndev, "Receive sections: %u sub_allocs: size %u count: %u\n",
                   resp->num_sections, resp->sections[0].sub_alloc_size,
                   resp->sections[0].num_sub_allocs);

        /* There should only be one section for the entire receive buffer */
        if (resp->num_sections != 1 || resp->sections[0].offset != 0) {
                ret = -EINVAL;
                goto cleanup;
        }

        net_device->recv_section_size = resp->sections[0].sub_alloc_size;
        net_device->recv_section_cnt = resp->sections[0].num_sub_allocs;

        /* Setup receive completion ring */
        net_device->recv_completion_cnt
                = round_up(net_device->recv_section_cnt + 1,
                           PAGE_SIZE / sizeof(u64));
        ret = netvsc_alloc_recv_comp_ring(net_device, 0);
        if (ret)
                goto cleanup;

        /* Now setup the send buffer. */
        buf_size = device_info->send_sections * device_info->send_section_size;
        buf_size = round_up(buf_size, PAGE_SIZE);

        net_device->send_buf = vzalloc(buf_size);
        if (!net_device->send_buf) {
                netdev_err(ndev, "unable to allocate send buffer of size %u\n",
                           buf_size);
                ret = -ENOMEM;
                goto cleanup;
        }

        /* Establish the gpadl handle for this buffer on this
         * channel.  Note: This call uses the vmbus connection rather
         * than the channel to establish the gpadl handle.
         */
        ret = vmbus_establish_gpadl(device->channel, net_device->send_buf,
                                    buf_size,
                                    &net_device->send_buf_gpadl_handle);
        if (ret != 0) {
                netdev_err(ndev,
                           "unable to establish send buffer's gpadl\n");
                goto cleanup;
        }

        /* Notify the NetVsp of the gpadl handle */
        init_packet = &net_device->channel_init_pkt;
        memset(init_packet, 0, sizeof(struct nvsp_message));
        init_packet->hdr.msg_type = NVSP_MSG1_TYPE_SEND_SEND_BUF;
        init_packet->msg.v1_msg.send_send_buf.gpadl_handle =
                net_device->send_buf_gpadl_handle;
        init_packet->msg.v1_msg.send_send_buf.id = NETVSC_SEND_BUFFER_ID;

        /* Send the gpadl notification request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0) {
                netdev_err(ndev,
                           "unable to send send buffer's gpadl to netvsp\n");
                goto cleanup;
        }

        wait_for_completion(&net_device->channel_init_wait);

        /* Check the response */
        if (init_packet->msg.v1_msg.
            send_send_buf_complete.status != NVSP_STAT_SUCCESS) {
                netdev_err(ndev, "Unable to complete send buffer "
                           "initialization with NetVsp - status %d\n",
                           init_packet->msg.v1_msg.
                           send_send_buf_complete.status);
                ret = -EINVAL;
                goto cleanup;
        }

        /* Parse the response */
        net_device->send_section_size = init_packet->msg.
                                v1_msg.send_send_buf_complete.section_size;

        /* Section count is simply the size divided by the section size. */
        net_device->send_section_cnt = buf_size / net_device->send_section_size;

        netdev_dbg(ndev, "Send section size: %d, Section count:%d\n",
                   net_device->send_section_size, net_device->send_section_cnt);

        /* Setup state for managing the send buffer. */
        map_words = DIV_ROUND_UP(net_device->send_section_cnt, BITS_PER_LONG);

        net_device->send_section_map = kcalloc(map_words, sizeof(ulong), GFP_KERNEL);
        if (net_device->send_section_map == NULL) {
                ret = -ENOMEM;
                goto cleanup;
        }

        goto exit;

cleanup:
        netvsc_destroy_buf(device);

exit:
        return ret;
}

/* Negotiate NVSP protocol version */
static int negotiate_nvsp_ver(struct hv_device *device,
                              struct netvsc_device *net_device,
                              struct nvsp_message *init_packet,
                              u32 nvsp_ver)
{
        struct net_device *ndev = hv_get_drvdata(device);
        int ret;

        memset(init_packet, 0, sizeof(struct nvsp_message));
        init_packet->hdr.msg_type = NVSP_MSG_TYPE_INIT;
        init_packet->msg.init_msg.init.min_protocol_ver = nvsp_ver;
        init_packet->msg.init_msg.init.max_protocol_ver = nvsp_ver;

