servers/vm/mem_directphys.c

   1
   2 /* This file implements the methods of direct physical mapping.
   3  *
   4  * A direct physical mapping is done by accepting the physical
   5  * memory address and range from the caller and allowing direct
   6  * access to it. Most significantly, no physical memory is allocated
   7  * when it's mapped or freed when it's unmapped. E.g. device memory.
   8  */
   9
  10 #include "vm.h"
  11
  12 /* These functions are static so as to not pollute the
  13  * global namespace, and are accessed through their function
  14  * pointers.
  15  */
  16
  17 static int phys_reference(struct phys_region *pr);
  18 static int phys_unreference(struct phys_region *pr);
  19 static int phys_writable(struct phys_region *pr);
  20 static int phys_pagefault(struct vmproc *vmp, struct vir_region *region,
  21                         struct phys_region *ph, int write);
  22 static int phys_copy(struct vir_region *vr, struct vir_region *newvr);
  23
  24 struct mem_type mem_type_directphys = {
  25         .name = "physical memory mapping",
  26         .ev_reference = phys_reference,
  27         .ev_copy = phys_copy,
  28         .ev_unreference = phys_unreference,
  29         .writable = phys_writable,
  30         .ev_pagefault = phys_pagefault
  31 };
  32
  33 static int phys_reference(struct phys_region *pr)
  34 {
  35         panic("%s", __FUNCTION__);
  36         return OK;
  37 }
  38
  39 static int phys_unreference(struct phys_region *pr)
  40 {
  41         return OK;
  42 }
  43
  44 static int phys_pagefault(struct vmproc *vmp, struct vir_region *region,
  45                         struct phys_region *ph, int write)
  46 {
  47         phys_bytes arg = region->param.phys, phmem;
  48         assert(arg != MAP_NONE);
  49         assert(ph->ph->phys == MAP_NONE);
  50         phmem = arg + ph->offset;
  51         assert(phmem != MAP_NONE);
  52         ph->ph->phys = phmem;
  53         return OK;
  54 }
  55
  56 static int phys_writable(struct phys_region *pr)
  57 {
  58         assert(pr->ph->refcount > 0);
  59         return pr->ph->phys != MAP_NONE;
  60 }
  61
  62 void phys_setphys(struct vir_region *vr, phys_bytes phys)
  63 {
  64         vr->param.phys = phys;
  65 }
  66
  67 static int phys_copy(struct vir_region *vr, struct vir_region *newvr)
  68 {
  69         newvr->param.phys = vr->param.phys;
  70
  71         return OK;
  72 }