Merge tag 'char-misc-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregk...

[mirror_ubuntu-artful-kernel.git] / drivers / net / hyperv / netvsc.c

/*
 * 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"

/*
 * 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 = 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;

        net_device->chan_table[0].mrc.buf
                = vzalloc(NETVSC_RECVSLOT_MAX * sizeof(struct recv_comp_data));

        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);

        return net_device;
}

static void free_netvsc_device(struct netvsc_device *nvdev)
{
        int i;

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

        kfree(nvdev);
}


static inline bool netvsc_channel_idle(const struct netvsc_device *net_device,
                                       u16 q_idx)
{
        const struct netvsc_channel *nvchan = &net_device->chan_table[q_idx];

        return atomic_read(&net_device->num_outstanding_recvs) == 0 &&
                atomic_read(&nvchan->queue_sends) == 0;
}

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

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

        return net_device;
}

static void netvsc_destroy_buf(struct hv_device *device)
{
        struct nvsp_message *revoke_packet;
        struct net_device *ndev = hv_get_drvdata(device);
        struct netvsc_device *net_device = net_device_to_netvsc_device(ndev);
        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 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;
                }
        }

        /* 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;
        }

        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(device->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;
                }
        }
        /* 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);
}

static int netvsc_init_buf(struct hv_device *device)
{
        int ret = 0;
        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 = hv_get_drvdata(device);

        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;
        }

        wait_for_completion(&net_device->channel_init_wait);

        /* 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;
        }

        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 =
                net_device->send_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. */
        net_device->map_words = DIV_ROUND_UP(net_device->send_section_cnt,
                                             BITS_PER_LONG);

        net_device->send_section_map = kcalloc(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(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)
{
        int ret;
        struct netvsc_device *net_device;
        struct nvsp_message *init_packet;
        int ndis_version;
        const u32 ver_list[] = {
                NVSP_PROTOCOL_VERSION_1, NVSP_PROTOCOL_VERSION_2,
                NVSP_PROTOCOL_VERSION_4, NVSP_PROTOCOL_VERSION_5 };
        int i;

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

        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;

        /* 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 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 = net_device_ctx->nvdev;

        netvsc_disconnect_vsp(device);

        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);

        /* Release all resources */
        free_netvsc_device(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,
                                    struct vmpacket_descriptor *packet)
{
        struct sk_buff *skb = (struct sk_buff *)(unsigned long)packet->trans_id;
        struct net_device *ndev = hv_get_drvdata(device);
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        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);

                dev_consume_skb_any(skb);
        }

        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)) &&
            !net_device_ctx->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));
}

static void netvsc_send_completion(struct netvsc_device *net_device,
                                   struct vmbus_channel *incoming_channel,
                                   struct hv_device *device,
                                   struct vmpacket_descriptor *packet)
{
        struct nvsp_message *nvsp_packet;
        struct net_device *ndev = hv_get_drvdata(device);

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

        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, packet);
                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->map_words) {
                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 && 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 netvsc_channel *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;
        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 (skb != NULL) {
                /* 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;

        req_id = (ulong)skb;

        if (out_channel->rescind)
                return -ENODEV;

        if (packet->page_buf_cnt) {
                pgbuf = packet->cp_partial ? (*pb) +
                        packet->rmsg_pgcnt : (*pb);
                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);
        } else {
                ret = vmbus_sendpacket_ctl(out_channel, &nvmsg,
                                           sizeof(struct nvsp_message),
                                           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 %p ret %d\n",
                           packet, 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;
}

int netvsc_send(struct hv_device *device,
                struct hv_netvsc_packet *packet,
                struct rndis_message *rndis_msg,
                struct hv_page_buffer **pb,
                struct sk_buff *skb)
{
        struct netvsc_device *net_device;
        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;

        net_device = get_outbound_net_device(device);
        if (!net_device)
                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 (!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 = (skb != NULL) && 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 ((skb != NULL) && 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) {
                        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;
}

static int netvsc_send_recv_completion(struct vmbus_channel *channel,
                                       u64 transaction_id, u32 status)
{
        struct nvsp_message recvcompMessage;
        int ret;

        recvcompMessage.hdr.msg_type =
                                NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE;

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

        /* Send the completion */
        ret = vmbus_sendpacket(channel, &recvcompMessage,
                               sizeof(struct nvsp_message_header) + sizeof(u32),
                               transaction_id, VM_PKT_COMP, 0);

        return ret;
}

static inline void count_recv_comp_slot(struct netvsc_device *nvdev, u16 q_idx,
                                        u32 *filled, u32 *avail)
{
        struct multi_recv_comp *mrc = &nvdev->chan_table[q_idx].mrc;
        u32 first = mrc->first;
        u32 next = mrc->next;

        *filled = (first > next) ? NETVSC_RECVSLOT_MAX - first + next :
                  next - first;

        *avail = NETVSC_RECVSLOT_MAX - *filled - 1;
}

/* Read the first filled slot, no change to index */
static inline struct recv_comp_data *read_recv_comp_slot(struct netvsc_device
                                                         *nvdev, u16 q_idx)
{
        struct multi_recv_comp *mrc = &nvdev->chan_table[q_idx].mrc;
        u32 filled, avail;

        if (unlikely(!mrc->buf))
                return NULL;

        count_recv_comp_slot(nvdev, q_idx, &filled, &avail);
        if (!filled)
                return NULL;

        return mrc->buf + mrc->first * sizeof(struct recv_comp_data);
}

/* Put the first filled slot back to available pool */
static inline void put_recv_comp_slot(struct netvsc_device *nvdev, u16 q_idx)
{
        struct multi_recv_comp *mrc = &nvdev->chan_table[q_idx].mrc;
        int num_recv;

        mrc->first = (mrc->first + 1) % NETVSC_RECVSLOT_MAX;

        num_recv = atomic_dec_return(&nvdev->num_outstanding_recvs);

        if (nvdev->destroy && num_recv == 0)
                wake_up(&nvdev->wait_drain);
}