        /* Send the init request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                               sizeof(struct nvsp_message),
                               (unsigned long)init_packet,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                return ret;

        wait_for_completion(&net_device->channel_init_wait);

        if (init_packet->msg.init_msg.init_complete.status !=
            NVSP_STAT_SUCCESS)
                return -EINVAL;

        if (nvsp_ver == NVSP_PROTOCOL_VERSION_1)
                return 0;

        /* NVSPv2 or later: Send NDIS config */
        memset(init_packet, 0, sizeof(struct nvsp_message));
        init_packet->hdr.msg_type = NVSP_MSG2_TYPE_SEND_NDIS_CONFIG;
        init_packet->msg.v2_msg.send_ndis_config.mtu = ndev->mtu + ETH_HLEN;
        init_packet->msg.v2_msg.send_ndis_config.capability.ieee8021q = 1;

        if (nvsp_ver >= NVSP_PROTOCOL_VERSION_5) {
                init_packet->msg.v2_msg.send_ndis_config.capability.sriov = 1;

                /* Teaming bit is needed to receive link speed updates */
                init_packet->msg.v2_msg.send_ndis_config.capability.teaming = 1;
        }

        ret = vmbus_sendpacket(device->channel, init_packet,
                                sizeof(struct nvsp_message),
                                (unsigned long)init_packet,
                                VM_PKT_DATA_INBAND, 0);

        return ret;
}

static int netvsc_connect_vsp(struct hv_device *device,
                              struct netvsc_device *net_device,
                              const struct netvsc_device_info *device_info)
{
        const u32 ver_list[] = {
                NVSP_PROTOCOL_VERSION_1, NVSP_PROTOCOL_VERSION_2,
                NVSP_PROTOCOL_VERSION_4, NVSP_PROTOCOL_VERSION_5
        };
        struct nvsp_message *init_packet;
        int ndis_version, i, ret;

        init_packet = &net_device->channel_init_pkt;

        /* Negotiate the latest NVSP protocol supported */
        for (i = ARRAY_SIZE(ver_list) - 1; i >= 0; i--)
                if (negotiate_nvsp_ver(device, net_device, init_packet,
                                       ver_list[i])  == 0) {
                        net_device->nvsp_version = ver_list[i];
                        break;
                }

        if (i < 0) {
                ret = -EPROTO;
                goto cleanup;
        }

        pr_debug("Negotiated NVSP version:%x\n", net_device->nvsp_version);

        /* Send the ndis version */
        memset(init_packet, 0, sizeof(struct nvsp_message));

        if (net_device->nvsp_version <= NVSP_PROTOCOL_VERSION_4)
                ndis_version = 0x00060001;
        else
                ndis_version = 0x0006001e;

        init_packet->hdr.msg_type = NVSP_MSG1_TYPE_SEND_NDIS_VER;
        init_packet->msg.v1_msg.
                send_ndis_ver.ndis_major_ver =
                                (ndis_version & 0xFFFF0000) >> 16;
        init_packet->msg.v1_msg.
                send_ndis_ver.ndis_minor_ver =
                                ndis_version & 0xFFFF;

        /* Send the init request */
        ret = vmbus_sendpacket(device->channel, init_packet,
                                sizeof(struct nvsp_message),
                                (unsigned long)init_packet,
                                VM_PKT_DATA_INBAND, 0);
        if (ret != 0)
                goto cleanup;


        ret = netvsc_init_buf(device, net_device, device_info);

cleanup:
        return ret;
}

static void netvsc_disconnect_vsp(struct hv_device *device)
{
        netvsc_destroy_buf(device);
}

/*
 * netvsc_device_remove - Callback when the root bus device is removed
 */
void netvsc_device_remove(struct hv_device *device)
{
        struct net_device *ndev = hv_get_drvdata(device);
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        struct netvsc_device *net_device
                = rtnl_dereference(net_device_ctx->nvdev);
        int i;

        cancel_work_sync(&net_device->subchan_work);

        netvsc_disconnect_vsp(device);

        RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);

        /*
         * At this point, no one should be accessing net_device
         * except in here
         */
        netdev_dbg(ndev, "net device safe to remove\n");

