/*
 * 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 <asm/sync_bitops.h>

#include "hyperv_net.h"


static struct netvsc_device *alloc_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;
        struct net_device *ndev = hv_get_drvdata(device);
        int i;

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

        net_device->cb_buffer = kzalloc(NETVSC_PACKET_SIZE, GFP_KERNEL);
        if (!net_device->cb_buffer) {
                kfree(net_device);
                return NULL;
        }

        init_waitqueue_head(&net_device->wait_drain);
        net_device->start_remove = false;
        net_device->destroy = false;
        net_device->dev = device;
        net_device->ndev = ndev;
        net_device->max_pkt = RNDIS_MAX_PKT_DEFAULT;
        net_device->pkt_align = RNDIS_PKT_ALIGN_DEFAULT;

        for (i = 0; i < num_online_cpus(); i++)
                spin_lock_init(&net_device->msd[i].lock);

        hv_set_drvdata(device, net_device);
        return net_device;
}

static void free_netvsc_device(struct netvsc_device *nvdev)
{
        kfree(nvdev->cb_buffer);
        kfree(nvdev);
}

static struct netvsc_device *get_outbound_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = hv_get_drvdata(device);
        if (net_device && net_device->destroy)
                net_device = NULL;

        return net_device;
}

static struct netvsc_device *get_inbound_net_device(struct hv_device *device)
{
        struct netvsc_device *net_device;

        net_device = hv_get_drvdata(device);

        if (!net_device)
                goto get_in_err;

        if (net_device->destroy &&
                atomic_read(&net_device->num_outstanding_sends) == 0)
                net_device = NULL;

get_in_err:
        return net_device;
}


static int netvsc_destroy_buf(struct netvsc_device *net_device)
{
        struct nvsp_message *revoke_packet;
        int ret = 0;
        struct net_device *ndev = net_device->ndev;

        /*
         * 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(net_device->dev->channel,
                                       revoke_packet,
                                       sizeof(struct nvsp_message),
                                       (unsigned long)revoke_packet,
                                       VM_PKT_DATA_INBAND, 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 ret;
                }
        }

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

        if (net_device->recv_section) {
                net_device->recv_section_cnt = 0;
                kfree(net_device->recv_section);
                net_device->recv_section = 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_size) {
                /* 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(net_device->dev->channel,
                                       revoke_packet,
                                       sizeof(struct nvsp_message),
                                       (unsigned long)revoke_packet,
                                       VM_PKT_DATA_INBAND, 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 ret;
                }
        }
        /* Teardown the gpadl on the vsp end */
        if (net_device->send_buf_gpadl_handle) {
                ret = vmbus_teardown_gpadl(net_device->dev->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 ret;
                }
                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);

        return ret;
}

static int netvsc_init_buf(struct hv_device *device)
{
        int ret = 0;
        unsigned long t;
        struct netvsc_device *net_device;
        struct nvsp_message *init_packet;
        struct net_device *ndev;
        int node;

        net_device = get_outbound_net_device(device);
        if (!net_device)
                return -ENODEV;
        ndev = net_device->ndev;

        node = cpu_to_node(device->channel->target_cpu);
        net_device->recv_buf = vzalloc_node(net_device->recv_buf_size, node);
        if (!net_device->recv_buf)
                net_device->recv_buf = vzalloc(net_device->recv_buf_size);

        if (!net_device->recv_buf) {
                netdev_err(ndev, "unable to allocate receive "
                        "buffer of size %d\n", net_device->recv_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,
                                    net_device->recv_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;
        }

        t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
        BUG_ON(t == 0);


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

        /* Parse the response */

        net_device->recv_section_cnt = init_packet->msg.
                v1_msg.send_recv_buf_complete.num_sections;

        net_device->recv_section = kmemdup(
                init_packet->msg.v1_msg.send_recv_buf_complete.sections,
                net_device->recv_section_cnt *
                sizeof(struct nvsp_1_receive_buffer_section),
                GFP_KERNEL);
        if (net_device->recv_section == NULL) {
                ret = -EINVAL;
                goto cleanup;
        }

