1 files changed, 1041 insertions, 0 deletions

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
new file mode 100644
index 000000000000..bbc497373aaf
--- /dev/null
+++ b/drivers/hv/hv_balloon.c
@@ -0,0 +1,1041 @@
+/*
+ * Copyright (c) 2012, Microsoft Corporation.
+ *
+ * Author:
+ *   K. Y. Srinivasan <kys@microsoft.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/mman.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kthread.h>
+#include <linux/completion.h>
+#include <linux/memory_hotplug.h>
+#include <linux/memory.h>
+#include <linux/notifier.h>
+#include <linux/mman.h>
+#include <linux/percpu_counter.h>
+
+#include <linux/hyperv.h>
+
+/*
+ * We begin with definitions supporting the Dynamic Memory protocol
+ * with the host.
+ *
+ * Begin protocol definitions.
+ */
+
+
+
+/*
+ * Protocol versions. The low word is the minor version, the high word the major
+ * version.
+ *
+ * History:
+ * Initial version 1.0
+ * Changed to 0.1 on 2009/03/25
+ * Changes to 0.2 on 2009/05/14
+ * Changes to 0.3 on 2009/12/03
+ * Changed to 1.0 on 2011/04/05
+ */
+
+#define DYNMEM_MAKE_VERSION(Major, Minor) ((__u32)(((Major) << 16) | (Minor)))
+#define DYNMEM_MAJOR_VERSION(Version) ((__u32)(Version) >> 16)
+#define DYNMEM_MINOR_VERSION(Version) ((__u32)(Version) & 0xff)
+
+enum {
+        DYNMEM_PROTOCOL_VERSION_1 = DYNMEM_MAKE_VERSION(0, 3),
+        DYNMEM_PROTOCOL_VERSION_2 = DYNMEM_MAKE_VERSION(1, 0),
+
+        DYNMEM_PROTOCOL_VERSION_WIN7 = DYNMEM_PROTOCOL_VERSION_1,
+        DYNMEM_PROTOCOL_VERSION_WIN8 = DYNMEM_PROTOCOL_VERSION_2,
+
+        DYNMEM_PROTOCOL_VERSION_CURRENT = DYNMEM_PROTOCOL_VERSION_WIN8
+};
+
+
+
+/*
+ * Message Types
+ */
+
+enum dm_message_type {
+        /*
+         * Version 0.3
+         */
+        DM_ERROR                        = 0,
+        DM_VERSION_REQUEST              = 1,
+        DM_VERSION_RESPONSE             = 2,
+        DM_CAPABILITIES_REPORT          = 3,
+        DM_CAPABILITIES_RESPONSE        = 4,
+        DM_STATUS_REPORT                = 5,
+        DM_BALLOON_REQUEST              = 6,
+        DM_BALLOON_RESPONSE             = 7,
+        DM_UNBALLOON_REQUEST            = 8,
+        DM_UNBALLOON_RESPONSE           = 9,
+        DM_MEM_HOT_ADD_REQUEST          = 10,
+        DM_MEM_HOT_ADD_RESPONSE         = 11,
+        DM_VERSION_03_MAX               = 11,
+        /*
+         * Version 1.0.
+         */
+        DM_INFO_MESSAGE                 = 12,
+        DM_VERSION_1_MAX                = 12
+};
+
+
+/*
+ * Structures defining the dynamic memory management
+ * protocol.
+ */
+
+union dm_version {
+        struct {
+                __u16 minor_version;
+                __u16 major_version;
+        };
+        __u32 version;
+} __packed;
+
+
+union dm_caps {
+        struct {
+                __u64 balloon:1;
+                __u64 hot_add:1;
+                __u64 reservedz:62;
+        } cap_bits;
+        __u64 caps;
+} __packed;
+
+union dm_mem_page_range {
+        struct  {
+                /*
+                 * The PFN number of the first page in the range.
