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Windows Driver Kit DDI reference (nc-vmbuskernelmodeclientlibapi-fn_vmb_server_channel_init_set_mmio_megabytes)

FN_VMB_SERVER_CHANNEL_INIT_SET_MMIO_MEGABYTES callback function

Description

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

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

Prototype

//Declaration

FN_VMB_SERVER_CHANNEL_INIT_SET_MMIO_MEGABYTES FnVmbServerChannelInitSetMmioMegabytes;

// Definition

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

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.

FN_VMB_SERVER_CHANNEL_INIT_SET_MMIO_MEGABYTES - NtDoc