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-rw-r--r--Documentation/arch/x86/index.md32
1 files changed, 22 insertions, 10 deletions
diff --git a/Documentation/arch/x86/index.md b/Documentation/arch/x86/index.md
index 73c982385a..462e7e6c6e 100644
--- a/Documentation/arch/x86/index.md
+++ b/Documentation/arch/x86/index.md
@@ -16,24 +16,36 @@ In order to add support for x86_64 the following assumptions are made:
* 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
+## Assuptions for all stages using the reference implementation
+* 0-4GiB are identity mapped using 2MiB-pages as WB
* Memory above 4GiB isn't accessible
-* pagetables reside in _pagetables
-* Romstage must install new pagetables in CBMEM after RAMINIT
+* page tables reside in memory mapped ROM
+* A stage can install new page tables in RAM
-## Assuptions for ARCH_RAMSTAGE_X86_64 reference implementation
-* Romstage installed pagetables according to memory layout
-* Memory above 4GiB is accessible
+## Page tables
+Page tables are generated by a tool in `util/pgtblgen/pgtblgen`. It writes
+the page tables to a file which is then included into the CBFS as file called
+`pagetables`.
+
+To generate the static page tables it must know the physical address where to
+place the file.
+
+The page tables contains the following structure:
+* PML4E pointing to PDPE
+* PDPE with *$n* entries each pointing to PDE
+* *$n* PDEs with 512 entries each
+
+At the moment *$n* is 4, which results in identity mapping the lower 4 GiB.
## 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 rmodule support - *DONE*
* Add x86_64 exception handlers - *TODO*
-* Setup page tables for long mode - *TODO*
-* Add assembly code for long mode - *TODO*
+* Setup page tables for long mode - *DONE*
+* Add assembly code for long mode - *DONE*
+* Add assembly code for postcar stage - *TODO*
* Add assembly code to return to protected mode - *TODO*
* Implement reference code for mainboard `emulation/qemu-q35` - *TODO*