Linux Kernel Memory - 4

PCI devices have access to three address spaces;
PCI I/O, PCI Memory (used by the PCI initialization code) and PCI Configuration space (used by the device drivers).

virt_to_phys(virt_addr) = __pa(virt_addr) = Virt Addr - 0xC0000000
phys_to_virt(phy_addr) = __va(phy_addr) = Phy Addr + 0xC0000000

Check the given physical memory is in RAM:
if (phy_addr < virt_to_phys(high_memory)) {
    The given physical memory is in RAM
}

ioremap:
area = get_vm_area(size, VM_IOREMAP); (return a free area in virtual addres space)
remap_area_pages(virt_addr, phys_addr, size, flags); (update PGD, PMD and PTE table)

vmalloc:
area = get_vm_area(size, VM_ALLOC); (return a free area in virtual addres space)
vmalloc_area_pages(virt_addr, size, flags, prot); (update PGD, PMD and PTE table)

iounmap: vfree:
vmfree_area_pages(virt_addr, size); (update PGD, PMD and PTE table)

How does ioremap and vmalloc relatted???

request_mem_region (Phy Addr, Length, Name);
pci_request_regions (PDev, Name); (to update "/proc/iomem")

------------------------------------------------
ethtool –i eth0
  driver: e1000
  version: 7.0.38
  firmware-version: N/A
  bus-info: 02:03.0

./pcidump /proc/bus/pci/02/03.0
  …
  B0 Base Address 0: fc200004
  B1 Base Address 1: 00000000
  B2 Base Address 2: 00000000
  B3 Base Address 3: 00000000
  B4 Base Address 4: 00003001
  B5 Base Address 5: 00000000
  …

cat /proc/iomem
 …
 c2e2a000-c3f00000 : Bigphysarea
 fc100000-fc4fffff : PCI Bus #01
  fc200000-fc3fffff : PCI Bus #02
    fc200000-fc21ffff : PCI device 8086:1010
      fc200000-fc21ffff : e1000
    fc300000-fc3fffff : PCI Bus #03
      fc300000-fc30ffff : PCI device 170b:0100
  fc400000-fc4fffff : PCI Bus #04
    fc400000-fc41ffff : PCI device 8086:1079
      fc400000-fc41ffff : e1000
 fc500000-fc500fff : PCI device 1002:4752
 …
------------------------------------------------

Reference:
http://tldp.org/LDP/tlk/dd/pci.html
http://linuxgazette.net/issue83/thangaraju.html