        /*
         * For 1st release, there should only be 1 section that represents the
         * entire receive buffer
         */
        if (net_device->recv_section_cnt != 1 ||
            net_device->recv_section->offset != 0) {
                ret = -EINVAL;
                goto cleanup;
        }

        /* Now setup the send buffer.
         */
        net_device->send_buf = vzalloc_node(net_device->send_buf_size, node);
        if (!net_device->send_buf)
                net_device->send_buf = vzalloc(net_device->send_buf_size);
        if (!net_device->send_buf) {
                netdev_err(ndev, "unable to allocate send "
                           "buffer of size %d\n", net_device->send_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,
                                    net_device->send_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;
        }

        t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);
        BUG_ON(t == 0);

        /* 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 =
                net_device->send_buf_size/net_device->send_section_size;

        dev_info(&device->device, "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. */
        net_device->map_words = DIV_ROUND_UP(net_device->send_section_cnt,
                                             BITS_PER_LONG);

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

        goto exit;

cleanup:
        netvsc_destroy_buf(net_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)
{
        int ret;
        unsigned long t;

        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;

        t = wait_for_completion_timeout(&net_device->channel_init_wait, 5*HZ);

        if (t == 0)
                return -ETIMEDOUT;

        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 = net_device->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;

        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)
{
        int ret;
        struct netvsc_device *net_device;
        struct nvsp_message *init_packet;
        int ndis_version;
        struct net_device *ndev;
        u32 ver_list[] = { NVSP_PROTOCOL_VERSION_1, NVSP_PROTOCOL_VERSION_2,
                NVSP_PROTOCOL_VERSION_4, NVSP_PROTOCOL_VERSION_5 };
        int i, num_ver = 4; /* number of different NVSP versions */

        net_device = get_outbound_net_device(device);
        if (!net_device)
                return -ENODEV;
        ndev = net_device->ndev;

        init_packet = &net_device->channel_init_pkt;

        /* Negotiate the latest NVSP protocol supported */
        for (i = num_ver - 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;

        /* Post the big receive buffer to NetVSP */
        if (net_device->nvsp_version <= NVSP_PROTOCOL_VERSION_2)
                net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE_LEGACY;
        else
                net_device->recv_buf_size = NETVSC_RECEIVE_BUFFER_SIZE;
        net_device->send_buf_size = NETVSC_SEND_BUFFER_SIZE;

        ret = netvsc_init_buf(device);

cleanup:
        return ret;
}

static void netvsc_disconnect_vsp(struct netvsc_device *net_device)
{
        netvsc_destroy_buf(net_device);
}

/*
 * netvsc_device_remove - Callback when the root bus device is removed
 */
int netvsc_device_remove(struct hv_device *device)
{
        struct netvsc_device *net_device;
        unsigned long flags;

        net_device = hv_get_drvdata(device);

        netvsc_disconnect_vsp(net_device);

        /*
         * Since we have already drained, we don't need to busy wait
         * as was done in final_release_stor_device()
         * Note that we cannot set the ext pointer to NULL until
         * we have drained - to drain the outgoing packets, we need to
         * allow incoming packets.
         */

        spin_lock_irqsave(&device->channel->inbound_lock, flags);
        hv_set_drvdata(device, NULL);
        spin_unlock_irqrestore(&device->channel->inbound_lock, flags);

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

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

        /* Release all resources */
        vfree(net_device->sub_cb_buf);
        free_netvsc_device(net_device);
        return 0;
}


#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_completion(struct netvsc_device *net_device,
                                   struct hv_device *device,
                                   struct vmpacket_descriptor *packet)
{
        struct nvsp_message *nvsp_packet;
        struct hv_netvsc_packet *nvsc_packet;
        struct net_device *ndev;
        u32 send_index;

        ndev = net_device->ndev;

        nvsp_packet = (struct nvsp_message *)((unsigned long)packet +
                        (packet->offset8 << 3));

        if ((nvsp_packet->hdr.msg_type == NVSP_MSG_TYPE_INIT_COMPLETE) ||
            (nvsp_packet->hdr.msg_type ==
             NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE) ||
            (nvsp_packet->hdr.msg_type ==
             NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE) ||
            (nvsp_packet->hdr.msg_type ==
             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);
        } else if (nvsp_packet->hdr.msg_type ==
                   NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE) {
                int num_outstanding_sends;
                u16 q_idx = 0;
                struct vmbus_channel *channel = device->channel;
                int queue_sends;