+                 * 40 bits is the architectural limit of a PFN
+                 * number for AMD64.
+                 */
+                __u64 start_page:40;
+                /*
+                 * The number of pages in the range.
+                 */
+                __u64 page_cnt:24;
+        } finfo;
+        __u64  page_range;
+} __packed;
+
+
+
+/*
+ * The header for all dynamic memory messages:
+ *
+ * type: Type of the message.
+ * size: Size of the message in bytes; including the header.
+ * trans_id: The guest is responsible for manufacturing this ID.
+ */
+
+struct dm_header {
+        __u16 type;
+        __u16 size;
+        __u32 trans_id;
+} __packed;
+
+/*
+ * A generic message format for dynamic memory.
+ * Specific message formats are defined later in the file.
+ */
+
+struct dm_message {
+        struct dm_header hdr;
+        __u8 data[]; /* enclosed message */
+} __packed;
+
+
+/*
+ * Specific message types supporting the dynamic memory protocol.
+ */
+
+/*
+ * Version negotiation message. Sent from the guest to the host.
+ * The guest is free to try different versions until the host
+ * accepts the version.
+ *
+ * dm_version: The protocol version requested.
+ * is_last_attempt: If TRUE, this is the last version guest will request.
+ * reservedz: Reserved field, set to zero.
+ */
+
+struct dm_version_request {
+        struct dm_header hdr;
+        union dm_version version;
+        __u32 is_last_attempt:1;
+        __u32 reservedz:31;
+} __packed;
+
+/*
+ * Version response message; Host to Guest and indicates
+ * if the host has accepted the version sent by the guest.
+ *
+ * is_accepted: If TRUE, host has accepted the version and the guest
+ * should proceed to the next stage of the protocol. FALSE indicates that
+ * guest should re-try with a different version.
+ *
+ * reservedz: Reserved field, set to zero.
+ */
+
+struct dm_version_response {
+        struct dm_header hdr;
+        __u64 is_accepted:1;
+        __u64 reservedz:63;
+} __packed;
+
+/*
+ * Message reporting capabilities. This is sent from the guest to the
+ * host.
+ */
+
+struct dm_capabilities {
+        struct dm_header hdr;
+        union dm_caps caps;
+        __u64 min_page_cnt;
+        __u64 max_page_number;
+} __packed;
+
+/*
+ * Response to the capabilities message. This is sent from the host to the
+ * guest. This message notifies if the host has accepted the guest's
+ * capabilities. If the host has not accepted, the guest must shutdown
+ * the service.
+ *
+ * is_accepted: Indicates if the host has accepted guest's capabilities.
+ * reservedz: Must be 0.
+ */
+
+struct dm_capabilities_resp_msg {
+        struct dm_header hdr;
+        __u64 is_accepted:1;
+        __u64 reservedz:63;
+} __packed;
+
+/*
+ * This message is used to report memory pressure from the guest.
+ * This message is not part of any transaction and there is no
+ * response to this message.
+ *
+ * num_avail: Available memory in pages.
+ * num_committed: Committed memory in pages.
+ * page_file_size: The accumulated size of all page files
+ *                 in the system in pages.
+ * zero_free: The nunber of zero and free pages.
+ * page_file_writes: The writes to the page file in pages.
+ * io_diff: An indicator of file cache efficiency or page file activity,
+ *          calculated as File Cache Page Fault Count - Page Read Count.
+ *          This value is in pages.
+ *
+ * Some of these metrics are Windows specific and fortunately
+ * the algorithm on the host side that computes the guest memory
+ * pressure only uses num_committed value.
+ */
+
+struct dm_status {
+        struct dm_header hdr;
+        __u64 num_avail;
+        __u64 num_committed;
+        __u64 page_file_size;
+        __u64 zero_free;
+        __u32 page_file_writes;
+        __u32 io_diff;
+} __packed;
+
+
+/*
+ * Message to ask the guest to allocate memory - balloon up message.
