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include vmm.inc
 
VMMcall _MapIntoV86, <hMem, VM, VMLinPgNum, nPages, PageOff, flags>
 
or      eax, eax            ; nonzero if pages mapped, zero if error
jz      not_mapped
 
The _MapIntoV86 service maps one or more pages of a memory block into the
V86 address space of the specified virtual machine.
 
Parameter   Description
────────────────────────────────────────────────────────────────────────────
 
hMem        Specifies the handle identifying the memory block to map. This
            handle must have been previously created using the PageAllocate
            or PageReAllocate service.
 
VM          Specifies a handle identifying the virtual machine for which to
            map the memory.
 
VMLinPgNum  Specifies the linear page number of a V86 address. The service
            maps the specified pages to this address. This parameter must be
            a page number in the range 10h through 10Fh.
 
nPages      Specifies the number of pages to map.
 
PageOff     Specifies the offset in pages from the beginning of the memory
            block to the first page to map.
 
flags       Specifies the operation flags. This parameter can be the
            following value:
 
            Value              Meaning
            ────────────────────────────────────────────────────────────────
            PageDEBUGNulFault  Enables page faults for system nul pages. If
                               the memory block contains system nul pages, a
                               page fault occurs whenever a nul page is
                               accessed. This value only applies when
                               running the debugging version of the Windows
                               virtual machine manager. If this value is not
                               given or the debugging version is not
                               running, no page faults occur.
 
            All other values are reserved.
 
Return Value
 
The EAX register contains a nonzero value if the map is successful.
Otherwise, EAX contains zero to indicate an error such as an invalid memory
handle, an invalid virtual machine handle, an illegal map range, a size
discrepancy, or insufficient memory for locking.
 
Comments
 
A virtual device typically uses this service to map buffers having
protected-mode addresses into the V86 address space. This gives software
running in the virtual machine a means of passing data to and receiving data
from the virtual device.
 
The service returns an error if the sum of the PageOff and nPages parameters
is greater than the size of the memory block.
 
Although a virtual device can map the same page into multiple addresses in
the V86 address space, this is not recommended.
 
For each mapped page, this service sets the P_USER, P_PRES, and P_WRITE bits
but clears the P_DIRTY and P_ACC bits. The service sets the page type to be
identical to the page type for the pages at the specified protected-mode
linear address. Although the memory block to be mapped can have PG_SYS page
type, it is not recommended.
 
If the virtual pageswap device uses MS-DOS or BIOS functions to write to the
hardware, _MapIntoV86 automatically locks the mapped pages and unlocks any
previously mapped pages. If the virtual pageswap device writes directly to
the hardware, this service neither lock nor unlocks the pages.
 
If a virtual device no longer needs the mapped region, it should map the
system nul page into the V86 address space using the _MapIntoV86 service. A
virtual device can retrieve the handle for the system nul page using the
_GetNulPageHandle service.
 
This service accepts V86 page numbers between 10h and the page number
returned by the _GetFirstV86Page service. This supports virtual devices that
use the _Allocate_Global_V86_Data_Area service. Mapping a region which spans
across the first V86 page is not allowed. Mapping pages in this region to
other addresses can easily crash the system and should be avoided.
 
Uses
 
EAX
 
See Also
 
_Allocate_Global_V86_Data_Area, _GetFirstV86Page, _GetNulPageHandle,
_LinMapIntoV86
 
 
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