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coreboot-kgpe-d16/Documentation/arch/x86/index.md
Patrick Rudolph c1b7e8a60b cpu/x86/pae/pgtbl: Add memset with PAE 
To clear all DRAM on x86_32, add a new method that uses PAE to access
more than 32bit of address space.
Add Documentation as well.

Required for clearing all system memory as part of security API.

Tested on wedge100s:
 Takes less than 2 seconds to clear 8GiB of DRAM.
Tested on P8H61M-Pro:
 Takes less than 1 second to clear 4GiB of DRAM.

Change-Id: I00f7ecf87b5c9227a9d58a0b61eecc38007e1a57
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31549
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2019-07-02 08:45:50 +00:00

1.6 KiB
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x86 architecture documentation

This section contains documentation about coreboot on x86 architecture.

State of x86_64 support

At the moment there's no single board that supports x86_64 or to be exact ARCH_RAMSTAGE_X86_64 and ARCH_ROMSTAGE_X86_64.

In order to add support for x86_64 the following assumptions are made:

  • The CPU supports long mode
  • All memory returned by malloc must be below 4GiB in physical memory
  • All code that is to be run must be below 4GiB in physical memory
  • The high dword of pointers is always zero
  • The reference implementation is qemu
  • The CPU supports 1GiB hugepages

Assuptions for ARCH_ROMSTAGE_X86_64 reference implementation

  • 0-4GiB are identity mapped using 1GiB huge-pages
  • Memory above 4GiB isn't accessible
  • pagetables reside in _pagetables
  • Romstage must install new pagetables in CBMEM after RAMINIT

Assuptions for ARCH_RAMSTAGE_X86_64 reference implementation

  • Romstage installed pagetables according to memory layout
  • Memory above 4GiB is accessible

Steps to add basic support for x86_64

  • Add x86_64 toolchain support - DONE
  • Fix compilation errors - DONE
  • Fix linker errors - TODO
  • Add x86_64 rmodule support - ONGERRIT
  • Add x86_64 exception handlers - TODO
  • Setup page tables for long mode - TODO
  • Add assembly code for long mode - TODO
  • Add assembly code to return to protected mode - TODO
  • Implement reference code for mainboard emulation/qemu-q35 - TODO

Porting other boards

  • Fix compilation errors
  • Test how well CAR works with x86_64 and paging
  • Improve mode switches
  • Test libgfxinit / VGA Option ROMs / FSP