On Thu, Aug 13, 2026 at 4:15 AM ron minnich <[email protected]> wrote:
> you can not disable SMM no matter how early in the boot process you get.
>
> The memory it runs from is walled off by registers you can not set.
> It is enabled by write-once (sticky) bits.
> The interrupts vector to firmware.
>
> Nope, you can't just disable that code at boot time. It's been enabled long
> before.
Well, you kinda sorta maybe can, but only if you can intercede on the
boot process early enough. We do our level best to render it inert,
and we're pretty sure that we have because we control the x86
processors from the time they come out of reset, and we don't use UEFI
or ACPI (or them resident on our systems anywhere) and so we configure
the OS to intercept SMIs, but there's no guarantee about the state of
things from x86 reset because all of the little cores hidden inside of
the SoC complex can do all sorts of weird stuff before x86 even starts
(and of course, independent of SMM, it's still possible to talk to
those things if you can get down to a deep enough level).
But if you're stuck with a standard UEFI-based systems? You're out of luck.
- Dan C.
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