        /* Now, we can close the channel safely */
        vmbus_close(device->channel);

        /* And dissassociate NAPI context from device */
        for (i = 0; i < net_device->num_chn; i++)
                netif_napi_del(&net_device->chan_table[i].napi);

        /* Release all resources */
        free_netvsc_device_rcu(net_device);
}

#define RING_AVAIL_PERCENT_HIWATER 20
#define RING_AVAIL_PERCENT_LOWATER 10

/*
 * Get the percentage of available bytes to write in the ring.
 * The return value is in range from 0 to 100.
 */
static inline u32 hv_ringbuf_avail_percent(
                struct hv_ring_buffer_info *ring_info)
{
        u32 avail_read, avail_write;

        hv_get_ringbuffer_availbytes(ring_info, &avail_read, &avail_write);

        return avail_write * 100 / ring_info->ring_datasize;
}

static inline void netvsc_free_send_slot(struct netvsc_device *net_device,
                                         u32 index)
{
        sync_change_bit(index, net_device->send_section_map);
}

static void netvsc_send_tx_complete(struct netvsc_device *net_device,
                                    struct vmbus_channel *incoming_channel,
                                    struct hv_device *device,
                                    const struct vmpacket_descriptor *desc,
                                    int budget)
{
        struct sk_buff *skb = (struct sk_buff *)(unsigned long)desc->trans_id;
        struct net_device *ndev = hv_get_drvdata(device);
        struct vmbus_channel *channel = device->channel;
        u16 q_idx = 0;
        int queue_sends;

        /* Notify the layer above us */
        if (likely(skb)) {
                const struct hv_netvsc_packet *packet
                        = (struct hv_netvsc_packet *)skb->cb;
                u32 send_index = packet->send_buf_index;
                struct netvsc_stats *tx_stats;

                if (send_index != NETVSC_INVALID_INDEX)
                        netvsc_free_send_slot(net_device, send_index);
                q_idx = packet->q_idx;
                channel = incoming_channel;

                tx_stats = &net_device->chan_table[q_idx].tx_stats;

                u64_stats_update_begin(&tx_stats->syncp);
                tx_stats->packets += packet->total_packets;
                tx_stats->bytes += packet->total_bytes;
                u64_stats_update_end(&tx_stats->syncp);

                napi_consume_skb(skb, budget);
        }

        queue_sends =
                atomic_dec_return(&net_device->chan_table[q_idx].queue_sends);

        if (net_device->destroy && queue_sends == 0)
                wake_up(&net_device->wait_drain);

        if (netif_tx_queue_stopped(netdev_get_tx_queue(ndev, q_idx)) &&
            (hv_ringbuf_avail_percent(&channel->outbound) > RING_AVAIL_PERCENT_HIWATER ||
             queue_sends < 1))
                netif_tx_wake_queue(netdev_get_tx_queue(ndev, q_idx));
}

static void netvsc_send_completion(struct netvsc_device *net_device,
                                   struct vmbus_channel *incoming_channel,
                                   struct hv_device *device,
                                   const struct vmpacket_descriptor *desc,
                                   int budget)
{
        struct nvsp_message *nvsp_packet = hv_pkt_data(desc);
        struct net_device *ndev = hv_get_drvdata(device);

        switch (nvsp_packet->hdr.msg_type) {
        case NVSP_MSG_TYPE_INIT_COMPLETE:
        case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
        case NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE:
        case NVSP_MSG5_TYPE_SUBCHANNEL:
                /* Copy the response back */
                memcpy(&net_device->channel_init_pkt, nvsp_packet,
                       sizeof(struct nvsp_message));
                complete(&net_device->channel_init_wait);
                break;

        case NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE:
                netvsc_send_tx_complete(net_device, incoming_channel,
                                        device, desc, budget);
                break;

        default:
                netdev_err(ndev,
                           "Unknown send completion type %d received!!\n",
                           nvsp_packet->hdr.msg_type);
        }
}

static u32 netvsc_get_next_send_section(struct netvsc_device *net_device)
{
        unsigned long *map_addr = net_device->send_section_map;
        unsigned int i;

        for_each_clear_bit(i, map_addr, net_device->send_section_cnt) {
                if (sync_test_and_set_bit(i, map_addr) == 0)
                        return i;
        }

