- Improve help texts for option ROM initialization methods

- disallow REAL_MODE method if ARCH_X86 is not set.

Signed-off-by: Stefan Reinauer <stepan@coresystems.de>
Acked-by: Stefan Reinauer <stepan@coresystems.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5072 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

diff --git a/src/devices/Kconfig b/src/devices/Kconfig
index 96084f95b2c3806038b2752572c7ce9b8ec0a0ca..f247d89926e10f2485ea08c96570a212f9c60515 100644 (file)
--- a/src/devices/Kconfig
+++ b/src/devices/Kconfig
@@ -42,32 +42,50 @@ config PCI_ROM_RUN
          Examples include IDE/SATA controller option ROMs and option ROMs
          for network cards (NICs).
 
-# TODO: Describe YABEL vs. x86emu differences in more detail.
 choice
        prompt "Option ROM execution type"
-       default PCI_OPTION_ROM_RUN_REALMODE
+       default PCI_OPTION_ROM_RUN_YABEL if !ARCH_X86
+       default PCI_OPTION_ROM_RUN_REALMODE if ARCH_X86
        depends on PCI_ROM_RUN || VGA_ROM_RUN
 
 config PCI_OPTION_ROM_RUN_REALMODE
        prompt "Real mode"
        bool
+       depends on ARCH_X86
        help
          If you select this option, PCI option ROMs will be executed
-         natively on the hardware (a 32bit x86 system is required).
+         natively on the CPU in real mode. No CPU emulation is involved,
+         so this is the fastest, but also the least secure option.
+         (only works on x86/x64 systems)
 
-config PCI_OPTION_ROM_RUN_YABEL
-       prompt "YABEL"
+config PCI_OPTION_ROM_RUN_X86EMU
+       prompt "x86emu"
        bool
        help
-         If you select this option, the YABEL BIOS emulator will be used to
-         execute PCI option ROMs.
+         If you select this option, the x86emu CPU emulator will be used to
+         execute PCI option ROMs. 
+         When choosing this option, x86emu will pass through all hardware
+         accesses to memory and IO devices to the underlying memory and IO
+         addresses. While this option prevents option ROMs from doing dirty
+         tricks with the CPU (such as installing SMM modules or hypervisors),
+         they can still access all devices in the system.
+         Choosing x86emu, option ROM execution is slower than native execution
+         in real mode, but faster than the full system emulation YABEL
+         This is the default choice for non-x86 systems.
 
-config PCI_OPTION_ROM_RUN_X86EMU
-       prompt "x86emu"
+config PCI_OPTION_ROM_RUN_YABEL
+       prompt "YABEL"
        bool
        help
-         If you select this option, the x86emu BIOS emulator will be used to
+         If you select this option, the YABEL system emulator will be used to
          execute PCI option ROMs.
+         YABEL consists of two parts: It uses x86emu for the CPU emulation and
+         additionally provides a PC system emulation that filters bad device and
+         memory access (such as PCI config space access to other devices than the
+         initialized one).
+         This option best prevents option ROMs from doing dirty tricks with the 
+         system (such as installing SMM modules or hypervisors), but it is also
+         significantly slower than the other option ROM initialization methods.
 
 endchoice