                /* Get the send context */
                nvsc_packet = (struct hv_netvsc_packet *)(unsigned long)
                        packet->trans_id;

                /* Notify the layer above us */
                if (nvsc_packet) {
                        send_index = nvsc_packet->send_buf_index;
                        if (send_index != NETVSC_INVALID_INDEX)
                                netvsc_free_send_slot(net_device, send_index);
                        q_idx = nvsc_packet->q_idx;
                        channel = nvsc_packet->channel;
                        nvsc_packet->send_completion(nvsc_packet->
                                                     send_completion_ctx);
                }

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

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

                if (netif_tx_queue_stopped(netdev_get_tx_queue(ndev, q_idx)) &&
                    !net_device->start_remove &&
                    (hv_ringbuf_avail_percent(&channel->outbound) >
                     RING_AVAIL_PERCENT_HIWATER || queue_sends < 1))
                                netif_tx_wake_queue(netdev_get_tx_queue(
                                                    ndev, q_idx));
        } else {
                netdev_err(ndev, "Unknown send completion packet type- "
                           "%d received!!\n", nvsp_packet->hdr.msg_type);
        }

}

static u32 netvsc_get_next_send_section(struct netvsc_device *net_device)
{
        unsigned long index;
        u32 max_words = net_device->map_words;
        unsigned long *map_addr = (unsigned long *)net_device->send_section_map;
        u32 section_cnt = net_device->send_section_cnt;
        int ret_val = NETVSC_INVALID_INDEX;
        int i;
        int prev_val;

        for (i = 0; i < max_words; i++) {
                if (!~(map_addr[i]))
                        continue;
                index = ffz(map_addr[i]);
                prev_val = sync_test_and_set_bit(index, &map_addr[i]);
                if (prev_val)
                        continue;
                if ((index + (i * BITS_PER_LONG)) >= section_cnt)
                        break;
                ret_val = (index + (i * BITS_PER_LONG));
                break;
        }
        return ret_val;
}

static u32 netvsc_copy_to_send_buf(struct netvsc_device *net_device,
                                   unsigned int section_index,
                                   u32 pend_size,
                                   struct hv_netvsc_packet *packet)
{
        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 (packet->is_data_pkt && packet->xmit_more && remain &&
            !packet->cp_partial) {
                padding = net_device->pkt_align - remain;
                packet->rndis_msg->msg_len += padding;
                packet->total_data_buflen += padding;
        }

        for (i = 0; i < page_count; i++) {
                char *src = phys_to_virt(packet->page_buf[i].pfn << PAGE_SHIFT);
                u32 offset = packet->page_buf[i].offset;
                u32 len = packet->page_buf[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_netvsc_packet *packet,
        struct netvsc_device *net_device)
{
        struct nvsp_message nvmsg;
        struct vmbus_channel *out_channel = packet->channel;
        u16 q_idx = packet->q_idx;
        struct net_device *ndev = net_device->ndev;
        u64 req_id;
        int ret;
        struct hv_page_buffer *pgbuf;
        u32 ring_avail = hv_ringbuf_avail_percent(&out_channel->outbound);

        nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
        if (packet->is_data_pkt) {
                /* 0 is RMC_DATA; */
                nvmsg.msg.v1_msg.send_rndis_pkt.channel_type = 0;
        } else {
                /* 1 is RMC_CONTROL; */
                nvmsg.msg.v1_msg.send_rndis_pkt.channel_type = 1;
        }

        nvmsg.msg.v1_msg.send_rndis_pkt.send_buf_section_index =
                packet->send_buf_index;
        if (packet->send_buf_index == NETVSC_INVALID_INDEX)
                nvmsg.msg.v1_msg.send_rndis_pkt.send_buf_section_size = 0;
        else
                nvmsg.msg.v1_msg.send_rndis_pkt.send_buf_section_size =
                        packet->total_data_buflen;

        if (packet->send_completion)
                req_id = (ulong)packet;
        else
                req_id = 0;

        if (out_channel->rescind)
                return -ENODEV;

