Edit

FN_VMB_SERVER_CHANNEL_INIT_SET_MMIO_MEGABYTES callback function (vmbuskernelmodeclientlibapi.h)

  • Article

The VmbServerChannelInitSetMmioMegabytes function specifies the amount, megabytes, of guest memory-mapped I/O (MMIO) space to reserve for the device.

Syntax

FN_VMB_SERVER_CHANNEL_INIT_SET_MMIO_MEGABYTES FnVmbServerChannelInitSetMmioMegabytes;

NTSTATUS FnVmbServerChannelInitSetMmioMegabytes(
  VMBCHANNEL Channel,
  UINT16 MmioMegabytes,
  UINT16 MmioMegabytesOptional
)
{...}

Parameters

Channel

A handle for a channel.

MmioMegabytes

The amount of MMIO space, in megabytes, to reserve.

MmioMegabytesOptional

The amount of extra optional MMIO space, in megabytes, to reserve.

Return value

VmbServerChannelInitSetMmioMegabytes returns the following status values:

Return code Description
STATUS_INVALID_PARAMETER_1
 The Channel value was invalid or in an invalid state, such as Disabled.
STATUS_INVALID_PARAMETER
 Both MmioMegabytes and MmioMegabytesOptional have a value of zero (0). One of these parameters must be greater than zero

Remarks

This function exists as a convenience for driver creators. Everything it does could be done by interacting the with the guest plug-and-play manager and requesting memory-mapped I/O space directly. It is a common requirement that the Windows and Linux VMBus drivers have the capacity to reserve MMIO space on behalf of the client. This function allows the server endpoint to suggest the right amount of MMIO space to reserve.

Important

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

For more information, see the Remarks section of KMCL_SERVER_ONLY_METHODS.

Requirements

Requirement Value
Minimum supported client Windows 10, version 1809
Header vmbuskernelmodeclientlibapi.h