        return NETVSC_INVALID_INDEX;
}

static u32 netvsc_copy_to_send_buf(struct netvsc_device *net_device,
                                   unsigned int section_index,
                                   u32 pend_size,
                                   struct hv_netvsc_packet *packet,
                                   struct rndis_message *rndis_msg,
                                   struct hv_page_buffer *pb,
                                   struct sk_buff *skb)
{
        char *start = net_device->send_buf;
        char *dest = start + (section_index * net_device->send_section_size)
                     + pend_size;
        int i;
        u32 msg_size = 0;
        u32 padding = 0;
        u32 remain = packet->total_data_buflen % net_device->pkt_align;
        u32 page_count = packet->cp_partial ? packet->rmsg_pgcnt :
                packet->page_buf_cnt;

        /* Add padding */
        if (skb->xmit_more && remain && !packet->cp_partial) {
                padding = net_device->pkt_align - remain;
                rndis_msg->msg_len += padding;
                packet->total_data_buflen += padding;
        }

        for (i = 0; i < page_count; i++) {
                char *src = phys_to_virt(pb[i].pfn << PAGE_SHIFT);
                u32 offset = pb[i].offset;
                u32 len = pb[i].len;

                memcpy(dest, (src + offset), len);
                msg_size += len;
                dest += len;
        }

        if (padding) {
                memset(dest, 0, padding);
                msg_size += padding;
        }

        return msg_size;
}

static inline int netvsc_send_pkt(
        struct hv_device *device,
        struct hv_netvsc_packet *packet,
        struct netvsc_device *net_device,
        struct hv_page_buffer *pb,
        struct sk_buff *skb)
{
        struct nvsp_message nvmsg;
        struct nvsp_1_message_send_rndis_packet * const rpkt =
                &nvmsg.msg.v1_msg.send_rndis_pkt;
        struct netvsc_channel * const nvchan =
                &net_device->chan_table[packet->q_idx];
        struct vmbus_channel *out_channel = nvchan->channel;
        struct net_device *ndev = hv_get_drvdata(device);
        struct netdev_queue *txq = netdev_get_tx_queue(ndev, packet->q_idx);
        u64 req_id;
        int ret;
        u32 ring_avail = hv_ringbuf_avail_percent(&out_channel->outbound);

        nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
        if (skb)
                rpkt->channel_type = 0;         /* 0 is RMC_DATA */
        else
                rpkt->channel_type = 1;         /* 1 is RMC_CONTROL */

        rpkt->send_buf_section_index = packet->send_buf_index;
        if (packet->send_buf_index == NETVSC_INVALID_INDEX)
                rpkt->send_buf_section_size = 0;
        else
                rpkt->send_buf_section_size = packet->total_data_buflen;

        req_id = (ulong)skb;

        if (out_channel->rescind)
                return -ENODEV;

        if (packet->page_buf_cnt) {
                if (packet->cp_partial)
                        pb += packet->rmsg_pgcnt;

                ret = vmbus_sendpacket_pagebuffer(out_channel,
                                                  pb, packet->page_buf_cnt,
                                                  &nvmsg, sizeof(nvmsg),
                                                  req_id);
        } else {
                ret = vmbus_sendpacket(out_channel,
                                       &nvmsg, sizeof(nvmsg),
                                       req_id, VM_PKT_DATA_INBAND,
                                       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        }

        if (ret == 0) {
                atomic_inc_return(&nvchan->queue_sends);

                if (ring_avail < RING_AVAIL_PERCENT_LOWATER)
                        netif_tx_stop_queue(txq);
        } else if (ret == -EAGAIN) {
                netif_tx_stop_queue(txq);
                if (atomic_read(&nvchan->queue_sends) < 1) {
                        netif_tx_wake_queue(txq);
                        ret = -ENOSPC;
                }
        } else {
                netdev_err(ndev,
                           "Unable to send packet pages %u len %u, ret %d\n",
                           packet->page_buf_cnt, packet->total_data_buflen,
                           ret);
        }

        return ret;
}

/* Move packet out of multi send data (msd), and clear msd */
static inline void move_pkt_msd(struct hv_netvsc_packet **msd_send,
                                struct sk_buff **msd_skb,
                                struct multi_send_data *msdp)
{
        *msd_skb = msdp->skb;
        *msd_send = msdp->pkt;
        msdp->skb = NULL;
        msdp->pkt = NULL;
        msdp->count = 0;
}

