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* An implementation of HyperV key value pair (KVP) functionality for Linux.
* Copyright (C) 2010, Novell, Inc.
* Author : K. Y. Srinivasan <>
* 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
* NON INFRINGEMENT. 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, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
#ifndef _KVP_H
#define _KVP_H_
* Maximum value size - used for both key names and value data, and includes
* any applicable NULL terminators.
* Note: This limit is somewhat arbitrary, but falls easily within what is
* supported for all native guests (back to Win 2000) and what is reasonable
* for the IC KVP exchange functionality. Note that Windows Me/98/95 are
* limited to 255 character key names.
* MSDN recommends not storing data values larger than 2048 bytes in the
* registry.
* Note: This value is used in defining the KVP exchange message - this value
* cannot be modified without affecting the message size and compatibility.
* bytes, including any null terminators
* Maximum key size - the registry limit for the length of an entry name
* is 256 characters, including the null terminator
* In Linux, we implement the KVP functionality in two components:
* 1) The kernel component which is packaged as part of the hv_utils driver
* is responsible for communicating with the host and responsible for
* implementing the host/guest protocol. 2) A user level daemon that is
* responsible for data gathering.
* Host/Guest Protocol: The host iterates over an index and expects the guest
* to assign a key name to the index and also return the value corresponding to
* the key. The host will have atmost one KVP transaction outstanding at any
* given point in time. The host side iteration stops when the guest returns
* an error. Microsoft has specified the following mapping of key names to
* host specified index:
* Index Key Name
* 0 FullyQualifiedDomainName
* 1 IntegrationServicesVersion
* 2 NetworkAddressIPv4
* 3 NetworkAddressIPv6
* 4 OSBuildNumber
* 5 OSName
* 6 OSMajorVersion
* 7 OSMinorVersion
* 8 OSVersion
* 9 ProcessorArchitecture
* The Windows host expects the Key Name and Key Value to be encoded in utf16.
* Guest Kernel/KVP Daemon Protocol: As noted earlier, we implement all of the
* data gathering functionality in a user mode daemon. The user level daemon
* is also responsible for binding the key name to the index as well. The
* kernel and user-level daemon communicate using a connector channel.
* The user mode component first registers with the
* the kernel component. Subsequently, the kernel component requests, data
* for the specified keys. In response to this message the user mode component
* fills in the value corresponding to the specified key. We overload the
* sequence field in the cn_msg header to define our KVP message types.
* The kernel component simply acts as a conduit for communication between the
* Windows host and the user-level daemon. The kernel component passes up the
* index received from the Host to the user-level daemon. If the index is
* valid (supported), the corresponding key as well as its
* value (both are strings) is returned. If the index is invalid
* (not supported), a NULL key string is returned.
* The following definitions are shared with the user-mode component; do not
* change any of this without making the corresponding changes in
* the KVP user-mode component.
#define CN_KVP_VAL 0x1 /* This supports queries from the kernel */
#define CN_KVP_USER_VAL 0x2 /* This supports queries from the user */
enum hv_ku_op {
KVP_REGISTER = 0, /* Register the user mode component */
KVP_KERNEL_GET, /* Kernel is requesting the value */
KVP_KERNEL_SET, /* Kernel is providing the value */
KVP_USER_GET, /* User is requesting the value */
KVP_USER_SET /* User is providing the value */
struct hv_ku_msg {
__u32 kvp_index; /* Key index */
__u8 kvp_key[HV_KVP_EXCHANGE_MAX_KEY_SIZE]; /* Key name */
__u8 kvp_value[HV_KVP_EXCHANGE_MAX_VALUE_SIZE]; /* Key value */
#ifdef __KERNEL__
* Registry value types.
#define REG_SZ 1
enum hv_kvp_exchg_op {
KVP_OP_COUNT /* Number of operations, must be last. */
enum hv_kvp_exchg_pool {
KVP_POOL_COUNT /* Number of pools, must be last. */
struct hv_kvp_hdr {
u8 operation;
u8 pool;
struct hv_kvp_exchg_msg_value {
u32 value_type;
u32 key_size;
u32 value_size;
struct hv_kvp_msg_enumerate {
u32 index;
struct hv_kvp_exchg_msg_value data;
struct hv_kvp_msg {
struct hv_kvp_hdr kvp_hdr;
struct hv_kvp_msg_enumerate kvp_data;
int hv_kvp_init(struct hv_util_service *);
void hv_kvp_deinit(void);
void hv_kvp_onchannelcallback(void *);
#endif /* __KERNEL__ */
#endif /* _KVP_H */