        /*
         * It is possible that once we successfully place this packet
         * on the ringbuffer, we may stop the queue. In that case, we want
         * to notify the host independent of the xmit_more flag. We don't
         * need to be precise here; in the worst case we may signal the host
         * unnecessarily.
         */
        if (ring_avail < (RING_AVAIL_PERCENT_LOWATER + 1))
                packet->xmit_more = false;

        if (packet->page_buf_cnt) {
                pgbuf = packet->cp_partial ? packet->page_buf +
                        packet->rmsg_pgcnt : packet->page_buf;
                ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
                                                      pgbuf,
                                                      packet->page_buf_cnt,
                                                      &nvmsg,
                                                      sizeof(struct nvsp_message),
                                                      req_id,
                                                      VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED,
                                                      !packet->xmit_more);
        } else {
                ret = vmbus_sendpacket_ctl(out_channel, &nvmsg,
                                           sizeof(struct nvsp_message),
                                           req_id,
                                           VM_PKT_DATA_INBAND,
                                           VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED,
                                           !packet->xmit_more);
        }

        if (ret == 0) {
                atomic_inc(&net_device->num_outstanding_sends);
                atomic_inc(&net_device->queue_sends[q_idx]);

                if (ring_avail < RING_AVAIL_PERCENT_LOWATER) {
                        netif_tx_stop_queue(netdev_get_tx_queue(ndev, q_idx));

                        if (atomic_read(&net_device->
                                queue_sends[q_idx]) < 1)
                                netif_tx_wake_queue(netdev_get_tx_queue(
                                                    ndev, q_idx));
                }
        } else if (ret == -EAGAIN) {
                netif_tx_stop_queue(netdev_get_tx_queue(
                                    ndev, q_idx));
                if (atomic_read(&net_device->queue_sends[q_idx]) < 1) {
                        netif_tx_wake_queue(netdev_get_tx_queue(
                                            ndev, q_idx));
                        ret = -ENOSPC;
                }
        } else {
                netdev_err(ndev, "Unable to send packet %p ret %d\n",
                           packet, ret);
        }

        return ret;
}

int netvsc_send(struct hv_device *device,
                struct hv_netvsc_packet *packet)
{
        struct netvsc_device *net_device;
        int ret = 0, m_ret = 0;
        struct vmbus_channel *out_channel;
        u16 q_idx = packet->q_idx;
        u32 pktlen = packet->total_data_buflen, msd_len = 0;
        unsigned int section_index = NETVSC_INVALID_INDEX;
        unsigned long flag;
        struct multi_send_data *msdp;
        struct hv_netvsc_packet *msd_send = NULL, *cur_send = NULL;
        bool try_batch;

        net_device = get_outbound_net_device(device);
        if (!net_device)
                return -ENODEV;

        out_channel = net_device->chn_table[q_idx];
        if (!out_channel) {
                out_channel = device->channel;
                q_idx = 0;
                packet->q_idx = 0;
        }
        packet->channel = out_channel;
        packet->send_buf_index = NETVSC_INVALID_INDEX;
        packet->cp_partial = false;

        msdp = &net_device->msd[q_idx];

        /* batch packets in send buffer if possible */
        spin_lock_irqsave(&msdp->lock, flag);
        if (msdp->pkt)
                msd_len = msdp->pkt->total_data_buflen;

        try_batch = packet->is_data_pkt && 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 (packet->is_data_pkt && pktlen + net_device->pkt_align <
                   net_device->send_section_size) {
                section_index = netvsc_get_next_send_section(net_device);
                if (section_index != NETVSC_INVALID_INDEX) {
                                msd_send = msdp->pkt;
                                msdp->pkt = NULL;
                                msdp->count = 0;
                                msd_len = 0;
                }
        }