/* RCU already held by caller */
int netvsc_send(struct net_device_context *ndev_ctx,
                struct hv_netvsc_packet *packet,
                struct rndis_message *rndis_msg,
                struct hv_page_buffer *pb,
                struct sk_buff *skb)
{
        struct netvsc_device *net_device
                = rcu_dereference_bh(ndev_ctx->nvdev);
        struct hv_device *device = ndev_ctx->device_ctx;
        int ret = 0;
        struct netvsc_channel *nvchan;
        u32 pktlen = packet->total_data_buflen, msd_len = 0;
        unsigned int section_index = NETVSC_INVALID_INDEX;
        struct multi_send_data *msdp;
        struct hv_netvsc_packet *msd_send = NULL, *cur_send = NULL;
        struct sk_buff *msd_skb = NULL;
        bool try_batch;
        bool xmit_more = (skb != NULL) ? skb->xmit_more : false;

        /* If device is rescinded, return error and packet will get dropped. */
        if (unlikely(!net_device || net_device->destroy))
                return -ENODEV;

        /* We may race with netvsc_connect_vsp()/netvsc_init_buf() and get
         * here before the negotiation with the host is finished and
         * send_section_map may not be allocated yet.
         */
        if (unlikely(!net_device->send_section_map))
                return -EAGAIN;

        nvchan = &net_device->chan_table[packet->q_idx];
        packet->send_buf_index = NETVSC_INVALID_INDEX;
        packet->cp_partial = false;

        /* Send control message directly without accessing msd (Multi-Send
         * Data) field which may be changed during data packet processing.
         */
        if (!skb) {
                cur_send = packet;
                goto send_now;
        }

        /* batch packets in send buffer if possible */
        msdp = &nvchan->msd;
        if (msdp->pkt)
                msd_len = msdp->pkt->total_data_buflen;

        try_batch =  msd_len > 0 && msdp->count < net_device->max_pkt;
        if (try_batch && msd_len + pktlen + net_device->pkt_align <
            net_device->send_section_size) {
                section_index = msdp->pkt->send_buf_index;

        } else if (try_batch && msd_len + packet->rmsg_size <
                   net_device->send_section_size) {
                section_index = msdp->pkt->send_buf_index;
                packet->cp_partial = true;

        } else if (pktlen + net_device->pkt_align <
                   net_device->send_section_size) {
                section_index = netvsc_get_next_send_section(net_device);
                if (unlikely(section_index == NETVSC_INVALID_INDEX)) {
                        ++ndev_ctx->eth_stats.tx_send_full;
                } else {
                        move_pkt_msd(&msd_send, &msd_skb, msdp);
                        msd_len = 0;
                }
        }

        if (section_index != NETVSC_INVALID_INDEX) {
                netvsc_copy_to_send_buf(net_device,
                                        section_index, msd_len,
                                        packet, rndis_msg, pb, skb);

                packet->send_buf_index = section_index;

                if (packet->cp_partial) {
                        packet->page_buf_cnt -= packet->rmsg_pgcnt;
                        packet->total_data_buflen = msd_len + packet->rmsg_size;
                } else {
                        packet->page_buf_cnt = 0;
                        packet->total_data_buflen += msd_len;
                }

                if (msdp->pkt) {
                        packet->total_packets += msdp->pkt->total_packets;
                        packet->total_bytes += msdp->pkt->total_bytes;
                }

                if (msdp->skb)
                        dev_consume_skb_any(msdp->skb);

                if (xmit_more && !packet->cp_partial) {
                        msdp->skb = skb;
                        msdp->pkt = packet;
                        msdp->count++;
                } else {
                        cur_send = packet;
                        msdp->skb = NULL;
                        msdp->pkt = NULL;
                        msdp->count = 0;
                }
        } else {
                move_pkt_msd(&msd_send, &msd_skb, msdp);
                cur_send = packet;
        }

        if (msd_send) {
                int m_ret = netvsc_send_pkt(device, msd_send, net_device,
                                            NULL, msd_skb);

                if (m_ret != 0) {
                        netvsc_free_send_slot(net_device,
                                              msd_send->send_buf_index);
                        dev_kfree_skb_any(msd_skb);
                }
        }

