[coreboot-gerrit] Change in coreboot[master]: Documentation: Add TODOs for secure SMM when using x86_64

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/42982 )

Change subject: Documentation: Add TODOs for secure SMM when using x86_64
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Documentation: Add TODOs for secure SMM when using x86_64

Change-Id: I157238f18bc1c2eba0adc0b87caa9adaf3fc5d38
Signed-off-by: Patrick Rudolph 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42982
Tested-by: build bot (Jenkins) 
Reviewed-by: Arthur Heymans 
Reviewed-by: Raul Rangel 
---
M Documentation/arch/x86/index.md
1 file changed, 9 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved
  Raul Rangel: Looks good to me, approved

diff --git a/Documentation/arch/x86/index.md b/Documentation/arch/x86/index.md
index 536dea3..30dcc10 100644
--- a/Documentation/arch/x86/index.md
+++ b/Documentation/arch/x86/index.md
@@ -49,6 +49,15 @@
 * Add assembly code to return to protected mode - *TODO*
 * Implement reference code for mainboard `emulation/qemu-q35` - *TODO*

+## Future work
+
+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
+
 ## Porting other boards
 * Fix compilation errors
 * Test how well CAR works with x86_64 and paging