+ * This message is sent from the host to the guest. The guest may not be
+ * able to allocate as much memory as requested.
+ *
+ * num_pages: number of pages to allocate.
+ */
+
+struct dm_balloon {
+        struct dm_header hdr;
+        __u32 num_pages;
+        __u32 reservedz;
+} __packed;
+
+
+/*
+ * Balloon response message; this message is sent from the guest
+ * to the host in response to the balloon message.
+ *
+ * reservedz: Reserved; must be set to zero.
+ * more_pages: If FALSE, this is the last message of the transaction.
+ * if TRUE there will atleast one more message from the guest.
+ *
+ * range_count: The number of ranges in the range array.
+ *
+ * range_array: An array of page ranges returned to the host.
+ *
+ */
+
+struct dm_balloon_response {
+        struct dm_header hdr;
+        __u32 reservedz;
+        __u32 more_pages:1;
+        __u32 range_count:31;
+        union dm_mem_page_range range_array[];
+} __packed;
+
+/*
+ * Un-balloon message; this message is sent from the host
+ * to the guest to give guest more memory.
+ *
+ * more_pages: If FALSE, this is the last message of the transaction.
+ * if TRUE there will atleast one more message from the guest.
+ *
+ * reservedz: Reserved; must be set to zero.
+ *
+ * range_count: The number of ranges in the range array.
+ *
+ * range_array: An array of page ranges returned to the host.
+ *
+ */
+
+struct dm_unballoon_request {
+        struct dm_header hdr;
+        __u32 more_pages:1;
+        __u32 reservedz:31;
+        __u32 range_count;
+        union dm_mem_page_range range_array[];
+} __packed;
+
+/*
+ * Un-balloon response message; this message is sent from the guest
+ * to the host in response to an unballoon request.
+ *
+ */
+
+struct dm_unballoon_response {
+        struct dm_header hdr;
+} __packed;
+
+
+/*
+ * Hot add request message. Message sent from the host to the guest.
+ *
+ * mem_range: Memory range to hot add.
+ *
+ * On Linux we currently don't support this since we cannot hot add
+ * arbitrary granularity of memory.
+ */
+
+struct dm_hot_add {
+        struct dm_header hdr;
+        union dm_mem_page_range range;
+} __packed;
+
+/*
+ * Hot add response message.
+ * This message is sent by the guest to report the status of a hot add request.
+ * If page_count is less than the requested page count, then the host should
+ * assume all further hot add requests will fail, since this indicates that
+ * the guest has hit an upper physical memory barrier.
+ *
+ * Hot adds may also fail due to low resources; in this case, the guest must
+ * not complete this message until the hot add can succeed, and the host must
+ * not send a new hot add request until the response is sent.
+ * If VSC fails to hot add memory DYNMEM_NUMBER_OF_UNSUCCESSFUL_HOTADD_ATTEMPTS
+ * times it fails the request.
+ *
+ *
+ * page_count: number of pages that were successfully hot added.
+ *
+ * result: result of the operation 1: success, 0: failure.
+ *
+ */
+
+struct dm_hot_add_response {
+        struct dm_header hdr;
+        __u32 page_count;
+        __u32 result;
+} __packed;
+
+/*
+ * Types of information sent from host to the guest.
+ */
+
+enum dm_info_type {
+        INFO_TYPE_MAX_PAGE_CNT = 0,
+        MAX_INFO_TYPE
+};
+
+
+/*
+ * Header for the information message.
+ */
+
+struct dm_info_header {
+        enum dm_info_type type;
+        __u32 data_size;
+} __packed;
+
+/*
+ * This message is sent from the host to the guest to pass
+ * some relevant information (win8 addition).
+ *
+ * reserved: no used.
+ * info_size: size of the information blob.
+ * info: information blob.
+ */
+
+struct dm_info_msg {
+        struct dm_info_header header;
+        __u32 reserved;
+        __u32 info_size;
+        __u8  info[];
+};
+
+/*
+ * End protocol definitions.