send_now:
        if (cur_send)
                ret = netvsc_send_pkt(device, cur_send, net_device, pb, skb);

        if (ret != 0 && section_index != NETVSC_INVALID_INDEX)
                netvsc_free_send_slot(net_device, section_index);

        return ret;
}

/* Send pending recv completions */
static int send_recv_completions(struct net_device *ndev,
                                 struct netvsc_device *nvdev,
                                 struct netvsc_channel *nvchan)
{
        struct multi_recv_comp *mrc = &nvchan->mrc;
        struct recv_comp_msg {
                struct nvsp_message_header hdr;
                u32 status;
        }  __packed;
        struct recv_comp_msg msg = {
                .hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE,
        };
        int ret;

        while (mrc->first != mrc->next) {
                const struct recv_comp_data *rcd
                        = mrc->slots + mrc->first;

                msg.status = rcd->status;
                ret = vmbus_sendpacket(nvchan->channel, &msg, sizeof(msg),
                                       rcd->tid, VM_PKT_COMP, 0);
                if (unlikely(ret)) {
                        struct net_device_context *ndev_ctx = netdev_priv(ndev);

                        ++ndev_ctx->eth_stats.rx_comp_busy;
                        return ret;
                }

                if (++mrc->first == nvdev->recv_completion_cnt)
                        mrc->first = 0;
        }

        /* receive completion ring has been emptied */
        if (unlikely(nvdev->destroy))
                wake_up(&nvdev->wait_drain);

        return 0;
}

/* Count how many receive completions are outstanding */
static void recv_comp_slot_avail(const struct netvsc_device *nvdev,
                                 const struct multi_recv_comp *mrc,
                                 u32 *filled, u32 *avail)
{
        u32 count = nvdev->recv_completion_cnt;

        if (mrc->next >= mrc->first)
                *filled = mrc->next - mrc->first;
        else
                *filled = (count - mrc->first) + mrc->next;

        *avail = count - *filled - 1;
}

/* Add receive complete to ring to send to host. */
static void enq_receive_complete(struct net_device *ndev,
                                 struct netvsc_device *nvdev, u16 q_idx,
                                 u64 tid, u32 status)
{
        struct netvsc_channel *nvchan = &nvdev->chan_table[q_idx];
        struct multi_recv_comp *mrc = &nvchan->mrc;
        struct recv_comp_data *rcd;
        u32 filled, avail;

        recv_comp_slot_avail(nvdev, mrc, &filled, &avail);

        if (unlikely(filled > NAPI_POLL_WEIGHT)) {
                send_recv_completions(ndev, nvdev, nvchan);
                recv_comp_slot_avail(nvdev, mrc, &filled, &avail);
        }

        if (unlikely(!avail)) {
                netdev_err(ndev, "Recv_comp full buf q:%hd, tid:%llx\n",
                           q_idx, tid);
                return;
        }

        rcd = mrc->slots + mrc->next;
        rcd->tid = tid;
        rcd->status = status;

        if (++mrc->next == nvdev->recv_completion_cnt)
                mrc->next = 0;
}

static int netvsc_receive(struct net_device *ndev,
                          struct netvsc_device *net_device,
                          struct net_device_context *net_device_ctx,
                          struct hv_device *device,
                          struct vmbus_channel *channel,
                          const struct vmpacket_descriptor *desc,
                          struct nvsp_message *nvsp)
{
        const struct vmtransfer_page_packet_header *vmxferpage_packet
                = container_of(desc, const struct vmtransfer_page_packet_header, d);
        u16 q_idx = channel->offermsg.offer.sub_channel_index;
        char *recv_buf = net_device->recv_buf;
        u32 status = NVSP_STAT_SUCCESS;
        int i;
        int count = 0;

        /* Make sure this is a valid nvsp packet */
        if (unlikely(nvsp->hdr.msg_type != NVSP_MSG1_TYPE_SEND_RNDIS_PKT)) {
                netif_err(net_device_ctx, rx_err, ndev,
                          "Unknown nvsp packet type received %u\n",
                          nvsp->hdr.msg_type);
                return 0;
        }

        if (unlikely(vmxferpage_packet->xfer_pageset_id != NETVSC_RECEIVE_BUFFER_ID)) {
                netif_err(net_device_ctx, rx_err, ndev,
                          "Invalid xfer page set id - expecting %x got %x\n",
                          NETVSC_RECEIVE_BUFFER_ID,
                          vmxferpage_packet->xfer_pageset_id);
                return 0;
        }

        count = vmxferpage_packet->range_cnt;

