pci device's memory region and physical memory region

["Bao zhao" <paozhaokeats@xxxxxxxxxxx>]

  It seems that PCI device's memory region always use address between 
3GB-4GB, so if I have 4GB physical memory , then some of physical memory 
region would be hidden by PCI device's memory region , it cannot be used by 
kernel.
  If I make mistakes ,please point to me,Thaks!

some data  from lspci command

00:04.0 Ethernet controller: Intel Corp. 82557/8/9 [Ethernet Pro 100] (rev 
08)
       Subsystem: Dell Computer Corporation: Unknown device 0106
       Flags: bus master, medium devsel, latency 32, IRQ 19
       Memory at fe203000 (32-bit, non-prefetchable)
       I/O ports at ecc0 [size=64]
       Memory at fe000000 (32-bit, non-prefetchable) [size=1M]
       Capabilities: [dc] Power Management version 2

00:06.0 SCSI storage controller: Adaptec AHA-2940U2/U2W / 7890/7891 (rev 01)
       Subsystem: Dell Computer Corporation: Unknown device 0106
       Flags: bus master, medium devsel, latency 32, IRQ 18
       BIST result: 00
       I/O ports at e800 [disabled] [size=fe100000]
       Memory at fe202000 (64-bit, non-prefetchable) [size=4K]
       Expansion ROM at 00020000 [disabled]
       Capabilities: [dc] Power Management version 1

00:0e.0 VGA compatible controller: ATI Technologies Inc Rage XL (rev 27) 
(prog-if 00 [VGA])
       Subsystem: Dell Computer Corporation: Unknown device 0106
       Flags: bus master, VGA palette snoop, stepping, medium devsel, 
latency 32
       Memory at fd000000 (32-bit, non-prefetchable)
       I/O ports at e400 [size=256]
       Memory at fe201000 (32-bit, non-prefetchable) [size=4K]
       Capabilities: [5c] Power Management version 2

Best Regards

Bao Zhao

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