+ */
+
+static bool hot_add;
+static bool do_hot_add;
+
+module_param(hot_add, bool, (S_IRUGO | S_IWUSR));
+MODULE_PARM_DESC(hot_add, "If set attempt memory hot_add");
+
+static atomic_t trans_id = ATOMIC_INIT(0);
+
+static int dm_ring_size = (5 * PAGE_SIZE);
+
+/*
+ * Driver specific state.
+ */
+
+enum hv_dm_state {
+        DM_INITIALIZING = 0,
+        DM_INITIALIZED,
+        DM_BALLOON_UP,
+        DM_BALLOON_DOWN,
+        DM_HOT_ADD,
+        DM_INIT_ERROR
+};
+
+
+static __u8 recv_buffer[PAGE_SIZE];
+static __u8 *send_buffer;
+#define PAGES_IN_2M     512
+
+struct hv_dynmem_device {
+        struct hv_device *dev;
+        enum hv_dm_state state;
+        struct completion host_event;
+        struct completion config_event;
+
+        /*
+         * Number of pages we have currently ballooned out.
+         */
+        unsigned int num_pages_ballooned;
+
+        /*
+         * This thread handles both balloon/hot-add
+         * requests from the host as well as notifying
+         * the host with regards to memory pressure in
+         * the guest.
+         */
+        struct task_struct *thread;
+
+        /*
+         * We start with the highest version we can support
+         * and downgrade based on the host; we save here the
+         * next version to try.
+         */
+        __u32 next_version;
+};
+
+static struct hv_dynmem_device dm_device;
+
+static void hot_add_req(struct hv_dynmem_device *dm, struct dm_hot_add *msg)
+{
+
+        struct dm_hot_add_response resp;
+
+        if (do_hot_add) {
+
+                pr_info("Memory hot add not supported\n");
+
+                /*
+                 * Currently we do not support hot add.
+                 * Just fail the request.
+                 */
+        }
+
+        memset(&resp, 0, sizeof(struct dm_hot_add_response));
+        resp.hdr.type = DM_MEM_HOT_ADD_RESPONSE;
+        resp.hdr.size = sizeof(struct dm_hot_add_response);
+        resp.hdr.trans_id = atomic_inc_return(&trans_id);
+
+        resp.page_count = 0;
+        resp.result = 0;
+
+        dm->state = DM_INITIALIZED;
+        vmbus_sendpacket(dm->dev->channel, &resp,
+                        sizeof(struct dm_hot_add_response),
+                        (unsigned long)NULL,
+                        VM_PKT_DATA_INBAND, 0);
+
+}
+
+static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
+{
+        switch (msg->header.type) {
+        case INFO_TYPE_MAX_PAGE_CNT:
+                pr_info("Received INFO_TYPE_MAX_PAGE_CNT\n");
+                pr_info("Data Size is %d\n", msg->header.data_size);
+                break;
+        default:
+                pr_info("Received Unknown type: %d\n", msg->header.type);
+        }
+}
+
+/*
+ * Post our status as it relates memory pressure to the
+ * host. Host expects the guests to post this status
+ * periodically at 1 second intervals.
+ *
+ * The metrics specified in this protocol are very Windows
+ * specific and so we cook up numbers here to convey our memory
+ * pressure.