        /* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
        for (i = 0; i < count; i++) {
                void *data = recv_buf
                        + vmxferpage_packet->ranges[i].byte_offset;
                u32 buflen = vmxferpage_packet->ranges[i].byte_count;

                /* Pass it to the upper layer */
                status = rndis_filter_receive(ndev, net_device, device,
                                              channel, data, buflen);
        }

        enq_receive_complete(ndev, net_device, q_idx,
                             vmxferpage_packet->d.trans_id, status);

        return count;
}

static void netvsc_send_table(struct hv_device *hdev,
                              struct nvsp_message *nvmsg)
{
        struct net_device *ndev = hv_get_drvdata(hdev);
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        int i;
        u32 count, *tab;

        count = nvmsg->msg.v5_msg.send_table.count;
        if (count != VRSS_SEND_TAB_SIZE) {
                netdev_err(ndev, "Received wrong send-table size:%u\n", count);
                return;
        }

        tab = (u32 *)((unsigned long)&nvmsg->msg.v5_msg.send_table +
                      nvmsg->msg.v5_msg.send_table.offset);

        for (i = 0; i < count; i++)
                net_device_ctx->tx_send_table[i] = tab[i];
}

static void netvsc_send_vf(struct net_device_context *net_device_ctx,
                           struct nvsp_message *nvmsg)
{
        net_device_ctx->vf_alloc = nvmsg->msg.v4_msg.vf_assoc.allocated;
        net_device_ctx->vf_serial = nvmsg->msg.v4_msg.vf_assoc.serial;
}

static inline void netvsc_receive_inband(struct hv_device *hdev,
                                 struct net_device_context *net_device_ctx,
                                 struct nvsp_message *nvmsg)
{
        switch (nvmsg->hdr.msg_type) {
        case NVSP_MSG5_TYPE_SEND_INDIRECTION_TABLE:
                netvsc_send_table(hdev, nvmsg);
                break;

        case NVSP_MSG4_TYPE_SEND_VF_ASSOCIATION:
                netvsc_send_vf(net_device_ctx, nvmsg);
                break;
        }
}

static int netvsc_process_raw_pkt(struct hv_device *device,
                                  struct vmbus_channel *channel,
                                  struct netvsc_device *net_device,
                                  struct net_device *ndev,
                                  const struct vmpacket_descriptor *desc,
                                  int budget)
{
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        struct nvsp_message *nvmsg = hv_pkt_data(desc);

        switch (desc->type) {
        case VM_PKT_COMP:
                netvsc_send_completion(net_device, channel, device,
                                       desc, budget);
                break;

        case VM_PKT_DATA_USING_XFER_PAGES:
                return netvsc_receive(ndev, net_device, net_device_ctx,
                                      device, channel, desc, nvmsg);
                break;

        case VM_PKT_DATA_INBAND:
                netvsc_receive_inband(device, net_device_ctx, nvmsg);
                break;

        default:
                netdev_err(ndev, "unhandled packet type %d, tid %llx\n",
                           desc->type, desc->trans_id);
                break;
        }

        return 0;
}

static struct hv_device *netvsc_channel_to_device(struct vmbus_channel *channel)
{
        struct vmbus_channel *primary = channel->primary_channel;

        return primary ? primary->device_obj : channel->device_obj;
}

/* Network processing softirq
 * Process data in incoming ring buffer from host
 * Stops when ring is empty or budget is met or exceeded.
 */
int netvsc_poll(struct napi_struct *napi, int budget)
{
        struct netvsc_channel *nvchan
                = container_of(napi, struct netvsc_channel, napi);
        struct netvsc_device *net_device = nvchan->net_device;
        struct vmbus_channel *channel = nvchan->channel;
        struct hv_device *device = netvsc_channel_to_device(channel);
        struct net_device *ndev = hv_get_drvdata(device);
        int work_done = 0;

