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include vmm.inc
 
VMMcall _MapFreePhysReg, <LinPgNum, nPages, flags>
 
or      eax,eax         ; nonzero if mapped, zero if error
je      not_mapped
 
The _MapFreePhysReg service maps one or more physical pages into a free
physical region. The service maps physical pages currently in the free list
to the specified pages in the region.
 
Parameter  Description
────────────────────────────────────────────────────────────────────────────
 
LinPgNum   Specifies the linear page number of the first page to map. The
           page must be in a free physical region previously created using
           the _PageAllocate service. A linear page number is a linear
           address shifted right by 12 bits right.
 
nPages     Specifies number of pages to map. All pages must be within the
           free physical region.
 
flags      Specifies the operation flags. This parameter can be the
           following value:
 
           Value      Meaning
           ─────────────────────────────────────────────────────────────────
           PageFixed  Maps the specified pages as fixed pages, permanently
                      locking the pages at the specified address. If this
                      value is not given, the pages are not fixed. Virtual
                      devices never return fixed pages to the system.
 
           All other values are reserved.
 
Return Value
 
The EAX register contains a nonzero value if the service is successful.
Otherwise, EAX contains returns zero specifying an invalid linear page
number, an invalid range of pages, part of the page range already present,
insufficient number of pages on free list, or an invalid use of the
PageFixed value.
 
Comments
 
This service is intended to be used in a free-physical-region callback
procedure installed using the _SetFreePhysRegCalBk service. Virtual devices
should not call this service until after the Sys_VM_Init message or the
Init_Complete message has been received.
 
The PageFixed value allows a virtual device to maintain a cache of memory
which has a minimum size. The virtual device maps a predetermined number of
pages using the PageFixed value to ensure that this cache has its minimum
size. The virtual device never unmaps these pages. The virtual device maps
any additional pages without using the PageFixed value. This allows these
pages to be unmapped later. Occasionally, there may be too few physical
pages to attain the minimum cache size. The virtual device must be prepared
to handle this condition.
 
Uses
 
EAX
 
See Also
 
_SetFreePhysRegCalBk, _UnmapFreePhysReg
 
 
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