+ */
+
+static void post_status(struct hv_dynmem_device *dm)
+{
+        struct dm_status status;
+
+
+        memset(&status, 0, sizeof(struct dm_status));
+        status.hdr.type = DM_STATUS_REPORT;
+        status.hdr.size = sizeof(struct dm_status);
+        status.hdr.trans_id = atomic_inc_return(&trans_id);
+
+
+        status.num_committed = vm_memory_committed();
+
+        vmbus_sendpacket(dm->dev->channel, &status,
+                                sizeof(struct dm_status),
+                                (unsigned long)NULL,
+                                VM_PKT_DATA_INBAND, 0);
+
+}
+
+
+
+void free_balloon_pages(struct hv_dynmem_device *dm,
+                         union dm_mem_page_range *range_array)
+{
+        int num_pages = range_array->finfo.page_cnt;
+        __u64 start_frame = range_array->finfo.start_page;
+        struct page *pg;
+        int i;
+
+        for (i = 0; i < num_pages; i++) {
+                pg = pfn_to_page(i + start_frame);
+                __free_page(pg);
+                dm->num_pages_ballooned--;
+        }
+}
+
+
+
+static int  alloc_balloon_pages(struct hv_dynmem_device *dm, int num_pages,
+                         struct dm_balloon_response *bl_resp, int alloc_unit,
+                         bool *alloc_error)
+{
+        int i = 0;
+        struct page *pg;
+
+        if (num_pages < alloc_unit)
+                return 0;
+
+        for (i = 0; (i * alloc_unit) < num_pages; i++) {
+                if (bl_resp->hdr.size + sizeof(union dm_mem_page_range) >
+                        PAGE_SIZE)
+                        return i * alloc_unit;
+
+                /*
+                 * We execute this code in a thread context. Furthermore,
+                 * we don't want the kernel to try too hard.
+                 */
+                pg = alloc_pages(GFP_HIGHUSER | __GFP_NORETRY |
+                                __GFP_NOMEMALLOC | __GFP_NOWARN,
+                                get_order(alloc_unit << PAGE_SHIFT));
+
+                if (!pg) {
+                        *alloc_error = true;
+                        return i * alloc_unit;
+                }
+
+
+                dm->num_pages_ballooned += alloc_unit;
+
+                bl_resp->range_count++;
+                bl_resp->range_array[i].finfo.start_page =
+                        page_to_pfn(pg);
+                bl_resp->range_array[i].finfo.page_cnt = alloc_unit;
+                bl_resp->hdr.size += sizeof(union dm_mem_page_range);
+
+        }
+
+        return num_pages;
+}
+
+
+
+static void balloon_up(struct hv_dynmem_device *dm, struct dm_balloon *req)
+{
+        int num_pages = req->num_pages;
+        int num_ballooned = 0;
+        struct dm_balloon_response *bl_resp;
+        int alloc_unit;
+        int ret;
+        bool alloc_error = false;
+        bool done = false;
+        int i;
+
+
+        /*
+         * Currently, we only support 4k allocations.
+         */
+        alloc_unit = 1;
+
+        while (!done) {
+                bl_resp = (struct dm_balloon_response *)send_buffer;
+                memset(send_buffer, 0, PAGE_SIZE);
+                bl_resp->hdr.type = DM_BALLOON_RESPONSE;
+                bl_resp->hdr.trans_id = atomic_inc_return(&trans_id);
+                bl_resp->hdr.size = sizeof(struct dm_balloon_response);
+                bl_resp->more_pages = 1;
+
+
+                num_pages -= num_ballooned;
+                num_ballooned = alloc_balloon_pages(dm, num_pages,
+                                                bl_resp, alloc_unit,
+                                                 &alloc_error);
+
+                if ((alloc_error) || (num_ballooned == num_pages)) {
+                        bl_resp->more_pages = 0;
+                        done = true;
+                        dm->state = DM_INITIALIZED;
+                }
+
+                /*
+                 * We are pushing a lot of data through the channel;
+                 * deal with transient failures caused because of the
+                 * lack of space in the ring buffer.
+                 */
+
+                do {
+                        ret = vmbus_sendpacket(dm_device.dev->channel,
+                                                bl_resp,
+                                                bl_resp->hdr.size,
+                                                (unsigned long)NULL,
+                                                VM_PKT_DATA_INBAND, 0);
+
+                        if (ret == -EAGAIN)
+                                msleep(20);
+
+                } while (ret == -EAGAIN);
+
+                if (ret) {
+                        /*
+                         * Free up the memory we allocatted.
