Change in ...coreboot[master]: Documentation: Add arch x86

[Patrick Rudolph (Code Review)]

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/30056

Change subject: Documentation: Add arch x86
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Documentation: Add arch x86

Describe state and assuptions made about x86_64 support.

Change-Id: I308a09b0eac269afd30df95ed3ea195238a6cfbe
Signed-off-by: Patrick Rudolph 
---
M Documentation/arch/index.md
A Documentation/arch/x86/index.md
2 files changed, 33 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/56/30056/1

diff --git a/Documentation/arch/index.md b/Documentation/arch/index.md
index c3b080e..a0f1050 100644
--- a/Documentation/arch/index.md
+++ b/Documentation/arch/index.md
@@ -6,3 +6,6 @@
 ## RISC-V

- [RISC-V documentation](riscv/index.md)
+
+## x86
+- [x86 documentation](x86/index.md)
diff --git a/Documentation/arch/x86/index.md b/Documentation/arch/x86/index.md
new file mode 100644
index 0000000..b77a34b
--- /dev/null
+++ b/Documentation/arch/x86/index.md
@@ -0,0 +1,30 @@
+# 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:
+* 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
+
+## 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