Post by Himanshu Chauhan Post by ron minnich
The reason I ask about what you need is that on chromebooks the main
coreboot support came down to 'don't disable anything’.
I think its can’t just be disabled. Its just that kernel is not given
any knowledge about its existence. This is what I want to know. The
commercial BIOSes give an option of “enable VT-d” support. What do they
do when this option is selected? Can this be implemented in Coreboot?
This probably brings me to your next question of what is required. I
would spend some time to figure that out.
First thing, the firmware doesn't have to support it. It's only that
Intel chose _not_ to write per platform OS drivers and let the firm-
ware do the abstraction instead (I know a kernel that works pretty well
with VT-d even if there are no DMAR tables).
coreboot already handles VT-d support on some chipsets (GM45, Sandy/
Ivy Bridge come to mind). You can look how it's done there. If you are
lucky, you only need to add 20~30 lines to your chipset's code.
If your chipset needs special initialization, it's most probably docu-
mented in the BIOS Writer's Guide (BWG) or BIOS Specification. Though,
you need an NDA with Intel to get these.
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