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

                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)
                        netvsc_xmit_completion(msdp->pkt);

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

        spin_unlock_irqrestore(&msdp->lock, flag);

        if (msd_send) {
                m_ret = netvsc_send_pkt(msd_send, net_device);

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

        if (cur_send)
                ret = netvsc_send_pkt(cur_send, net_device);

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

        return ret;
}

static void netvsc_send_recv_completion(struct hv_device *device,
                                        struct vmbus_channel *channel,
                                        struct netvsc_device *net_device,
                                        u64 transaction_id, u32 status)
{
        struct nvsp_message recvcompMessage;
        int retries = 0;
        int ret;
        struct net_device *ndev;

        ndev = net_device->ndev;

        recvcompMessage.hdr.msg_type =
                                NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE;

        recvcompMessage.msg.v1_msg.send_rndis_pkt_complete.status = status;

retry_send_cmplt:
        /* Send the completion */
        ret = vmbus_sendpacket(channel, &recvcompMessage,
                               sizeof(struct nvsp_message), transaction_id,
                               VM_PKT_COMP, 0);
        if (ret == 0) {
                /* success */
                /* no-op */
        } else if (ret == -EAGAIN) {
                /* no more room...wait a bit and attempt to retry 3 times */
                retries++;
                netdev_err(ndev, "unable to send receive completion pkt"
                        " (tid %llx)...retrying %d\n", transaction_id, retries);

                if (retries < 4) {
                        udelay(100);
                        goto retry_send_cmplt;
                } else {
                        netdev_err(ndev, "unable to send receive "
                                "completion pkt (tid %llx)...give up retrying\n",
                                transaction_id);
                }
        } else {
                netdev_err(ndev, "unable to send receive "
                        "completion pkt - %llx\n", transaction_id);
        }
}

static void netvsc_receive(struct netvsc_device *net_device,
                        struct vmbus_channel *channel,

                        struct hv_device *device,
                        struct vmpacket_descriptor *packet)
{
        struct vmtransfer_page_packet_header *vmxferpage_packet;
        struct nvsp_message *nvsp_packet;
        struct hv_netvsc_packet nv_pkt;
        struct hv_netvsc_packet *netvsc_packet = &nv_pkt;
        u32 status = NVSP_STAT_SUCCESS;
        int i;
        int count = 0;
        struct net_device *ndev;

        ndev = net_device->ndev;

        /*
         * All inbound packets other than send completion should be xfer page
         * packet
         */
        if (packet->type != VM_PKT_DATA_USING_XFER_PAGES) {
                netdev_err(ndev, "Unknown packet type received - %d\n",
                           packet->type);
                return;
        }

        nvsp_packet = (struct nvsp_message *)((unsigned long)packet +
                        (packet->offset8 << 3));

        /* Make sure this is a valid nvsp packet */
        if (nvsp_packet->hdr.msg_type !=
            NVSP_MSG1_TYPE_SEND_RNDIS_PKT) {
                netdev_err(ndev, "Unknown nvsp packet type received-"
                        " %d\n", nvsp_packet->hdr.msg_type);
                return;
        }

        vmxferpage_packet = (struct vmtransfer_page_packet_header *)packet;

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

        count = vmxferpage_packet->range_cnt;
        netvsc_packet->channel = channel;

        /* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
        for (i = 0; i < count; i++) {
                /* Initialize the netvsc packet */
                netvsc_packet->status = NVSP_STAT_SUCCESS;
                netvsc_packet->data = (void *)((unsigned long)net_device->
                        recv_buf + vmxferpage_packet->ranges[i].byte_offset);
                netvsc_packet->total_data_buflen =
                                        vmxferpage_packet->ranges[i].byte_count;