        /* If starting a new interval */
        if (!nvchan->desc)
                nvchan->desc = hv_pkt_iter_first(channel);

        while (nvchan->desc && work_done < budget) {
                work_done += netvsc_process_raw_pkt(device, channel, net_device,
                                                    ndev, nvchan->desc, budget);
                nvchan->desc = hv_pkt_iter_next(channel, nvchan->desc);
        }

        /* If send of pending receive completions suceeded
         *   and did not exhaust NAPI budget this time
         *   and not doing busy poll
         * then re-enable host interrupts
         *     and reschedule if ring is not empty.
         */
        if (send_recv_completions(ndev, net_device, nvchan) == 0 &&
            work_done < budget &&
            napi_complete_done(napi, work_done) &&
            hv_end_read(&channel->inbound)) {
                hv_begin_read(&channel->inbound);
                napi_reschedule(napi);
        }

        /* Driver may overshoot since multiple packets per descriptor */
        return min(work_done, budget);
}

/* Call back when data is available in host ring buffer.
 * Processing is deferred until network softirq (NAPI)
 */
void netvsc_channel_cb(void *context)
{
        struct netvsc_channel *nvchan = context;
        struct vmbus_channel *channel = nvchan->channel;
        struct hv_ring_buffer_info *rbi = &channel->inbound;

        /* preload first vmpacket descriptor */
        prefetch(hv_get_ring_buffer(rbi) + rbi->priv_read_index);

        if (napi_schedule_prep(&nvchan->napi)) {
                /* disable interupts from host */
                hv_begin_read(rbi);

                __napi_schedule(&nvchan->napi);
        }
}

/*
 * netvsc_device_add - Callback when the device belonging to this
 * driver is added
 */
struct netvsc_device *netvsc_device_add(struct hv_device *device,
                                const struct netvsc_device_info *device_info)
{
        int i, ret = 0;
        int ring_size = device_info->ring_size;
        struct netvsc_device *net_device;
        struct net_device *ndev = hv_get_drvdata(device);
        struct net_device_context *net_device_ctx = netdev_priv(ndev);

        net_device = alloc_net_device();
        if (!net_device)
                return ERR_PTR(-ENOMEM);

        net_device->ring_size = ring_size;

        /* Because the device uses NAPI, all the interrupt batching and
         * control is done via Net softirq, not the channel handling
         */
        set_channel_read_mode(device->channel, HV_CALL_ISR);

        /* If we're reopening the device we may have multiple queues, fill the
         * chn_table with the default channel to use it before subchannels are
         * opened.
         * Initialize the channel state before we open;
         * we can be interrupted as soon as we open the channel.
         */

        for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
                struct netvsc_channel *nvchan = &net_device->chan_table[i];

                nvchan->channel = device->channel;
                nvchan->net_device = net_device;
                u64_stats_init(&nvchan->tx_stats.syncp);
                u64_stats_init(&nvchan->rx_stats.syncp);
        }

        /* Enable NAPI handler before init callbacks */
        netif_napi_add(ndev, &net_device->chan_table[0].napi,
                       netvsc_poll, NAPI_POLL_WEIGHT);

        /* Open the channel */
        ret = vmbus_open(device->channel, ring_size * PAGE_SIZE,
                         ring_size * PAGE_SIZE, NULL, 0,
                         netvsc_channel_cb,
                         net_device->chan_table);

        if (ret != 0) {
                netif_napi_del(&net_device->chan_table[0].napi);
                netdev_err(ndev, "unable to open channel: %d\n", ret);
                goto cleanup;
        }

        /* Channel is opened */
        netdev_dbg(ndev, "hv_netvsc channel opened successfully\n");

        napi_enable(&net_device->chan_table[0].napi);

        /* Writing nvdev pointer unlocks netvsc_send(), make sure chn_table is
         * populated.
         */
        rcu_assign_pointer(net_device_ctx->nvdev, net_device);

        /* Connect with the NetVsp */
        ret = netvsc_connect_vsp(device, net_device, device_info);
        if (ret != 0) {
                netdev_err(ndev,
                        "unable to connect to NetVSP - %d\n", ret);
                goto close;
        }

        return net_device;

close:
        RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
        napi_disable(&net_device->chan_table[0].napi);

        /* Now, we can close the channel safely */
        vmbus_close(device->channel);

cleanup:
        free_netvsc_device(&net_device->rcu);

        return ERR_PTR(ret);
}