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cpu/x86/Kconfig: Mark 64bit support as stable

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With SMM holding page tables itself, we can consider SMM support stable
and safe enough for general use.

Also update the respective documentation.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: Ifcf0a1a5097a2d7c064bb709ec0b09ebee13a47d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80338
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
This commit is contained in:
Arthur Heymans
2024-02-02 19:35:13 +01:00
committed by Martin L Roth
parent ee83be4d75
commit d293b20b84
18 changed files with 25 additions and 34 deletions
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13
Documentation/arch/x86/index.md
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@@ -9,9 +9,7 @@ x86 PAE support <pae.md>
```
## State of x86_64 support
At the moment there's only experimental x86_64 support.
The `emulation/qemu-i440fx` and `emulation/qemu-q35` boards do support
*ARCH_RAMSTAGE_X86_64* , *ARCH_POSTCAR_X86_64* and *ARCH_ROMSTAGE_X86_64*.
Some SOCs now support 64bit mode. Search for HAVE_X86_64_SUPPORT in Kconfig.
In order to add support for x86_64 the following assumptions were made:
* The CPU supports long mode
@@ -19,7 +17,6 @@ In order to add support for x86_64 the following assumptions were made:
* 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
* x86 payloads are loaded below 4GiB in physical memory and are jumped
to in *protected mode*
@@ -62,7 +59,6 @@ QEMU Q35 <../../mainboard/emulation/qemu-q35.md>
1. Fine grained page tables for SMM:
* Must not have execute and write permissions for the same page.
* Must allow only that TSEG pages can be marked executable
* Must reside in SMRAM
2. Support 64bit PCI BARs above 4GiB
3. Place and run code above 4GiB
@@ -70,13 +66,10 @@ QEMU Q35 <../../mainboard/emulation/qemu-q35.md>
* Fix compilation errors
* Test how well CAR works with x86_64 and paging
* Improve mode switches
* Test libgfxinit / VGA Option ROMs / FSP
## Known bugs on real hardware
## Known problems on real hardware
According to Intel x86_64 mode hasn't been validated in CAR environments.
Until now it could be verified on various Intel platforms and no issues have
been found.
Running VGA rom directly fails. Yabel works fine though.
## Known bugs on KVM enabled qemu