                /* Pass it to the upper layer */
                rndis_filter_receive(device, netvsc_packet);

                if (netvsc_packet->status != NVSP_STAT_SUCCESS)
                        status = NVSP_STAT_FAIL;
        }

        netvsc_send_recv_completion(device, channel, net_device,
                                    vmxferpage_packet->d.trans_id, status);
}


static void netvsc_send_table(struct hv_device *hdev,
                              struct nvsp_message *nvmsg)
{
        struct netvsc_device *nvscdev;
        struct net_device *ndev;
        int i;
        u32 count, *tab;

        nvscdev = get_outbound_net_device(hdev);
        if (!nvscdev)
                return;
        ndev = nvscdev->ndev;

        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++)
                nvscdev->send_table[i] = tab[i];
}

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

static inline void netvsc_receive_inband(struct hv_device *hdev,
                                         struct netvsc_device *nvdev,
                                         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(nvdev, nvmsg);
                break;
        }
}

void netvsc_channel_cb(void *context)
{
        int ret;
        struct vmbus_channel *channel = (struct vmbus_channel *)context;
        struct hv_device *device;
        struct netvsc_device *net_device;
        u32 bytes_recvd;
        u64 request_id;
        struct vmpacket_descriptor *desc;
        unsigned char *buffer;
        int bufferlen = NETVSC_PACKET_SIZE;
        struct net_device *ndev;
        struct nvsp_message *nvmsg;

        if (channel->primary_channel != NULL)
                device = channel->primary_channel->device_obj;
        else
                device = channel->device_obj;

        net_device = get_inbound_net_device(device);
        if (!net_device)
                return;
        ndev = net_device->ndev;
        buffer = get_per_channel_state(channel);

        do {
                ret = vmbus_recvpacket_raw(channel, buffer, bufferlen,
                                           &bytes_recvd, &request_id);
                if (ret == 0) {
                        if (bytes_recvd > 0) {
                                desc = (struct vmpacket_descriptor *)buffer;
                                nvmsg = (struct nvsp_message *)((unsigned long)
                                         desc + (desc->offset8 << 3));
                                switch (desc->type) {
                                case VM_PKT_COMP:
                                        netvsc_send_completion(net_device,
                                                                device, desc);
                                        break;

                                case VM_PKT_DATA_USING_XFER_PAGES:
                                        netvsc_receive(net_device, channel,
                                                       device, desc);
                                        break;

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

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

                        } else {
                                /*
                                 * We are done for this pass.
                                 */
                                break;
                        }

                } else if (ret == -ENOBUFS) {
                        if (bufferlen > NETVSC_PACKET_SIZE)
                                kfree(buffer);
                        /* Handle large packet */
                        buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
                        if (buffer == NULL) {
                                /* Try again next time around */
                                netdev_err(ndev,
                                           "unable to allocate buffer of size "
                                           "(%d)!!\n", bytes_recvd);
                                break;
                        }

                        bufferlen = bytes_recvd;
                }
        } while (1);

        if (bufferlen > NETVSC_PACKET_SIZE)
                kfree(buffer);
        return;
}

/*
 * netvsc_device_add - Callback when the device belonging to this
 * driver is added
 */
int netvsc_device_add(struct hv_device *device, void *additional_info)
{
        int ret = 0;
        int ring_size =
        ((struct netvsc_device_info *)additional_info)->ring_size;
        struct netvsc_device *net_device;
        struct net_device *ndev;

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

        net_device->ring_size = ring_size;

        /*
         * Coming into this function, struct net_device * is
         * registered as the driver private data.
         * In alloc_net_device(), we register struct netvsc_device *
         * as the driver private data and stash away struct net_device *
         * in struct netvsc_device *.
         */
        ndev = net_device->ndev;

        /* Add netvsc_device context to netvsc_device */
        net_device->nd_ctx = netdev_priv(ndev);

        /* Initialize the NetVSC channel extension */
        init_completion(&net_device->channel_init_wait);

        set_per_channel_state(device->channel, net_device->cb_buffer);

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

        if (ret != 0) {
                netdev_err(ndev, "unable to open channel: %d\n", ret);
                goto cleanup;
        }

        /* Channel is opened */
        pr_info("hv_netvsc channel opened successfully\n");

        net_device->chn_table[0] = device->channel;

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

        return ret;

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

cleanup:
        free_netvsc_device(net_device);

        return ret;
}