The HvCallPostMessage hypercall attempts to post (that is, send asynchronously) a message to the specified connection, which has an associated destination port. If the message is successfully posted, then it will be queued for delivery to a virtual processor within the partition associated with the port.


   _In_ HV_CONNECTION_ID ConnectionId,
   _In_ HV_MESSAGE_TYPE MessageType,
   _In_ UINT32 PayloadSize,
   _In_reads_bytes_(PayloadSize) PCVOID Message

Call Code

0x005C (Simple)

Input Parameters

Name Offset Size Information Provided
ConnectionId 0 4 Specifies the ID of the connection.
RsvdZ 4 4
MessageType 8 4 Specifies the message type that will appear within the message header. The caller can specify any 32-bit message type whose most significant bit is cleared, with the exception of zero.
PayloadSize 12 4 Specifies the number of bytes that are included in the message.
Message 16 240 Secifies the payload of the message—up to 240 bytes total. Only the first n bytes are actually sent to the destination partition, where n is provided in the PayloadSize parameter.

Return Values

Status code Error Condition
HV_STATUS_ACCESS_DENIED The caller’s partition does not possess the PostMessages privilege.
HV_STATUS_INVALID_CONNECTION_ID The specified connection ID is invalid.
HV_STATUS_INVALID_PORT_ID The port associated with the specified connection has been deleted.
The port associated with the specified connection belongs to a partition that is not in the “active” state.
The port associated with the specified connection is not a "message" type port.
HV_STATUS_INVALID_PARAMETER The most significant bit of the specified message type is set.
The MessageType parameter specifies a value of zero.
The specified payload size exceeds 240 bytes.
HV_STATUS_INSUFFICIENT_BUFFERS The port has no available guest message buffers.
HV_STATUS_INVALID_VP_INDEX The target VP no longer exists or there are no available VPs to which the message can be posted.
HV_STATUS_INVALID_SYNIC_STATE The target VP’s SynIC is disabled and cannot accept posted messages.
The target VP’s SIM page is disabled.