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OvmfPkg/README: Add information about OVMF flash layout 

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14836 6f19259b-4bc3-4df7-8a09-765794883524
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Jordan Justen 2013-11-12 18:34:28 +00:00 committed by jljusten
parent 9a08997862
commit e58e5bcd23
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@ -179,6 +179,43 @@ longer.)
VirtioNetDxe | x
Intel PROEFI | x
=== OVMF Flash Layout ===
Like all current IA32/X64 system designs, OVMF's firmware
device (rom/flash) appears in QEMU's physical address space
just below 4GB (0x100000000).
The layout of the firmware device in memory looks like:
+--------------------------------------- 4GB (0x100000000)
| VTF0 (16-bit reset code) and OVMF SEC
| (SECFV)
+--------------------------------------- varies based on flash size
|
| Compressed main firmware image
| (FVMAIN_COMPACT)
|
+--------------------------------------- base + 0x20000
| Fault-tolerant write (FTW)
| Spare blocks (64KB/0x10000)
+--------------------------------------- base + 0x10000
| FTW Work block (4KB/0x1000)
+--------------------------------------- base + 0x0f000
| Event log area (4KB/0x1000)
+--------------------------------------- base + 0x0e000
| Non-volatile variable storage
| area (56KB/0xe000)
+--------------------------------------- base address
OVMF supports building a 1MB or a 2MB flash image. The base address for
a 1MB image in QEMU physical memory is 0xfff00000. The base address for
a 2MB image is 0xffe00000.
The code in SECFV locates FVMAIN_COMPACT, and decompresses the
main firmware (MAINFV) into RAM memory at address 0x800000. The
remaining OVMF firmware then uses this decompressed firmware
volume image.
=== UNIXGCC Debug ===
If you build with the UNIXGCC toolchain, then debugging will be disabled