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Diffstat (limited to 'Documentation/arch/x86')
| -rw-r--r-- | Documentation/arch/x86/index.md | 32 |
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* |