+                         */
+                        pr_info("Balloon response failed\n");
+
+                        for (i = 0; i < bl_resp->range_count; i++)
+                                free_balloon_pages(dm,
+                                                 &bl_resp->range_array[i]);
+
+                        done = true;
+                }
+        }
+
+}
+
+static void balloon_down(struct hv_dynmem_device *dm,
+                        struct dm_unballoon_request *req)
+{
+        union dm_mem_page_range *range_array = req->range_array;
+        int range_count = req->range_count;
+        struct dm_unballoon_response resp;
+        int i;
+
+        for (i = 0; i < range_count; i++)
+                free_balloon_pages(dm, &range_array[i]);
+
+        if (req->more_pages == 1)
+                return;
+
+        memset(&resp, 0, sizeof(struct dm_unballoon_response));
+        resp.hdr.type = DM_UNBALLOON_RESPONSE;
+        resp.hdr.trans_id = atomic_inc_return(&trans_id);
+        resp.hdr.size = sizeof(struct dm_unballoon_response);
+
+        vmbus_sendpacket(dm_device.dev->channel, &resp,
+                                sizeof(struct dm_unballoon_response),
+                                (unsigned long)NULL,
+                                VM_PKT_DATA_INBAND, 0);
+
+        dm->state = DM_INITIALIZED;
+}
+
+static void balloon_onchannelcallback(void *context);
+
+static int dm_thread_func(void *dm_dev)
+{
+        struct hv_dynmem_device *dm = dm_dev;
+        int t;
+        unsigned long  scan_start;
+
+        while (!kthread_should_stop()) {
+                t = wait_for_completion_timeout(&dm_device.config_event, 1*HZ);
+                /*
+                 * The host expects us to post information on the memory
+                 * pressure every second.
+                 */
+
+                if (t == 0)
+                        post_status(dm);
+
+                scan_start = jiffies;
+                switch (dm->state) {
+                case DM_BALLOON_UP:
+                        balloon_up(dm, (struct dm_balloon *)recv_buffer);
+                        break;
+
+                case DM_HOT_ADD:
+                        hot_add_req(dm, (struct dm_hot_add *)recv_buffer);
+                        break;
+                default:
+                        break;
+                }
+
+                if (!time_in_range(jiffies, scan_start, scan_start + HZ))
+                        post_status(dm);
+
+        }
+
+        return 0;
+}
+
+
+static void version_resp(struct hv_dynmem_device *dm,
+                        struct dm_version_response *vresp)
+{
+        struct dm_version_request version_req;
+        int ret;
+
+        if (vresp->is_accepted) {
+                /*
+                 * We are done; wakeup the
+                 * context waiting for version
+                 * negotiation.
+                 */
+                complete(&dm->host_event);
+                return;
+        }
+        /*
+         * If there are more versions to try, continue
+         * with negotiations; if not
+         * shutdown the service since we are not able
+         * to negotiate a suitable version number
+         * with the host.