/* Check and send pending recv completions */
static void netvsc_chk_recv_comp(struct netvsc_device *nvdev,
                                 struct vmbus_channel *channel, u16 q_idx)
{
        struct recv_comp_data *rcd;
        int ret;

        while (true) {
                rcd = read_recv_comp_slot(nvdev, q_idx);
                if (!rcd)
                        break;

                ret = netvsc_send_recv_completion(channel, rcd->tid,
                                                  rcd->status);
                if (ret)
                        break;

                put_recv_comp_slot(nvdev, q_idx);
        }
}

#define NETVSC_RCD_WATERMARK 80

/* Get next available slot */
static inline struct recv_comp_data *get_recv_comp_slot(
        struct netvsc_device *nvdev, struct vmbus_channel *channel, u16 q_idx)
{
        struct multi_recv_comp *mrc = &nvdev->chan_table[q_idx].mrc;
        u32 filled, avail, next;
        struct recv_comp_data *rcd;

        if (unlikely(!nvdev->recv_section))
                return NULL;

        if (unlikely(!mrc->buf))
                return NULL;

        if (atomic_read(&nvdev->num_outstanding_recvs) >
            nvdev->recv_section->num_sub_allocs * NETVSC_RCD_WATERMARK / 100)
                netvsc_chk_recv_comp(nvdev, channel, q_idx);

        count_recv_comp_slot(nvdev, q_idx, &filled, &avail);
        if (!avail)
                return NULL;

        next = mrc->next;
        rcd = mrc->buf + next * sizeof(struct recv_comp_data);
        mrc->next = (next + 1) % NETVSC_RECVSLOT_MAX;

        atomic_inc(&nvdev->num_outstanding_recvs);

        return rcd;
}

static void 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,
                   struct vmtransfer_page_packet_header *vmxferpage_packet,
                   struct nvsp_message *nvsp)
{
        char *recv_buf = net_device->recv_buf;
        u32 status = NVSP_STAT_SUCCESS;
        int i;
        int count = 0;
        int ret;
        struct recv_comp_data *rcd;
        u16 q_idx = channel->offermsg.offer.sub_channel_index;

        /* 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;
        }

        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;
        }

        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);
        }

        if (!net_device->chan_table[q_idx].mrc.buf) {
                ret = netvsc_send_recv_completion(channel,
                                                  vmxferpage_packet->d.trans_id,
                                                  status);
                if (ret)
                        netdev_err(ndev, "Recv_comp q:%hd, tid:%llx, err:%d\n",
                                   q_idx, vmxferpage_packet->d.trans_id, ret);
                return;
        }

        rcd = get_recv_comp_slot(net_device, channel, q_idx);

        if (!rcd) {
                netdev_err(ndev, "Recv_comp full buf q:%hd, tid:%llx\n",
                           q_idx, vmxferpage_packet->d.trans_id);
                return;
        }

        rcd->tid = vmxferpage_packet->d.trans_id;
        rcd->status = status;
}

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

        nvscdev = get_outbound_net_device(hdev);
        if (!nvscdev)
                return;

        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 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 void netvsc_process_raw_pkt(struct hv_device *device,
                                   struct vmbus_channel *channel,
                                   struct netvsc_device *net_device,
                                   struct net_device *ndev,
                                   u64 request_id,
                                   struct vmpacket_descriptor *desc)
{
        struct net_device_context *net_device_ctx = netdev_priv(ndev);
        struct nvsp_message *nvmsg
                = (struct nvsp_message *)((unsigned long)desc
                                          + (desc->offset8 << 3));

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

        case VM_PKT_DATA_USING_XFER_PAGES:
                netvsc_receive(ndev, net_device, net_device_ctx,
                               device, channel,
                               (struct vmtransfer_page_packet_header *)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, request_id);
                break;
        }
}

void netvsc_channel_cb(void *context)
{
        struct vmbus_channel *channel = context;
        u16 q_idx = channel->offermsg.offer.sub_channel_index;
        struct hv_device *device;
        struct netvsc_device *net_device;
        struct vmpacket_descriptor *desc;
        struct net_device *ndev;
        bool need_to_commit = false;

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

        ndev = hv_get_drvdata(device);
        if (unlikely(!ndev))
                return;

        net_device = net_device_to_netvsc_device(ndev);
        if (unlikely(net_device->destroy) &&
            netvsc_channel_idle(net_device, q_idx))
                return;

        /* commit_rd_index() -> hv_signal_on_read() needs this. */
        init_cached_read_index(channel);

        while ((desc = get_next_pkt_raw(channel)) != NULL) {
                netvsc_process_raw_pkt(device, channel, net_device,
                                       ndev, desc->trans_id, desc);

                put_pkt_raw(channel, desc);
                need_to_commit = true;
        }

        if (need_to_commit)
                commit_rd_index(channel);

        netvsc_chk_recv_comp(net_device, channel, q_idx);
}

/*
 * netvsc_device_add - Callback when the device belonging to this
 * driver is added
 */
int 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 -ENOMEM;

        net_device->ring_size = ring_size;

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

        /* 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.
         */
        for (i = 0; i < VRSS_CHANNEL_MAX; i++)
                net_device->chan_table[i].channel = device->channel;

        /* Writing nvdev pointer unlocks netvsc_send(), make sure chn_table is
         * populated.
         */
        wmb();

        net_device_ctx->nvdev = net_device;

        /* 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;
}