FN_VMB_PACKET_SEND_WITH_EXTERNAL_PFNS callback function (vmbuskernelmodeclientlibapi.h)

Article
04/01/2021

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The VmbPacketSendWithExternalPfns function sends the data in a packet buffer or external data as an array of Page Frame Numbers (PFNs). The function associates that data with the VMBus packet object, which represents the packet throughout the lifetime of the transaction.

Syntax

FN_VMB_PACKET_SEND_WITH_EXTERNAL_PFNS FnVmbPacketSendWithExternalPfns;

NTSTATUS FnVmbPacketSendWithExternalPfns(
  __drv_aliasesMem VMBPACKET PacketObject,
  PVOID Buffer,
  UINT32 BufferLength,
  PPFN_NUMBER ExternalDataPfns,
  UINT32 PfnLength,
  UINT32 Flags
)
{...}

Parameters

PacketObject

A handle to the VMBus packet object.

Buffer

A buffer that contains the command packet that is sent through the VMBus ring buffer.

BufferLength

The length, in bytes, of the buffer in the Buffer parameter.

ExternalDataPfns

An array of Page Frame Numbers that describe a data buffer associated with the packet.

PfnLength

The number of PFNs to send from ExternalDataPfns. The final referenced array index is ExternalDataPfns[PfnOffset+PfnLength-1] inclusive.

Flags

Flags. The following are pertinent flags:

Value	Meaning
VMBUS_CHANNEL_FORMAT_FLAG_WAIT_FOR_COMPLETION	This packet cannot be considered complete and its resources cannot be released until a completion packet comes back from the opposite endpoint. This flag must be set.
VMBUS_CHANNEL_FORMAT_FLAG_PAGED_BUFFER	The inline buffer is paged and must be treated accordingly, which means it must be copied before entering DPC level. Probing user-mode buffers or handling access violations is the responsibility of the caller.

Return value

Returns STATUS_SUCCESS if the operation succeeds, or an appropriate NTSTATUS error code otherwise.

Remarks

This function differs from the VmbPacketSend function in that it allows passing an array of PFNs, effectively physical addresses.

Important

This function is called through the VMBus Kernel Mode Client Library (KMCL) interface, provided by the Vmbkmcl.sys bus driver. This is a client function accessed from the KMCL_CLIENT_INTERFACE_V1 structure.

For more information, see the Remarks section of the KMCL_CLIENT_INTERFACE_V1.

Requirements

Requirement	Value
Minimum supported client	Windows 10, version 1803
Header	vmbuskernelmodeclientlibapi.h