+         */
+        if (dm->next_version == 0)
+                goto version_error;
+
+        dm->next_version = 0;
+        memset(&version_req, 0, sizeof(struct dm_version_request));
+        version_req.hdr.type = DM_VERSION_REQUEST;
+        version_req.hdr.size = sizeof(struct dm_version_request);
+        version_req.hdr.trans_id = atomic_inc_return(&trans_id);
+        version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN7;
+        version_req.is_last_attempt = 1;
+
+        ret = vmbus_sendpacket(dm->dev->channel, &version_req,
+                                sizeof(struct dm_version_request),
+                                (unsigned long)NULL,
+                                VM_PKT_DATA_INBAND, 0);
+
+        if (ret)
+                goto version_error;
+
+        return;
+
+version_error:
+        dm->state = DM_INIT_ERROR;
+        complete(&dm->host_event);
+}
+
+static void cap_resp(struct hv_dynmem_device *dm,
+                        struct dm_capabilities_resp_msg *cap_resp)
+{
+        if (!cap_resp->is_accepted) {
+                pr_info("Capabilities not accepted by host\n");
+                dm->state = DM_INIT_ERROR;
+        }
+        complete(&dm->host_event);
+}
+
+static void balloon_onchannelcallback(void *context)
+{
+        struct hv_device *dev = context;
+        u32 recvlen;
+        u64 requestid;
+        struct dm_message *dm_msg;
+        struct dm_header *dm_hdr;
+        struct hv_dynmem_device *dm = hv_get_drvdata(dev);
+
+        memset(recv_buffer, 0, sizeof(recv_buffer));
+        vmbus_recvpacket(dev->channel, recv_buffer,
+                         PAGE_SIZE, &recvlen, &requestid);
+
+        if (recvlen > 0) {
+                dm_msg = (struct dm_message *)recv_buffer;
+                dm_hdr = &dm_msg->hdr;
+
+                switch (dm_hdr->type) {
+                case DM_VERSION_RESPONSE:
+                        version_resp(dm,
+                                 (struct dm_version_response *)dm_msg);
+                        break;
+
+                case DM_CAPABILITIES_RESPONSE:
+                        cap_resp(dm,
+                                 (struct dm_capabilities_resp_msg *)dm_msg);
+                        break;
+
+                case DM_BALLOON_REQUEST:
+                        dm->state = DM_BALLOON_UP;
+                        complete(&dm->config_event);
+                        break;
+
+                case DM_UNBALLOON_REQUEST:
+                        dm->state = DM_BALLOON_DOWN;
+                        balloon_down(dm,
+                                 (struct dm_unballoon_request *)recv_buffer);
+                        break;
+
+                case DM_MEM_HOT_ADD_REQUEST:
+                        dm->state = DM_HOT_ADD;
+                        complete(&dm->config_event);
+                        break;
+
+                case DM_INFO_MESSAGE:
+                        process_info(dm, (struct dm_info_msg *)dm_msg);
+                        break;
+
+                default:
+                        pr_err("Unhandled message: type: %d\n", dm_hdr->type);
+
+                }
+        }
+
+}
+
+static int balloon_probe(struct hv_device *dev,
+                        const struct hv_vmbus_device_id *dev_id)
+{
+        int ret, t;
+        struct dm_version_request version_req;
+        struct dm_capabilities cap_msg;
+
+        do_hot_add = hot_add;
+
+        /*
+         * First allocate a send buffer.
+         */
+
+        send_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!send_buffer)
+                return -ENOMEM;
+
+        ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0,
+                        balloon_onchannelcallback, dev);
+
+        if (ret)
+                return ret;
+
+        dm_device.dev = dev;
+        dm_device.state = DM_INITIALIZING;
+        dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
+        init_completion(&dm_device.host_event);
+        init_completion(&dm_device.config_event);
+
+        dm_device.thread =
+                 kthread_run(dm_thread_func, &dm_device, "hv_balloon");
+        if (IS_ERR(dm_device.thread)) {
+                ret = PTR_ERR(dm_device.thread);
+                goto probe_error0;
+        }
+
+        hv_set_drvdata(dev, &dm_device);
+        /*
+         * Initiate the hand shake with the host and negotiate
+         * a version that the host can support. We start with the
+         * highest version number and go down if the host cannot
+         * support it.
+         */
+        memset(&version_req, 0, sizeof(struct dm_version_request));
+        version_req.hdr.type = DM_VERSION_REQUEST;
+        version_req.hdr.size = sizeof(struct dm_version_request);
+        version_req.hdr.trans_id = atomic_inc_return(&trans_id);
+        version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN8;
+        version_req.is_last_attempt = 0;
+
+        ret = vmbus_sendpacket(dev->channel, &version_req,
+                                sizeof(struct dm_version_request),
+                                (unsigned long)NULL,
+                                VM_PKT_DATA_INBAND,
+                                VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+        if (ret)
+                goto probe_error1;
+
+        t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
+        if (t == 0) {
+                ret = -ETIMEDOUT;
+                goto probe_error1;
+        }
+
+        /*
+         * If we could not negotiate a compatible version with the host
+         * fail the probe function.
