Ah... am I right in thinking the exploit runs when cores other than the first 
are being started?

Doesn't the boot firmware -- BIOS/UEFI -- have control over whether SMM is 
started? That's what I was thinking.

On Wed, Aug 12, 2026, at 11:57 PM, ron minnich 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.
>
> On Wed, Aug 12, 2026 at 11:01 AM Ethan Azariah <[email protected]> wrote:
>
>> On Sat, Aug 8, 2026, at 3:49 PM, ron minnich wrote:
>> > for all of you who ever suffered with smm, here's another trivial break.
>> I
>> > like this one a lot.
>> >
>> > https://github.com/xoreaxeaxeax/smiiiiiiiiiiiiiiii
>> >
>> > "It turns out that you can break SMM — the secure, ultra privileged
>> > execution environment running invisibly in the background of every x86
>> CPU
>> > — with nothing more than an obscenely long-running machine instruction."
>> >
>> > That was easy. Usually it took more effort.
>> 
>> Entertaining, but if you can inject code into that point of the boot
>> process, can't you just disable the code which enables SMM?

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