+         */
+        if (dm_device.state == DM_INIT_ERROR) {
+                ret = -ETIMEDOUT;
+                goto probe_error1;
+        }
+        /*
+         * Now submit our capabilities to the host.
+         */
+        memset(&cap_msg, 0, sizeof(struct dm_capabilities));
+        cap_msg.hdr.type = DM_CAPABILITIES_REPORT;
+        cap_msg.hdr.size = sizeof(struct dm_capabilities);
+        cap_msg.hdr.trans_id = atomic_inc_return(&trans_id);
+
+        cap_msg.caps.cap_bits.balloon = 1;
+        /*
+         * While we currently don't support hot-add,
+         * we still advertise this capability since the
+         * host requires that guests partcipating in the
+         * dynamic memory protocol support hot add.
+         */
+        cap_msg.caps.cap_bits.hot_add = 1;
+
+        /*
+         * Currently the host does not use these
+         * values and we set them to what is done in the
+         * Windows driver.
+         */
+        cap_msg.min_page_cnt = 0;
+        cap_msg.max_page_number = -1;
+
+        ret = vmbus_sendpacket(dev->channel, &cap_msg,
+                                sizeof(struct dm_capabilities),
+                                (unsigned long)NULL,
+                                VM_PKT_DATA_INBAND,
+                                VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+        if (ret)
+                goto probe_error1;
+
+        t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
+        if (t == 0) {
+                ret = -ETIMEDOUT;
+                goto probe_error1;
+        }
+
+        /*
+         * If the host does not like our capabilities,
+         * fail the probe function.
+         */
+        if (dm_device.state == DM_INIT_ERROR) {
+                ret = -ETIMEDOUT;
+                goto probe_error1;
+        }
+
+        dm_device.state = DM_INITIALIZED;
+
+        return 0;
+
+probe_error1:
+        kthread_stop(dm_device.thread);
+
+probe_error0:
+        vmbus_close(dev->channel);
+        return ret;
+}
+
+static int balloon_remove(struct hv_device *dev)
+{
+        struct hv_dynmem_device *dm = hv_get_drvdata(dev);
+
+        if (dm->num_pages_ballooned != 0)
+                pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
+
+        vmbus_close(dev->channel);
+        kthread_stop(dm->thread);
+
+        return 0;
+}
+
+static const struct hv_vmbus_device_id id_table[] = {
+        /* Dynamic Memory Class ID */
+        /* 525074DC-8985-46e2-8057-A307DC18A502 */
+        { VMBUS_DEVICE(0xdc, 0x74, 0x50, 0X52, 0x85, 0x89, 0xe2, 0x46,
+                       0x80, 0x57, 0xa3, 0x07, 0xdc, 0x18, 0xa5, 0x02)
+        },
+        { },
+};
+
+MODULE_DEVICE_TABLE(vmbus, id_table);
+
+static  struct hv_driver balloon_drv = {
+        .name = "hv_balloon",
+        .id_table = id_table,
+        .probe =  balloon_probe,
+        .remove =  balloon_remove,
+};
+
+static int __init init_balloon_drv(void)
+{
+
+        return vmbus_driver_register(&balloon_drv);
+}
+
+static void exit_balloon_drv(void)
+{
+
+        vmbus_driver_unregister(&balloon_drv);
+}
+
+module_init(init_balloon_drv);
+module_exit(exit_balloon_drv);
+
+MODULE_DESCRIPTION("Hyper-V Balloon");
+MODULE_VERSION(HV_DRV_VERSION);
+MODULE_LICENSE("GPL");